ESLint Blog

ESLint v9.18.0 released

2025-01-10T00:00:00Z

Highlights

Stable TypeScript configuration file support

In August of the previous year, ESLint launched support for TypeScript configuration files as an experimental feature. In order to use a TypeScript configuration file like eslint.config.ts, users had to specify the unstable_ts_config flag in the command line, e.g.

npx eslint --flag unstable_ts_config

Following an experimental period of several months, during which there were no specific complaints and only minor adjustments, we have made the decision to officially implement support for TypeScript configuration files as a stable feature. Starting with ESLint v9.18.0, TypeScript configuration files with extensions .ts, .mts and .cts can be used like regular JavaScript configuration files. If you are upgrading from a previous version of ESLint, be sure to remove the unstable_ts_config flag from the command.

Note that in order to use a TypeScript configuration file in Node.js, you still need to have jiti installed in version 2.0 or higher. For Deno and Bun, no additional dependency is necessary. See the documentation about TypeScript Configuration Files for more information about this feature.

`no-shadow-restricted-names` checks imports and class names

The no-shadow-restricted-names rule will now check for restricted names also in import declarations and in class names, for example:

import undefined from "foo";

class NaN {}

Playground Link

This rule was added in ESLint v0.1.4 to report on variables and functions with names that could be confusing to developers like NaN or undefined. As JavaScript evolved, new syntactic constructs were introduced that could accept the same problematic names. These newer cases are now detected and reported by the rule.

Allowed method names in `no-config` problems

The no-console-rule has been updated to indicate the name of methods that are explicitly configured as allowed when reporting a problem. This can help developers to find an acceptable alternative to problem reported by this rule.

Consider the following case where no-console is configured to allow only the warn and error methods.

/* eslint no-console: ["error", { allow: ["warn", "error"] }] */

console.log("Some text.");

Previously, the rule would report a problem with the generic message “Unexpected console statement.” In ESLint v9.18.0, the message reads “Unexpected console statement. Only these console methods are allowed: warn, error.”

Playground Link

Features

e84e6e2 feat: Report allowed methods for no-console rule (#19306) (Anna Bocharova)
8efc2d0 feat: unflag TypeScript config files (#19266) (Francesco Trotta)
87a9352 feat: check imports and class names in no-shadow-restricted-names (#19272) (Milos Djermanovic)

Bug Fixes

da768d4 fix: correct overrideConfigFile type (#19289) (Francesco Trotta)

Documentation

d9c23c5 docs: replace var with const in rule examples (#19325) (Tanuj Kanti)
8e1a898 docs: add tabs to cli code blocks (#18784) (Jay)
f3aeefb docs: rewrite using let and const in rule examples (#19320) (PoloSpark)
0b680b3 docs: Update README (GitHub Actions Bot)
98c86a9 docs: Edit this page button link to different branches (#19228) (Tanuj Kanti)
6947901 docs: remove hardcoded edit link (#19323) (Milos Djermanovic)
03f2f44 docs: rewrite var with const in rules examples (#19317) (Thiago)
26c3003 docs: Clarify dangers of eslint:all (#19318) (Nicholas C. Zakas)
c038257 docs: add eqeqeq in related rules to no-eq-null (#19310) (루밀LuMir)
89c8fc5 docs: rewrite examples with var using let and const (#19315) (Amaresh S M)
db574c4 docs: add missing backticks to no-void (#19313) (루밀LuMir)
8d943c3 docs: add missing backticks to default-case-last (#19311) (루밀LuMir)
36ef8bb docs: rewrite examples with var using let and const (#19298) (Amaresh S M)
1610c9e docs: add missing backticks to no-else-return (#19309) (루밀LuMir)
df409d8 docs: Update README (GitHub Actions Bot)
2e84213 docs: Fix Horizontal Scroll Overflow in Rule Description on Mobile View (#19304) (Amaresh S M)
6e7361b docs: replace var with let and const in rule example (#19302) (Tanuj Kanti)
069af5e docs: rewrite var using const in rule examples (#19303) (Kim GyeonWon)
064e35d docs: remove ‘I hope to’ comments from scope-manager-interface (#19300) (Josh Goldberg ✨)
8e00305 docs: replace var with const in rule examples (#19299) (Tanuj Kanti)
a559009 docs: Add warning about extending core rules (#19295) (Nicholas C. Zakas)
0bfdf6c docs: Update README (GitHub Actions Bot)
ce0b9ff docs: add navigation link for code explorer (#19285) (Tanuj Kanti)
e255cc9 docs: add bluesky icon to footer (#19290) (Tanuj Kanti)
5d64851 docs: remove outdated info about environments (#19296) (Francesco Trotta)
eec01f0 docs: switch rule examples config format to languageOptions (#19277) (Milos Djermanovic)
b36ca0a docs: Fixing Focus Order by Rearranging Element Sequence (#19241) (Amaresh S M)
d122c8a docs: add missing backticks to sort-imports (#19282) (루밀LuMir)
0367a70 docs: update custom parser docs (#19288) (Francesco Trotta)
8c07ebb docs: add border-radius to hX:target selector styles (#19270) (루밀LuMir)
eff7c57 docs: add limitation section in no-loop-func (#19287) (Tanuj Kanti)
5db226f docs: add missing backticks in various parts of the documentation (#19269) (루밀LuMir)
789edbb docs: Update README (GitHub Actions Bot)
613c06a docs: mark rules that are frozen with ❄️ (#19231) (Amaresh S M)
43172ec docs: Update README (GitHub Actions Bot)
ac8b3c4 docs: fix description of overrideConfigFile option (#19262) (Milos Djermanovic)
bbb9b46 docs: Update README (GitHub Actions Bot)
995b492 docs: fix inconsistent divider in rule categories box (#19249) (Tanuj Kanti)
f76d05d docs: Refactor search result handling with better event listener cleanup (#19252) (Amaresh S M)
c5f3d7d docs: Update README (GitHub Actions Bot)

Chores

c52be85 chore: upgrade to @eslint/js@9.18.0 (#19330) (Francesco Trotta)
362099c chore: package.json update for @eslint/js release (Jenkins)
495aa49 chore: extract package name from package.json for public interface (#19314) (루밀LuMir)
6fe0e72 chore: update dependency @eslint/json to ^0.9.0 (#19263) (renovate[bot])

ESLint v9.17.0 released

2024-12-13T00:00:00Z

Highlights

`no-unused-vars` Suggestions

The no-unused-vars rule provides suggestions now! When the rule sees code with an unused variable like this:

const a = "Hello";
const b = "World!";
console.log(a);

It will now suggest removing the unused variable declaration:

const a = "Hello";

console.log(a);

Suggestions also work for more complex cases like unused function arguments, destructuring syntax, etc.

function avg(a, b, c) {
    return (a + b) / 2;
}

console.log(avg(12, 13, 25));

after the suggestion is applied becomes:

function avg(a, b) {
    return (a + b) / 2;
}

console.log(avg(12, 13, 25));

and

const [{ status, value, reason }] = await Promise.allSettled([promise1, promise2]);

if (status === "rejected") {
    throw reason;
}

after the suggestion becomes:

const [{ status, reason }] = await Promise.allSettled([promise1, promise2]);

if (status === "rejected") {
    throw reason;
}

no-unused-vars suggestions mark the completion of months of work. We will likely further improve and fine-tune this feature in future updates.

Nullish `message.fix` Allowed

Previously, if a processor returned a LintMessage with a fix property set to undefined or null, ESLint would crash with an unhelpful error message when trying to apply the autofix. This problem has been fixed in the current release.

Features

eed91d1 feat: add suggestions to no-unused-vars (#18352) (Tanuj Kanti)

Bug Fixes

67d683d fix: fix crash when message.fix is nullish (#19168) (ntnyq)
c618707 fix: ignore vars with non-identifier references in no-useless-assignment (#19200) (YeonJuan)

Documentation

3c22d2a docs: update yoda to Yoda in [yoda](/docs/rules/yoda).md for consistency (#19230) (루밀LuMir)
e0a2203 docs: add missing backticks to no-sequences (#19233) (루밀LuMir)
4cc4881 docs: Update README (GitHub Actions Bot)
3db6fdf docs: [no-await-in-loop] expand on benefits and inapplicability (#19211) (Kirk Waiblinger)
bf2a4f6 docs: add missing backticks to func-style (#19227) (루밀LuMir)
ba098bd docs: add missing header to prefer-spread (#19224) (루밀LuMir)
b607ae6 docs: update description of no-param-reassign (#19220) (루밀LuMir)
1eb424d docs: add missing backticks to prefer-destructuring (#19223) (루밀LuMir)
85998d1 docs: add missing backticks to no-unneeded-ternary (#19222) (루밀LuMir)
b75b32c docs: add missing backticks to no-new-func (#19219) (루밀LuMir)
a7700bc docs: add missing backticks to id-length (#19217) (루밀LuMir)
e2bb429 docs: add missing backticks to [complexity](/docs/rules/complexity).md (#19214) (루밀LuMir)
045d716 docs: add missing ) to id-denylist (#19213) (루밀LuMir)
7fe4114 docs: Update README (GitHub Actions Bot)
c743ba6 docs: add CSS language to no-restricted-syntax (#19208) (Milos Djermanovic)
1416d70 docs: add missing backticks to eqeqeq (#19207) (루밀LuMir)
b950c1b docs: add missing backticks to prefer-object-spread (#19206) (루밀LuMir)
8a941cb docs: update docs and description of require-unicode-regexp (#19205) (루밀LuMir)
cbab228 docs: Update README (GitHub Actions Bot)
f2257ce docs: update comments and description of no-script-url (#19203) (루밀LuMir)
365f0f4 docs: add missing backtick to default-case-last (#19202) (루밀LuMir)
e6b84f5 docs: add missing punctuation in document (#19161) (루밀LuMir)
c88708e docs: replace quote with backtick in description of for-direction (#19199) (루밀LuMir)
a76f233 docs: use higher contrast color tokens for code comments (#19187) (Josh Goldberg ✨)
db19502 docs: Update README (GitHub Actions Bot)

Chores

cc243c9 chore: upgrade to @eslint/js@9.17.0 (#19242) (Francesco Trotta)
84c5787 chore: package.json update for @eslint/js release (Jenkins)
4c4f53b chore: add missing backticks to flags.js (#19226) (루밀LuMir)
4b3132c chore: update dependency eslint-plugin-expect-type to ^0.6.0 (#19221) (renovate[bot])
9bf2204 chore: add type definitions for the eslint-config-eslint package (#19050) (Arya Emami)
ee8c220 chore: fix incorrect name property in integration-tutorial-code (#19218) (루밀LuMir)
cca801d chore: Upgrade cross-spawn to 7.0.6 (#19185) (folortin)

ESLint v9.16.0 released

2024-11-29T00:00:00Z

Highlights

`ignoreComputedKeys` option for `sort-keys`

This release adds a new boolean option ignoreComputedKeys to the sort-keys rule. ignoreComputedKeys allows a more consistent sorting of properties with non-computed names by treating computed keys as group separators rather than part of a group. The following example shows the expected sorting of properties in an object literal without the ignoreComputedKeys option.

with ignoreComputedKeys: false (default)

const obj = { a: 10, b: 20, [c]: 7.5, d: 15 };

When ignoreComputedKeys is set to true, the computed key c can appear anywhere in the literal, as long as the other groups of properties are sorted.

with ignoreComputedKeys: true

const obj = { a: 10, b: 20, [c]: 7.5, d: 15 };

const obj = { d: 15, [c]: 7.5, a: 10, b: 20 };

const obj = { a: 10, b: 20, d: 15, [c]: 7.5 };

etc.

Language-agnostic `no-restricted-syntax`

Another enhancement in this release is the ability to use the no-restricted-syntax rule with any language. This was already possible in previous releases, but now usage with language plugins is officially supported and documented.

When linting JSON files with the @eslint/json plugin, a config that warns about the usage of null could look like this:

import json from "@eslint/json";

export default [
    {
        files: ["**/*.json"],
        language: "json/json",
        plugins: {
            json,
        },
        rules: {
            "no-restricted-syntax": [
                "warn",
                "Null" // AST selector for `null`
            ],
        },
    },
];

If you would like to restrict syntax in your project based on AST selectors but you’re unsure what nodes represent a particular code, we recommend using Code Explorer.

Features

8f70eb1 feat: Add ignoreComputedKeys option in sort-keys rule (#19162) (Milos Djermanovic)

Documentation

9eefc8f docs: fix typos in use-isnan (#19190) (루밀LuMir)
0c8cea8 docs: switch the order of words in no-unreachable (#19189) (루밀LuMir)
0c19417 docs: add missing backtick to no-async-promise-executor (#19188) (루밀LuMir)
8df9276 docs: add backtick in -0 in description of no-compare-neg-zero (#19186) (루밀LuMir)
7e16e3f docs: fix caseSensitive option’s title of sort-keys (#19183) (Tanuj Kanti)
0c6b842 docs: fix typos in migration-guide.md (#19180) (루밀LuMir)
353266e docs: fix a typo in debug.md (#19179) (루밀LuMir)
5ff318a docs: delete unnecessary horizontal rule(---) in nodejs-api (#19175) (루밀LuMir)
576bcc5 docs: mark more rules as handled by TypeScript (#19164) (Tanuj Kanti)
742d054 docs: note that no-restricted-syntax can be used with any language (#19148) (Milos Djermanovic)

Chores

feb703b chore: upgrade to @eslint/js@9.16.0 (#19195) (Francesco Trotta)
df9bf95 chore: package.json update for @eslint/js release (Jenkins)
f831893 chore: add type for ignoreComputedKeys option of sort-keys (#19184) (Tanuj Kanti)
3afb8a1 chore: update dependency @eslint/json to ^0.8.0 (#19177) (Milos Djermanovic)
1f77c53 chore: add repository.directory property to package.json (#19165) (루밀LuMir)
d460594 chore: update dependency @arethetypeswrong/cli to ^0.17.0 (#19147) (renovate[bot])
45cd4ea refactor: update default options in rules (#19136) (Milos Djermanovic)

ESLint v9.15.0 released

2024-11-15T00:00:00Z

This release updates the @eslint/plugin-kit dependency to the latest version 0.2.3 which includes the fix for security advisory GHSA-7q7g-4xm8-89cq.

Highlights

`meta.defaultOptions`

Rules can now specify default options. ESLint will recursively merge any user-provided options elements on top of the default elements.

This feature makes it easier to work with options in rules.

// my-rule.js
export default {
    meta: {
        defaultOptions: [{
            alias: "basic",
            ignoreClassFields: false
        }],
        schema: [{
            type: "object",
            properties: {
                alias: {
                    type: "string"
                },
                ignoreClassFields: {
                    type: "boolean"
                }
            },
            additionalProperties: false
        }]
    },
    create(context) {

        // `context.options` is guaranteed to be an array with a single object
        // that has a string property `alias` and a boolean property `ignoreClassFields`.
        // If the rule is enabled with no options specified in the configuration file,
        // `alias` will be `"basic"`, and `ignoreClassFields` will be `false`.
        const [{ alias, ignoreClassFields }] = context.options;

        return { /* ... */ };
    }
};

This feature also allows document generators, other tools and integrations, and end users to easily find the default options for rules.

Other notable changes

Custom languages can now provide the normalizeLanguageOptions(languageOptions) method. The return value will be used as languageOptions when calling parse(), createSourceCode(), and applyLanguageOptions() methods and as the value of context.languageOptions property in rules.
The no-useless-computed-key rule now fully supports object destructuring patterns.

Features

01557ce feat: Implement Language#normalizeLanguageOptions() (#19104) (Nicholas C. Zakas)
2edc0e2 feat: add meta.defaultOptions (#17656) (Josh Goldberg ✨)
bdec50e feat: fix no-useless-computed-key false negative with __proto__ (#19123) (Milos Djermanovic)
3087c9e feat: add meta object to @eslint/js plugin (#19095) (Francesco Trotta)

Bug Fixes

fd33f13 fix: update types for no-restricted-imports rule (#19060) (Nitin Kumar)
bd35098 fix: switch away from Node.js node:assert and AssertionError (#19082) (Josh Goldberg ✨)
9db5b15 fix: unsafe report for no-lonely-if (#19087) (Abraham Guo)
68fa497 fix: ignore files on a different drive on Windows (#19069) (Francesco Trotta)
4ce625a fix: upgrade @humanwhocodes/retry@0.4.1 to avoid debug logs (#19102) (Milos Djermanovic)

Documentation

d927920 docs: fix styles in no-js mode (#18916) (Tanuj Kanti)
09bc2a8 docs: Update README (GitHub Actions Bot)
39089c8 docs: add no-useless-computed-key examples with object patterns (#19109) (Milos Djermanovic)
895c60f docs: add missing messageId property and suggestion properties (#19122) (fnx)
298625e docs: Change CLI -c to use flat config (#19103) (Nicholas C. Zakas)
522d8a3 docs: add deprecation on indent, quotes and semi rule types (#19090) (Marco Pasqualetti)

Chores

2967d91 chore: upgrade @eslint/js@9.15.0 (#19133) (Milos Djermanovic)
b441bee chore: package.json update for @eslint/js release (Jenkins)
7d6bf4a chore: upgrade @eslint/core@0.9.0 (#19131) (Milos Djermanovic)
902e707 chore: upgrade @eslint/plugin-kit@0.2.3 (#19130) (Milos Djermanovic)
5ff6c1d chore: bump cross-spawn (#19125) (Ian Bobinac)
cceccc7 chore: update dependency @eslint/json to ^0.6.0 (#19117) (renovate[bot])
0da3f73 chore: update algolia referrer (#19114) (Strek)
4f08332 ci: unpin trunk-io/trunk-action (#19108) (Francesco Trotta)
6b75683 perf: optimize text-table by replacing regex with trimEnd (#19061) (Nitin Kumar)

ESLint v9.14.0 released

2024-11-01T00:00:00Z

Highlights

Support for Import Attributes

We have updated ESLint to fully support the ECMAScript 2025 Import Attributes syntax. This syntax allows module import statements and dynamic imports to pass on more information alongside the module specifier. Host environments can use this information to modify import behavior and support additional types of modules. For example, when type: "json" is specified, modules are treated as JSON Modules.

import json from "./foo.json" with { type: "json" };

import("foo.json", { with: { type: "json" } });

The updates in ESLint include parsing and ensuring that naming convention rules do not apply to import attribute keys as they are defined by the ECMAScript Specification or by the host environment and thus users have no control over their naming.

Please note that deprecated formatting rules will not be updated to support this syntax. If you are still using core formatting rules, we recommend switching to a source code formatter. Alternatively, you can replace core formatting rules with corresponding rules from @stylistic/eslint-plugin-js.

Support for RegExp Modifiers

We have updated ESLint to fully support the ECMAScript 2025 Regular Expression Pattern Modifiers. This feature allows you to change the currently active RegExp flags within a subexpression.

const regex1 = /^(?i:[a-z])[a-z]$/;

const regex2 = /^[a-z](?-i:[a-z])$/i;

The updates in ESLint include parsing and ensuring that rules related to regular expressions are behaving as expected.

Improved configuration file lookup performance

In v9.13.0, we introduced changes to how configuration files were looked up. Some of these changes negatively impact ESLint’s runtime performance due to incorrect caching of configuration file data. This was visible primarily using the default configuration lookup algorithm, where a 20-30% performance degradation was reported (the new algorithm, accessed via --flag unstable_config_lookup_from_file, has different performance characteristics and didn’t show the same negative performance impact in our tests).

We’ve now fixed the configuration file lookup caching behavior both in the default algorithm and the experimental algorithm so you should improved performance when you upgrade from v9.13.0.

Features

3fa009f feat: add support for Import Attributes and RegExp Modifiers (#19076) (Milos Djermanovic)
b0faee3 feat: add types for the @eslint/js package (#19010) (Nitin Kumar)

Bug Fixes

24d0172 fix: enable retry concurrency limit for readFile() (#19077) (Nicholas C. Zakas)
b442067 fix: Don’t crash when directory is deleted during traversal. (#19067) (Nicholas C. Zakas)
d474443 fix: avoid call stack overflow while processing globs (#19035) (Livia Medeiros)

Documentation

151c965 docs: update context.languageOptions.parser description (#19084) (Nitin Kumar)
dc34f94 docs: Update README (GitHub Actions Bot)
f16e846 docs: Update README (GitHub Actions Bot)
ee0a77e docs: change link from @types/eslint to lib/types (#19049) (Karl Horky)
50f03a1 docs: Clarify global ignores in config migration guide (#19032) (Milos Djermanovic)

37c9177 build: update @wdio/* dependencies (#19068) (Francesco Trotta)
35a8858 build: exclude flawed dendency versions (#19065) (Francesco Trotta)

Chores

f36cb16 chore: upgrade @eslint/js@9.14.0 (#19086) (Milos Djermanovic)
28be447 chore: package.json update for @eslint/js release (Jenkins)
f48a2a0 test: add no-invalid-regexp tests with RegExp Modifiers (#19075) (Milos Djermanovic)
425202e perf: Fix caching in config loaders (#19042) (Milos Djermanovic)
3d44b3c ci: run tests in Node.js 23 (#19055) (Francesco Trotta)
7259627 test: ensure tmp directory cleanup in check-emfile-handling.js (#19036) (Livia Medeiros)

ESLint v9.13.0 released

2024-10-18T00:00:00Z

Highlights

The predefined array of config objects used by ESLint can be now accessed programmatically as ESLint.defaultConfig.
To speed up loading, the ESLint CLI will automatically enable V8’s code cache in newer versions of Node.js.
Custom languages can now provide their default options with the defaultLanguageOptions property. See the documentation about the Language object.

Features

381c32b feat: Allow languages to provide defaultLanguageOptions (#19003) (Milos Djermanovic)
bf723bd feat: Improve eslintrc warning message (#19023) (Milos Djermanovic)
1def4cd feat: drop support for jiti v1.21 (#18996) (Francesco Trotta)
f879be2 feat: export ESLint.defaultConfig (#18983) (Nitin Kumar)

Bug Fixes

78836d4 fix: update the complexity rule type (#19027) (Nitin Kumar)
064c8b6 fix: update rule types (#18925) (Nitin Kumar)

Documentation

abdbfa8 docs: mark LintMessage#nodeType as deprecated (#19019) (Nitin Kumar)
19e68d3 docs: update deprecated rules type definitions (#19018) (Nitin Kumar)
7dd402d docs: Update examples of passing multiple values to a CLI option (#19006) (Milos Djermanovic)
5dcbc51 docs: Add example with side-effect imports to no-restricted-imports (#18997) (Milos Djermanovic)
1ee87ca docs: Update README (GitHub Actions Bot)
2c3dbdc docs: Use prerendered sponsors for README (#18988) (Milos Djermanovic)

Chores

68d2d9d chore: upgrade to @eslint/js@9.13.0 and @eslint/core@^0.7.0 (#19034) (Francesco Trotta)
2211f0a chore: package.json update for @eslint/js release (Jenkins)
c7abaef perf: using Node.js compile cache (#19012) (唯然)
1d7c077 chore: add pkg.type “commonjs” (#19011) (唯然)
468e3bd test: fix ESLint tests (#19021) (Francesco Trotta)
ed4635f ci: upgrade knip@5.32.0 (#18992) (Milos Djermanovic)
efad767 chore: remove unused ignore dependency (#18993) (Amaresh S M)

no-unused-binary-expressions: From code review nit to ecosystem improvements

2024-10-08T00:00:00Z

Four years ago, while doing a code review at work, I was surprised that Flow had not warned about an unnecessary null check. Last month, TypeScript 5.6 released with validation rules that disallows useless nullish and truthy checks which uncovered nearly 100 existing bugs in the top 800 TypeScript repos on GitHub.

The two events are connected because that moment in code review four years ago led me to write the no-constant-binary-expressions rule which catches a wide variety of bugs. Examples include:

// Expecting empty objects to be falsy
const foo = { ...config } || {};

// Confusing precedence of !
const foo1 = !x == null;

// Confusing ?? or || precedence
const foo2 = x === y ?? true;

The no-constant-binary-expression rule, in turn, helped inspire the newly added TypeScript validations.

Given the protracted timeline and the many intermediate steps, I thought it would be interesting to reflect on how we got here. How did this observation in one code review snowball into a significant positive impact to developers? And how could the snowball continue to grow?

To answer these questions, it helps to review the timeline of events.

Timeline

May 2020: I was reviewing a pull request at work that made a nullable value non-nullable. I noticed that the author had left behind an if condition that handled the now impossible case where the value was null. I started to wonder why Flow hadn’t automatically pointed that out.
May 2020: I posted to an internal group asking the Flow team about it. The answer was that Flow, like TypeScript, is not sound. For example arr[x] is typed as non-nullable but might actually be undefined at runtime. Flow had implemented these checks in the past, but they caused major issues by telling people their null checks were safe to remove when they were not, so they removed the checks. Brad Zacher happened to see the post and chimed in with an observation that a syntactic approach, rather than a type based one, could be safe even if it was less powerful.
August 2020: I implemented the syntactic validation approach as an internal ESLint rule and realized it generalized beyond null checks to all constant comparisons. I ran it in Meta’s mono-repo and found it identified several hundred existing bugs.
October 2020: Brad Zacher suggested I propose it as a new core rule in ESLint. I did, and they liked the idea.
November 2021 - April 2022: I rewrote the rule for open source, which took a surprising amount of effort due to different positions on things like JSX and style.
July 2022: I decided to write a blog post about the new rule. The ESLint team was redoing their site at the time and looking for more blog content, so they asked if I wanted to write the post on the official blog.
November 2023: The blog post made the front page of Hacker News. The post was likely shared by someone who read a tweet I posted sharing that it was going to be enabled by default in eslint:recommended beginning with ESLint v9.0.0.
April 2024: The rule finally ships as enabled by default in ESLint v9.0.0. This change had to wait for a new major version because enabling a new rule in eslint:recommended is a breaking change.
July 2024: The TypeScript team, looking to expand upon the idea of checking for a specific type of constant condition, found the blog post and code. They expanded the set of validations they perform to include most of the checks the ESLint rule performs. They found similar results. 94 real errors in the top 800 TS repos. The success of the ESLint rule gave them confidence to enable the check by default in tsc.
September 2024: TypeScript 5.6 ships with default validations to disallow constant nullish and truthy checks.

Reflections

There were a number of key factors that contributed to this small observation in code review helping spur a meaningful ecosystem wide improvement:

Meta’s internal culture empowered me, a random engineer, to have a direct conversation with members of the Flow team. That conversation happened in a venue where Brad Zacher, an ESLint expert, could happen upon it and chime in.
Meta’s monorepo gave me direct access to a massive codebase which let me easily run early drafts of the rule to assess how impactful the validation would be on a vast amount of real code.
Meta’s culture of autonomy gave me the freedom to take on a side quest of writing this rule despite it not being part of my team’s responsibility.
ESLint’s pluggable architecture empowered me to write my own rule and easily deploy it across the whole company without needing to convince any gate keepers.
The ESLint team’s openness to, and active support of, a new contributor adding a new core rule despite a 2020 policy of only accepting new rules if they relate to new language features.
Active communication about the work initiated by me, and amplified by the ESLint team, in the form of a blog post and tweets. These allowed the TypeScript team to connect the dots between a more specific request they got about disallowing if (/regex/), and the broader idea of detecting constant conditions.
Not being satisfied with just pointing out a useless null check in code review when I suspected that a fundamental solution to that class of problem was possible. Being somewhat obsessive, I wasn’t satisfied until that solution was enabled not just for me, my team, or my company, but for the broader ecosystem.

What’s Next

It’s taken four years for the ripple of Brad’s initial observation on that internal post to reach this point, but I think the ideas here have the potential to resonate even further:

TypeScript and Flow could internally track types which they happen to know are sound, and opportunistically report errors based on that data, allowing checks like this to be performed in many more cases.
Other unsound languages which previously avoided reporting unnecessary checks for the same reason Flow did could use this same approach to catch logic errors.
More broadly, dead code elimination is a well understood area of compiler design with many codified techniques and approaches. However, they are nearly always applied as optimizations in the compiler backend. I suspect many of these same dead code elimination techniques could be brought to the front-end of the compiler and used to detect and report bugs.

Conclusion

This effort spanned multiple years and multiple organizations.

As a motivated individual within Meta, a for-profit company, I was able to spark a conversation which spawned an idea. I was then able to leverage ESLint to validate that idea internally. Once validated, the ESLint project, a not-for-profit organization, brought the idea to a large audience via it’s broad adoption, recommended rule set, and blog. With the idea documented and validated at scale, engineers at Microsoft, another for-profit company, were able to bring the validations to an even larger audience via their open source project TypeScript.

Each organization played a different, but key, role according to its strengths and position. I believe a common thread throughout this process, which enabled this scale of collaboration, was the active socialization of ideas. From asking questions during code review, to asking questions of local experts, to sharing ideas in public blog posts and tweets, each expanding circle of socialization improved the idea and ultimately helped bring it to the broad audience it has reached today.

Thanks to Brad Zacher for his initial key observation and ongoing encouragement, to Nicholas C. Zakas and Milos Djermanovic for significant contributions to the rule during code review, and to Ryan Cavanaugh for bringing these same types of validation to the TypeScript ecosystem.

ESLint v9.12.0 released

2024-10-04T00:00:00Z

Highlights

Experimental configuration file resolution

One of the big changes in ESLint v9.0.0 was the new config system which switched from looking for config files relative to the file being linted to starting the search from the current working directory. While this dramatically decreased the complexity of config file lookup, it also had an unintended side effect: monorepos could no longer include a separate eslint.config.js file in each project directory and then run ESLint with one command from the root. To address this, we’re working on a new configuration file resolution algorithm that more closely mirrors how the eslintrc config system worked.

This new algorithm also starts the search from the file being linted, restoring the monorepo use case and also making it possible to run ESLint from anywhere on any file and get the same results each time. Because this feature is experimental, you’ll need to use the unstable_config_lookup_from_file feature flag, like this:

npx eslint --flag unstable_config_lookup_from_file

For more information on this feature, see Experimental Configuration File Resolution. For more information on using feature flags, see Feature Flags.

Other notable changes

RuleTester now supports custom before and after hooks for test cases.
The complexity rule has a new option variant to support modified cyclomatic complexity.

Features

5a6a053 feat: update to jiti v2 (#18954) (Arya Emami)
17a07fb feat: Hooks for test cases (RuleTester) (#18771) (Anna Bocharova)
2ff0e51 feat: Implement alternate config lookup (#18742) (Nicholas C. Zakas)
2d17453 feat: Implement modified cyclomatic complexity (#18896) (Dmitry Pashkevich)

Bug Fixes

ea380ca fix: Upgrade retry to avoid EMFILE errors (#18986) (Nicholas C. Zakas)
fdd6319 fix: Issues with type definitions (#18940) (Arya Emami)

Documentation

ecbd522 docs: Mention code explorer (#18978) (Nicholas C. Zakas)
7ea4ecc docs: Clarifying the Use of Meta Objects (#18697) (Amaresh S M)
d3e4b2e docs: Clarify how to exclude .js files (#18976) (Milos Djermanovic)
57232ff docs: Mention plugin-kit in language docs (#18973) (Nicholas C. Zakas)
b80ed00 docs: Update README (GitHub Actions Bot)
cb69ab3 docs: Update README (GitHub Actions Bot)
7fb0d95 docs: Update README (GitHub Actions Bot)
493348a docs: Update README (GitHub Actions Bot)
87a582c docs: fix typo in id-match rule (#18944) (Jay)

Chores

555aafd chore: upgrade to @eslint/js@9.12.0 (#18987) (Francesco Trotta)
873ae60 chore: package.json update for @eslint/js release (Jenkins)
d0a5414 refactor: replace strip-ansi with native module (#18982) (Cristopher)
b827029 chore: Enable JSON5 linting (#18979) (Milos Djermanovic)
8f55ca2 chore: Upgrade espree, eslint-visitor-keys, eslint-scope (#18962) (Nicholas C. Zakas)
c1a2725 chore: update dependency mocha to ^10.7.3 (#18945) (Milos Djermanovic)

ESLint now officially supports linting of JSON and Markdown

2024-10-03T00:00:00Z

Back in July we announced our plan for ESLint going forward. Part of that announcement discussed transitioning ESLint to be a more general-purpose linter that is capable of linting any language. A lot of the core functionality of ESLint (finding files, parsing then, reporting problems) is generic, and so we’ve spent the past few months extracting the JavaScript-specific parts of the core. We’re now happy to share that this work has paid by allowing ESLint to now lint both JSON and Markdown!

JSON linting with `@eslint/json`

JSON linting is accomplished using the @eslint/json plugin, which is an officially supported language plugin. The plugin provides parsing for JSON, JSONC (JSON with comments), and JSON5. To use the plugin, install it from npm:

npm install @eslint/json -D

Then update your configuration file:

import json from "@eslint/json";

export default [
    {
        plugins: {
            json,
        },
    },

    // lint JSON files
    {
        files: ["**/*.json"],
        language: "json/json",
        rules: {
            "json/no-duplicate-keys": "error",
        },
    },
];

There are several rules built-in to the plugin, and we’re looking for more suggestions. Have an idea for a rule? Open an issue.

For more information on configuring JSON linting, please check out the README.

Markdown linting with `@eslint/markdown`

Markdown linting is accomplished using the @eslint/markdown plugin, which is the next generation of the eslint-plugin-markdown plugin that only contained a processor. This new officially supported language plugin features parsing and rules for CommonMark and GitHub-Flavored Markdown. To use the plugin, install it from npm:

npm install @eslint/markdown -D

Then update your configuration file:

// eslint.config.js
import markdown from "@eslint/markdown";

export default [
    {
        files: ["**/*.md"],
        plugins: {
            markdown
        },
        language: "markdown/commonmark",
        rules: {
            "markdown/no-html": "error"
        }
    }    
];

Similar to the JSON plugin, there are several rules built-in to the plugin, and we’re looking for more suggestions. Have an idea for a rule? Open an issue.

For more information on configuring Markdown linting, please check out the README.

Creating custom rules and using Code Explorer

Both @eslint/json and @eslint/markdown parse source code into an AST and then traverse the AST to run rules, just like ESLint does with JavaScript. That means you can write custom rules for JSON and Markdown just like you can for JavaScript. The primary difference is in the AST format. JSON uses the Momoa AST while Markdown uses mdast. Because there aren’t a lot of resources out there to help you inspect alternate AST formats, we’re happy to announce the launch of the Code Explorer.

Code Explorer allows you to view and explore the AST of different languages to help in creating custom rules. For JSON and Markdown, you’ll get an expandable view of the AST, while JavaScript allows you to see not just the AST but also the scope and code path information that ESLint generates as it parses your code. Going forward, we’ll continue to update Code Explorer with new languages and capabilities designed to help you create custom rules.

And the best part? Code Explorer is open source, so you can help us make it even better.

Write your own language plugin

ESLint languages are designed in such a way that they can be included in any plugin using a new languages key. The @eslint/json and @eslint/markdown plugins are intended not only to provide JSON and Markdown linting, respectively, but also as examples of how to create your own languages. You can check out the languages documentation for an overview of how you can create your own language.

Conclusion

Linting languages other than JavaScript has been on the ESLint roadmap for a while, so it’s exciting to reach this milestone. Our long-term goal is to ensure that ESLint can lint any kind of file you might use in a web project, whether that be with officially supported language plugins or with community-written plugins. With JavaScript, JSON, and Markdown, we’re already well on our way towards achieving that goal.

As a reminder, ESLint is an independent open source project maintained by a group of volunteers in their spare time. If you enjoy using ESLint, please talk to your company about sponsoring the project.

ESLint v9.11.1 released

2024-09-23T00:00:00Z

Highlights

Several type packages have been added as dependencies to fix compilation errors when ESLint is used in TypeScript code.

Bug Fixes

20fd916 fix: add @eslint/core, @types/estree, & @types/json-schema deps (#18938) (Nitin Kumar)
2738322 fix: add missing types for require-atomic-updates rule (#18937) (Kristóf Poduszló)
d71ff30 fix: add missing types for object-shorthand rule (#18935) (Kristóf Poduszló)
561cadc fix: add missing types for no-unsafe-negation rule (#18932) (Kristóf Poduszló)
8843656 fix: add missing types for no-underscore-dangle rule (#18931) (Kristóf Poduszló)
92cde5c fix: add missing types for no-shadow rule (#18930) (Kristóf Poduszló)
b3cbe11 fix: add missing types for no-sequences rule (#18929) (Kristóf Poduszló)
976f77f fix: add missing types for no-unused-expressions rule (#18933) (Kristóf Poduszló)

Documentation

3eff709 docs: replace deprecated Linter.FlatConfig type with Linter.Config (#18941) (Carlos Meira)

Chores

df4a859 chore: upgrade @eslint/js@9.11.1 (#18943) (Milos Djermanovic)
36d8095 chore: package.json update for @eslint/js release (Jenkins)

ESLint v9.11.0 released

2024-09-20T00:00:00Z

Highlights

The no-useless-constructor rule now provides suggestions for some of the problems reported by this rule.

Features

ec30c73 feat: add “eslint/universal” to export Linter (#18883) (唯然)
c591da6 feat: Add language to types (#18917) (Nicholas C. Zakas)
492eb8f feat: limit the name given to ImportSpecifier in id-length (#18861) (Tanuj Kanti)
19c6856 feat: Add no-useless-constructor suggestion (#18799) (Jordan Thomson)
a48f8c2 feat: add type FormatterFunction, update LoadedFormatter (#18872) (Francesco Trotta)

Bug Fixes

5e5f39b fix: add missing types for no-restricted-exports rule (#18914) (Kristóf Poduszló)
8f630eb fix: add missing types for no-param-reassign options (#18906) (Kristóf Poduszló)
d715781 fix: add missing types for no-extra-boolean-cast options (#18902) (Kristóf Poduszló)
2de5742 fix: add missing types for no-misleading-character-class options (#18905) (Kristóf Poduszló)
c153084 fix: add missing types for no-implicit-coercion options (#18903) (Kristóf Poduszló)
fa11b2e fix: add missing types for no-empty-function options (#18901) (Kristóf Poduszló)
a0deed1 fix: add missing types for camelcase options (#18897) (Kristóf Poduszló)

Documentation

e4e5709 docs: correct prefer-object-has-own type definition comment (#18924) (Nitin Kumar)
91cbd18 docs: add unicode abbreviations in no-irregular-whitespace rule (#18894) (Alix Royere)
59cfc0f docs: clarify resultsMeta in LoadedFormatter type (#18881) (Milos Djermanovic)
adcc50d docs: Update README (GitHub Actions Bot)
4edac1a docs: Update README (GitHub Actions Bot)

959d360 build: Support updates to previous major versions (#18871) (Milos Djermanovic)

Chores

ca21a64 chore: upgrade @eslint/js@9.11.0 (#18927) (Milos Djermanovic)
a10f90a chore: package.json update for @eslint/js release (Jenkins)
e4e02cc refactor: Extract processor logic into ProcessorService (#18818) (Nicholas C. Zakas)
6d4484d chore: updates for v8.57.1 release (Jenkins)
71f37c5 refactor: use optional chaining when validating config rules (#18893) (lucasrmendonca)
2c2805f chore: Add PR note to all templates (#18892) (Nicholas C. Zakas)
7b852ce refactor: use Directive class from @eslint/plugin-kit (#18884) (Milos Djermanovic)
d594ddd chore: update dependency @eslint/core to ^0.6.0 (#18863) (renovate[bot])
78b2421 chore: Update change.yml (#18882) (Nicholas C. Zakas)
a416f0a chore: enable $ExpectType comments in .ts files (#18869) (Francesco Trotta)

ESLint v8.57.1 released

2024-09-16T00:00:00Z

Highlights

Notable bug fixes related to the new config system (eslint.config.js):

Config name property can now also be used with global ignores.
--no-ignore no longer applies to non-global ignores.
The FlatESLint#lintText() method will now respect the fixTypes option when it is specified.

This version also improves configuration error messages by including the name property (if specified on the config object that caused the error), or index in case of non-object elements in the config array.

Bug Fixes

a19072f fix: add logic to handle fixTypes in the lintText() method (#18900) (Francesco Trotta)
04c7188 fix: Don’t lint same file multiple times (#18899) (Francesco Trotta)
87ec3c4 fix: do not throw when defining a global named __defineSetter__ (#18898) (Francesco Trotta)
60a1267 fix: Provide helpful error message for nullish configs (#18889) (Milos Djermanovic)
a0dea8e fix: allow name in global ignores, fix --no-ignore for non-global (#18875) (Milos Djermanovic)
3836bb4 fix: do not crash on error in fs.walk filter (#18886) (Milos Djermanovic)
2dec349 fix: skip processor code blocks that match only universal patterns (#18880) (Milos Djermanovic)

Documentation

6a5add4 docs: v8.x Add EOL banner (#18744) (Amaresh S M)
b034575 docs: v8.x add version support page to the dropdown (#18731) (Amaresh S M)
760ef7d docs: v8.x add version support page in the side navbar (#18740) (Amaresh S M)
428b7ea docs: Add Powered by Algolia label to the search (#18658) (Amaresh S M)
c68c07f docs: version selectors synchronization (#18265) (Milos Djermanovic)

35d366a build: Support updates to previous major versions (#18870) (Milos Djermanovic)

Chores

140ec45 chore: upgrade @eslint/js@8.57.1 (#18913) (Milos Djermanovic)
bcdfc04 chore: package.json update for @eslint/js release (Jenkins)
3f6ce8d chore: pin vite-plugin-commonjs@0.10.1 (#18910) (Milos Djermanovic)
9f07549 chore: ignore /docs/v8.x in link checker (#18660) (Milos Djermanovic)

Version support policy and ESLint v8.x end of life

2024-09-10T00:00:00Z

For ESLint’s entire 11 year existence, we’ve only maintained one major release line at a time. This was both for practical reasons (limited team bandwidth) and technical reasons (our infrastructure was built to assume just one branch). Unfortunately, we haven’t been good at communicating our version support policy, which has led to confusion and frustration when we do a major release.

Adopting a formal version support policy

The Technical Steering Committee has adopted a formal version support policy that explains our approach to supporting major release lines. In general, a major release line may be in one of the following statuses:

Current - Receives active maintenance and development from the ESLint team. A release line is considered current when prerelease work begins.
Maintenance - Receives critical bug fixes, including security issues, and compatibility fixes to ensure interoperability between major release lines. There is no backporting of other fixes or features from the current release line. A release line falls into maintenance status once work begins on the next major release and stays there until six months after the general availability of the current release line.
End of Life (EOL) - When a release line falls out of maintenance mode it receives no further updates from the ESLint team.

Read the full version support policy for more details.

Commercial support from HeroDevs after EOL

Because we realize not everyone can upgrade to a new major release within six months, we’ve partnered with HeroDevs to provide commercial support for EOL release lines. HeroDevs provides drop-in replacements for EOL ESLint packages that keeps your experience seamless.

Additionally, HeroDevs provides never-ending support for these drop-in replacements, meaning that they’ll continue to receive critical security fixes.

ESLint v8.x end of life is October 5, 2024

Following our policy, that puts the end of life for ESLint v8.x on October 5, 2024. After that point, the ESLint team will no longer make changes or publish releases in the v8.x release line. If you need support for v8.x after EOL, please contact HeroDevs.

Conclusion

We hope by adopting a formal version support policy that we’re eliminating the confusion we’ve traditionally had around major releases. We tried to balance the needs of our users with the limitations the team has around availability. ESLint is maintained by a team of volunteers who work in their spare time, and maintaining multiple release lines on our own for an extended period of time is just not possible. That said, we recognize that users need some time to upgrade, and we want to make that as smooth as possible.

By partnering with HeroDevs, we also hope that we’ve made it easier for those who need to stay on an EOL version to get the support that they need.

We’re grateful for the feedback from the community around the v9.0.0 release, and for the help of our friends at HeroDevs who provided guidance around creating our version support policy.

ESLint v9.10.0 released

2024-09-06T00:00:00Z

Highlights

Types now included

We’ve been receiving complaints about the @types/eslint package not being updated after the v9 release. While we did do an initial update to the package for v9, it quickly became apparent that regular updates to that package could not be accomplished in a timely manner. Ultimately, we decided that the only way for us to provide the type of experience we want for ESLint is to take complete ownership of the type definitions.

As a result, beginning with this release, the eslint package now publishes its own types. To start, we’ve copied the type definitions from @types/eslint in order to provide a smooth transition. (There was one bug in the types that we fixed, but otherwise it’s the same type definitions.) Going forward, we’ll continue to iterate and improve the type definitions as part of our regular release cycle.

We’re grateful to everyone who contributed types to the @types/eslint package at a time when we weren’t ready to take that work on.

Other notable changes

The require-unicode-regexp rule can now enforce usage of the v flag with regular expressions. Check out the new option requireFlag.
This release also fixes problems found in the id-length and no-invalid-regexp rules.

Features

301b90d feat: Add types (#18854) (Nicholas C. Zakas)
bcf0df5 feat: limit namespace import identifier in id-length rule (#18849) (ChaedongIm)
45c18e1 feat: add requireFlag option to require-unicode-regexp rule (#18836) (Brett Zamir)
183b459 feat: add error message for duplicate flags in no-invalid-regexp (#18837) (Tanuj Kanti)
c69b406 feat: report duplicate allowed flags in no-invalid-regexp (#18754) (Tanuj Kanti)

Documentation

bee0e7a docs: update README (#18865) (Milos Djermanovic)
5d80b59 docs: specify that ruleId can be null in custom formatter docs (#18857) (Milos Djermanovic)
156b1c3 docs: Update README (GitHub Actions Bot)
f6fdef9 docs: Update README (GitHub Actions Bot)
a20c870 docs: Update README (GitHub Actions Bot)
90e699b docs: Update README (GitHub Actions Bot)

Chores

24c3ff7 chore: upgrade to @eslint/js@9.10.0 (#18866) (Francesco Trotta)
1ebdde1 chore: package.json update for @eslint/js release (Jenkins)
e8fc5bd chore: update dependency @eslint/core to ^0.5.0 (#18848) (renovate[bot])
343f992 refactor: don’t use node.value when removing unused directives (#18835) (Milos Djermanovic)
3db18b0 refactor: Extract FileContext into class (#18831) (Nicholas C. Zakas)
931d650 refactor: Use @eslint/plugin-kit (#18822) (Nicholas C. Zakas)
ed5cf0c chore: update dependency @eslint/json to ^0.4.0 (#18829) (Milos Djermanovic)
d1f0831 chore: added missing ids (#18817) (Strek)
ec92813 refactor: Config class (#18763) (Nicholas C. Zakas)

Trunk becomes ESLint gold sponsor

2024-09-04T00:00:00Z

We are happy to share that Trunk has become an ESLint gold sponsor, donating $1,000 each month for the ongoing maintenance and development of ESLint! Trunk is a suite of tools aimed at making developers more effective, including Code Quality that integrates ESLint directly, and Merge Queue, with more tools in development.

Here’s what the folks at Trunk had to say about ESLint:

"ESLint is a core part of the Trunk Code Quality plugin ecosystem. It’s the most popular linter plugin and is enabled by default on all JS and TS projects running Code Quality. ESLint also runs on all of Trunk’s Typescript source code.

Code Quality, as a metalinter, is built on top of great open-source linters like ESLint. Sponsoring ESLint and helping ESLint leverage Trunk Code Quality on their open-source repo is an excellent way for us to give back."

– David Apirian, Trunk Founder

The ESLint team and the Trunk team worked together over the past few months to integrate Code Quality into the ESLint repository, where it now runs ESLint on itself, as well as several other linters. Throughout this process, we’ve worked to ensure that ESLint and Code Quality work well together across a variety of scenarios.

ESLint is grateful for the support of the Trunk team as they used ESLint in their commercial products. Donations from companies like Trunk allow ESLint to pay contributors for ongoing maintenance and development.

ESLint v9.9.1 released

2024-08-23T00:00:00Z

Highlights

The lintText() method will now respect the fixTypes option when it is specified.

Bug Fixes

9bde90c fix: add logic to handle fixTypes in lintText() (#18736) (Amaresh S M)

Documentation

4840930 docs: Update README with version support and clean up content (#18804) (Nicholas C. Zakas)
f61f40d docs: Update globals examples (#18805) (Nicholas C. Zakas)
241fcea docs: Use and define languages (#18795) (Nicholas C. Zakas)
5dbdd63 docs: eslint-plugin-markdown -> @eslint/markdown (#18797) (Nicholas C. Zakas)
c6c8ddd docs: update links to eslint-visitor-keys repo (#18796) (Francesco Trotta)
f981d05 docs: Update README (GitHub Actions Bot)
b516974 docs: update links to eslint/js repo (#18781) (Francesco Trotta)
fb7a3f5 docs: update note for package managers (#18779) (Jay)

Chores

b0c34d0 chore: upgrade to @eslint/js@9.9.1 (#18809) (Francesco Trotta)
cd5a0da chore: package.json update for @eslint/js release (Jenkins)
e112642 refactor: Extract parsing logic from Linter (#18790) (Nicholas C. Zakas)
0f68a85 chore: use eslint-plugin-yml on yaml files only (#18801) (Milos Djermanovic)
f8d1b3c chore: update dependencies for browser tests (#18794) (Christian Bromann)
aed2624 chore: update dependency @eslint/config-array to ^0.18.0 (#18788) (renovate[bot])
5c29128 chore: update dependency @eslint/core to ^0.4.0 (#18789) (renovate[bot])
5d66fb2 chore: migrate linting workflow to use trunk check meta-linter (#18643) (Chris Clearwater)
bf96855 chore: add ids to github issue templates (#18775) (Strek)

ESLint v9.9.0 released

2024-08-09T00:00:00Z

Highlights

Here are some of the key changes in this release.

Experimental TypeScript configuration files

Arya Emami landed experimental support for TypeScript configuration files. Specifically, you can now use eslint.config.ts, eslint.config.mts, and eslint.config.cts files as your configuration files. Because this feature is experimental, you’ll need to use the unstable_ts_config feature flag:

npx eslint --flag unstable_ts_config

For Node.js, you’ll need to manually install jiti, which provides the TypeScript-to-JavaScript functionality; for Deno and Bun, no additional dependency is necessary. (When TypeScript type stripping lands as stable in Node.js, you also won’t need an additional dependency in Node.js)

For more information on this feature, see TypeScript Configuration Files. For more information on using feature flags, see Feature Flags.

Other notable changes

The require-await rule now suggests to remove possibly unnecessary usages of the async keyword.

Features

41d0206 feat: Add support for TS config files (#18134) (Arya Emami)
3a4eaf9 feat: add suggestion to require-await to remove async keyword (#18716) (Dave)

Documentation

9fe068c docs: how to author plugins with configs that extend other configs (#18753) (Alec Gibson)
48117b2 docs: add version support page in the side navbar (#18738) (Amaresh S M)
fec2951 docs: add version support page to the dropdown (#18730) (Amaresh S M)
38a0661 docs: Fix typo (#18735) (Zaina Al Habash)
3c32a9e docs: Update yarn command for creating ESLint config (#18739) (Temitope Ogunleye)
f9ac978 docs: Update README (GitHub Actions Bot)

Chores

461b2c3 chore: upgrade to @eslint/js@9.9.0 (#18765) (Francesco Trotta)
59dba1b chore: package.json update for @eslint/js release (Jenkins)
fea8563 chore: update dependency @eslint/core to ^0.3.0 (#18724) (renovate[bot])
aac191e chore: update dependency @eslint/json to ^0.3.0 (#18760) (renovate[bot])
b97fa05 chore: update wdio dependencies for more stable tests (#18759) (Christian Bromann)

ESLint v9.8.0 released

2024-07-26T00:00:00Z

Highlights

Ignoring the directory where ESLint runs is no longer possible. Previously, a global ignores pattern like "/" would ignore the entire base directory.
The feature flags specification has been updated to forbid the usage of inactive flags.

Features

13d0bd3 feat: Add and use SourceCode#getLoc/getRange (#18703) (Nicholas C. Zakas)

Bug Fixes

ab0ff27 fix: Throw error when invalid flags passed (#18705) (Nicholas C. Zakas)
70dc803 fix: basePath directory can never be ignored (#18711) (Milos Djermanovic)

Documentation

282df1a docs: Add system theme option (#18617) (Amaresh S M)
53b1ff0 docs: Debug config docs (#18698) (Nicholas C. Zakas)
a7016a5 docs: fix search input stylings (#18682) (Amaresh S M)

4514424 build: Enable JSON linting (#18681) (Nicholas C. Zakas)

Chores

deee448 chore: upgrade to @eslint/js@9.8.0 (#18720) (Francesco Trotta)
4aaf2b3 chore: package.json update for @eslint/js release (Jenkins)
8e1a627 chore: update dependency @eslint/core to ^0.2.0 (#18700) (renovate[bot])

ESLint v9.7.0 released

2024-07-12T00:00:00Z

Highlights

ESLint v9.7.0 supports ECMAScript 2025 duplicate capturing groups in regular expressions in its core rules.
The no-restricted-imports rule has a new option regex to specify modules using a regular expression pattern.

Features

7bd9839 feat: add support for es2025 duplicate named capturing groups (#18630) (Yosuke Ota)
1381394 feat: add regex option in no-restricted-imports (#18622) (Nitin Kumar)

Bug Fixes

14e9f81 fix: destructuring in catch clause in no-unused-vars (#18636) (Francesco Trotta)

Documentation

9f416db docs: Add Powered by Algolia label to the search. (#18633) (Amaresh S M)
c8d26cb docs: Open JS Foundation -> OpenJS Foundation (#18649) (Milos Djermanovic)
6e79ac7 docs: loadESLint does not support option cwd (#18641) (Francesco Trotta)

Chores

793b718 chore: upgrade @eslint/js@9.7.0 (#18680) (Francesco Trotta)
7ed6f9a chore: package.json update for @eslint/js release (Jenkins)
7bcda76 refactor: Add type references (#18652) (Nicholas C. Zakas)
51bf57c chore: add tech sponsors through actions (#18624) (Strek)
6320732 refactor: don’t use parent property in NodeEventGenerator (#18653) (Milos Djermanovic)
9e6d640 refactor: move “Parsing error” prefix adding to Linter (#18650) (Milos Djermanovic)

What's coming next for ESLint

2024-07-05T00:00:00Z

When we released ESLint v9.0.0 in April, it was the first major release in 30 months and formally introduced the new configuration system. ESLint v9.0.0 also made some rule API changes to prepare the core for what’s coming next. After the release, we spent a lot of time creating compatibility utilities, a configuration migration tool, and a rule API transform utility to help the ecosystem move to ESLint v9.0.0. All of that work was necessary for us to move on to the next significant changes coming to ESLint.

Language plugins

Two years ago, the TSC decided that it was time to open up ESLint to make it possible to lint languages other than JavaScript. Practically speaking, there are a lot of things that the ESLint core does that are not specific to JavaScript: the finding and reading of files, the loading of file-specific configuration, collecting rule violations, outputting results to the console, and so on. Further, we kept finding plugins that were linting other languages (like GraphQL and HTML) from within ESLint, passing a different AST through the same logic that JavaScript was using. That’s inefficient and error-prone, and there had to be a better way.

In 2023, the language plugins RFC was formally approved. In order to implement this RFC, however, we needed to officially ship the new configuration and make some rule API changes. The rule API changes, in particular, were necessary to separate what the ESLint core was doing and what a language plugin would provide to custom rules. Once those two changes were available, we started the laborious task of refactoring the ESLint core to extract the JavaScript-specific parts from the language-agnostic parts.

Here’s what to expect going forward (with no specific timetable as everything is dependent upon contributor availability):

@eslint/js - We will slowly move all of the JavaScript-related functionality into the @eslint/js package, including rules and documentation. We will reuse the existing Espree repo and convert it into a monorepo containing Espree, eslint-scope, eslint-visitor-keys, and all of the core JavaScript rules. This will allow us to deal with everything JavaScript-related in a single repo.
@eslint/json - Our first language plugin will allow ESLint to lint JSON files natively. This plugin will contain the parsing logic and all of the related rules and documentation. Similar to @eslint/js, this will allow us to have a single repo to focus on JSON linting, further moving any language-specific functionality away from the core.
@eslint/markdown - eslint-plugin-markdown will be renamed to @eslint/markdown to better align with the other packages. We’ll add the ability to lint Markdown and Markdown-specific rules.

The current plan is to have these three official ESLint language plugins with the hopes that they serve as examples for the ecosystem to develop more language plugins.

With language-specific functionality extracted into separate repositories, that leaves us with the task of rewriting the core completely.

Core rewrite

The architecture of the code in the ESLint repository hasn’t changed considerably since ESLint was first created 11 years ago. As a result, there is a lot of technical debt that has accumulated and prevents us from making some of the changes we’d like to make. Some of the problems we currently face:

Synchronous core logic. The Linter class is completely synchronous, meaning we can’t support asynchronous rules or asynchronous parsing, two feature requests we receive frequently. We’d need to either add a second class that works asynchronously or add alternate methods to Linter that work asynchronously. Both options looked like significant work, effectively rewriting huge parts of the core.
Limited API. The public API is limited because ESLint, at the start, was never intended to be used as an API. The initial linter object was meant only to enable a browser demo. It was later replaced by the Linter class, and even later, an ESLint class to fully mimic the command line interface. When we want to expose new functionality, it needs to exist in one of these two similar-sounding APIs, and unfortunately, the main decision point is whether or not the API needs to be available in the browser. If so, then it needs to be in Linter, otherwise it needs to be in ESLint. This is both confusing and not sustainable in the long term.
Lack of type checking. We’ve had the desire to add type checking into the repository to help catch potential problems, but attempts to do this in the past required a lot of work and coordination. Eventually, we came to the conclusion that it wasn’t worth the effort.
Stuck in CommonJS. Similar to the type checking situation, while there is a desire to convert the codebase into ESM, the amount of work it would take to do so is prohibitive. We’d spend a lot of time on the conversion just to end up with an equivalent feature set.

After thinking through the options of continually to incrementally change the existing core or starting from scratch, we decided that it was time to start from scratch. While we firmly believe that a complete rewrite represents a significant risk, after 11 years, we can honestly say that we got the most out of the initial architecture.

Going forward, here’s what you can expect:

A new repository. The eslint/rewrite repository is the new home for our language-agnostic work. It’s a monorepo where we’ll manage all of the packages that directly relate to the core in some way.
Modern packages. Every package in eslint/rewrite will be up to modern standards, publishing ESM entrypoints along with type definitions. When possible, we’ll also publish CommonJS entrypoints. All packages are published with provenance to both npm and JSR (when applicable).
A runtime-agnostic core. The @eslint/core package will contain a runtime-agnostic API for ESLint along with type definitions for the core. We will build this package up slowly over time as we design the new API, extracting pieces of functionality out of the eslint package. With more JavaScript runtimes emerging each year, we feel that a runtime-agnostic core is becoming more important.
A composable API. Instead of bundling all functionality into one or two classes, the new API will be composable, with many purpose-built classes designed to be used together. Class will follow the single-responsibility principle, making it easier to make changes and customize ESLint inside of integrations.
A new CLI. We’ll be rewriting the CLI from scratch in the @eslint/node package. We’ll start with the most common use cases and reevaluate each flag to make sure it still makes sense for a language-agnostic core. Using a different package name allows us to experiment with the new CLI without disrupting the use of the eslint package. This package will also export additional Node.js-specific APIs.
Parallel development. We will continue to maintain eslint and the rewrite in parallel so that we aren’t sacrificing the existing package for something completely new. The goal is for the eslint package to slowly become smaller and make use of the APIs contained in @eslint/core so we are limiting duplication as much as possible.

Conclusion

We are very excited for this future direction of ESLint as we think this represents the next logical step in ESLint’s evolution. Turning ESLint into a language-agnostic linter that anyone can write plugins for will simplify development by reducing the number of linting tools and editor extensions any one project needs. Further, rewriting our core into a more composable API allows easier and more customizable integrations, along with owning our own type definitions to ensure compatibility with the APIs.

ESLint has made it through 11 years with its current architecture, and we hope that these changes will get us through the next 11 years.

ESLint v9.6.0 released

2024-06-28T00:00:00Z

Highlights

ESLint’s default parser espree now supports RegExp duplicate named capturing groups ES2025 syntax when languageOptions.ecmaVersion is set to 2025 or "latest" (default). Please note that the core rules have not yet been updated to support this syntax.
Backslash (\) can now be used as an escape character in files and ignores patterns, regardless of the operating system. Note that only forward slash (/) is interpreted as a path separator in files and ignores patterns, regardless of the operating system.
The messages reported by the no-unused-vars rule have been improved to include configured ignore patterns for different kinds of variables.

Features

e2b16e2 feat: Implement feature flags (#18516) (Nicholas C. Zakas)
8824aa1 feat: add ecmaVersion: 2025, parsing duplicate named capturing groups (#18596) (Milos Djermanovic)

Bug Fixes

1613e2e fix: Allow escaping characters in config patterns on Windows (#18628) (Milos Djermanovic)
21d3766 fix: no-unused-vars include caught errors pattern in report message (#18609) (Kirk Waiblinger)
d7a7736 fix: improve no-unused-vars message on unused caught errors (#18608) (Kirk Waiblinger)
f9e95d2 fix: correct locations of invalid /* eslint */ comments (#18593) (Milos Djermanovic)

Documentation

13dbecd docs: Limit search to just docs (#18627) (Nicholas C. Zakas)
375227f docs: Update getting-started.md - add pnpm to init eslint config (#18599) (Kostiantyn Ochenash)
44915bb docs: Update README (GitHub Actions Bot)
d50db7b docs: Update vscode-eslint info (#18595) (Nicholas C. Zakas)

Chores

b15ee30 chore: upgrade @eslint/js@9.6.0 (#18632) (Milos Djermanovic)
d655503 chore: package.json update for @eslint/js release (Jenkins)
7c78ad9 refactor: Use language.visitorKeys and check for non-JS SourceCode (#18625) (Nicholas C. Zakas)
69ff64e refactor: Return value of applyInlineConfig() (#18623) (Nicholas C. Zakas)
d2d06f7 refactor: use / separator when adjusting ignorePatterns on Windows (#18613) (Milos Djermanovic)
6421973 refactor: fix disable directives for languages with 0-based lines (#18605) (Milos Djermanovic)
0a13539 refactor: Allow optional methods for languages (#18604) (Nicholas C. Zakas)
c7ddee0 chore: make internal-rules not being a package (#18601) (Milos Djermanovic)
3379164 chore: remove .eslintrc.js (#18011) (唯然)
d0c3a32 chore: update knip (with webdriver-io plugin) (#18594) (Lars Kappert)

ESLint v9.5.0 released

2024-06-14T00:00:00Z

Highlights

The @eslint/compat package now provides utility for including .gitignore files or any other files with gitignore-style patterns in your eslint.config.js file.
Messages about ignored files have been improved to distinguish between files that are ignored because of a matching ignore pattern, files that are ignored because no matching configuration is supplied, and files that are ignored because they are located outside of the base path.
The no-sparse-arrays rule now reports precise locations of holes in array literals.

Features

b2d256c feat: no-sparse-arrays report on “comma” instead of the whole array (#18579) (fisker Cheung)

Bug Fixes

6880286 fix: treat * as a universal pattern (#18586) (Milos Djermanovic)
7fbe211 fix: message template for all files ignored (#18564) (Milos Djermanovic)
469cb36 fix: Don’t lint the same file multiple times (#18552) (Milos Djermanovic)
5cff638 fix: improve message for ignored files without a matching config (#18404) (Francesco Trotta)

Documentation

455f7fd docs: add section about including .gitignore files (#18590) (Milos Djermanovic)
721eafe docs: update info about universal files patterns (#18587) (Francesco Trotta)
8127127 docs: Update README (GitHub Actions Bot)
55c2a66 docs: Update README (GitHub Actions Bot)
eb76282 docs: Update README (GitHub Actions Bot)
ff6e96e docs: baseConfig and overrideConfig can be arrays (#18571) (Milos Djermanovic)
d2d83e0 docs: Add mention of eslint-transforms to v9 migration guide (#18566) (Nicholas C. Zakas)
9ce6832 docs: add callout box for unintuitive behavior (#18567) (Ben McCann)
b8db99c docs: Add VS Code info to config migration guide (#18555) (Nicholas C. Zakas)
518a35c docs: Mention config migrator (#18561) (Nicholas C. Zakas)
eb440fc docs: specifying files with arbitrary or no extension (#18539) (Francesco Trotta)
38c159e docs: Provide example of reading package.json for plugins meta (#18530) (Nicholas C. Zakas)
d16a659 docs: add link to migration guide for --ext CLI option (#18537) (Milos Djermanovic)
73408de docs: add link to configuration file docs before examples (#18535) (Milos Djermanovic)

Chores

f588160 chore: upgrade @eslint/js@9.5.0 (#18591) (Milos Djermanovic)
5890841 chore: package.json update for @eslint/js release (Jenkins)
e9f4ccd chore: remove unused eslint-disable directive (#18589) (Milos Djermanovic)
4b23ffd refactor: Move JS parsing logic into JS language (#18448) (Nicholas C. Zakas)
1495b93 chore: update WebdriverIO packages (#18558) (Christian Bromann)
cea7ede chore: add website donate link instead of opencollective (#18582) (Strek)
ec94880 chore: package.json update for eslint-config-eslint release (Jenkins)
6912586 chore: extract formatting rules into separate config (#18560) (Milos Djermanovic)
9738f7e ci: fix CLI flags for c8, raise thresholds (#18554) (Francesco Trotta)
c6de7bb chore: update dependency markdownlint-cli to ^0.41.0 (#18538) (renovate[bot])
2c8fd34 ci: pin @wdio/browser-runner v8.36.0 (#18540) (唯然)

ESLint v9.4.0 released

2024-05-31T00:00:00Z

Highlights

The no-loop-func rule no longer reports on IIFE’s.
The --inspect-config CLI flag will now launch the latest version of the ESLint Config Inspector.
The no-constructor-return rule now allows return statements without a value anywhere in a constructor.

Features

89a4a0a feat: ignore IIFE’s in the no-loop-func rule (#17528) (Nitin Kumar)

Bug Fixes

f6534d1 fix: skip processor code blocks that match only universal patterns (#18507) (Milos Djermanovic)
7226ebd fix: allow implicit undefined return in no-constructor-return (#18515) (Ali Rezvani)
389744b fix: use @eslint/config-inspector@latest (#18483) (唯然)
70118a5 fix: func-style false positive with arrow functions and super (#18473) (Milos Djermanovic)

Documentation

d7ab6f5 docs: update theme when when prefers-color-scheme changes (#18510) (Nitin Kumar)
525fdff docs: fix components files (#18519) (Tanuj Kanti)
80747d2 docs: refactor prefer-destructuring rule (#18472) (Tanuj Kanti)
f06e0b5 docs: clarify func-style (#18477) (Cameron Steffen)

Chores

010dd2e chore: upgrade to @eslint/js@9.4.0 (#18534) (Francesco Trotta)
5e1b5dc chore: package.json update for @eslint/js release (Jenkins)
594145f refactor: switch to @eslint/config-array (#18527) (Francesco Trotta)

Introducing the ESLint Configuration Migrator

2024-05-31T00:00:00Z

We’ve heard you: One of the biggest reasons ESLint users haven’t upgraded to ESLint v9.x is migrating a configuration file seems difficult and complicated. Some plugins support flat config and the ESLint v9.x rule APIs and some don’t. Sometimes you need to use FlatCompat and sometimes you need to use the compatibility utilities. While we cover as much as we can in the migration guide, it can take time to walk through your configuration and make the necessary changes.

That’s why we’re excited to announce the release of the ESLint Configuration Migrator. This utility is designed to translate .eslintrc.* files into eslint.config.js files, including:

1-for-1 migration of .eslintrc, .eslintrc.json, .eslintrc.yml, and .eslintrc.yaml files.
Reasonable migration of simple .eslintrc.js, .eslintrc.cjs, and .eslintrc.mjs files. (These will often need edits if you are using variables to build your config).
Automatic inclusion of .eslintignore patterns into your new config file.
Automatic use of FlatCompat when necessary.
Automatic use of the compatibility utilities when necessary.

Important: This version of the utility does not handle anything but the simplest JavaScript configuration file (.eslintrc.js, .eslintrc.cjs, .eslintrc.mjs). It works by evaluating the file and then migrating the calculated configuration. As such, it will not maintain any logic inside of the file. We hope to add this capability in a future version.

Using the configuration migrator

You can use the configuration migrator directly from npm without installing it via npx or similar commands. Pass the location of the .eslintrc.* file to convert, like this:

npx @eslint/migrate-config .eslintrc.json
# or
yarn dlx @eslint/migrate-config .eslintrc.json
# or
pnpm dlx @eslint/migrate-config .eslintrc.json
# or
bunx @eslint/migrate-config .eslintrc.json

By default, this command will output a eslint.config.mjs file. If you’d like to output a CommonJS file instead, add the --commonjs flag:

npx @eslint/migrate-config .eslintrc.json --commonjs
# or
yarn dlx @eslint/migrate-config .eslintrc.json --commonjs
# or
pnpm dlx @eslint/migrate-config .eslintrc.json --commonjs
# or
bunx @eslint/migrate-config .eslintrc.json --commonjs

Limitations

The goal of the configuration migrator is to reduce the likelihood of running into errors when you use it for the first time, and as a result, it aggressively employs FlatCompat and the compatibility utilities. This means that the generated configuration file may not be optimal and you may be able to simplify it yourself.

After generating a configuration file, you should review the following:

Are there more recent versions of plugins? It’s possible that there’s a newer version of a plugin that fully supports ESLint v9.x on its own and doesn’t require any kind of compatibility work. It’s always best to upgrade to the latest version of the plugins you use.
Do you have .eslintrc.* config files in other directories? The new configuration system doesn’t merge configuration files from ancestor directories. If you are using .eslintrc.* files to override configuration in specific directories, you’ll need to move that configuration into your primary eslint.config.* file.
Were you using the --ext CLI flag? If so, you’ll need to create an entry in your configuration file to match the file extensions you use to pass on the command line.

It’s possible that the generated configuration file won’t work without some modification, but it should get you very close.

Conclusion

When we released ESLint v9.x, we thought providing the configuration migration guide would get most users through the transition to the new configuration system. Unfortunately, we didn’t anticipate all of the challenges that folks would encounter along the way. We hope that the configuration migrator makes this transition a lot easier going forward. Getting every config file to work 100% after migration is impossible due to the various ways that people configure ESLint, but we think that this tool should avoid most tedious translation steps to get you up and running in ESLint v9.x faster.

ESLint v9.3.0 released

2024-05-17T00:00:00Z

Highlights

ESLint v9.3.0 adds new options to some rules:

func-style has the new option overrides.namedExports
no-extra-boolean-cast has the new option enforceForInnerExpressions superseding the deprecated but still recognized enforceForLogicalOperands option
no-misleading-character-class has the new new option allowEscape
no-restricted-exports has the new option restrictedNamedExportsPattern

The built-in rules line-comment-position and multiline-comment-style have been deprecated in favor of third-party replacements.

Features

b32153c feat: add overrides.namedExports to func-style rule (#18444) (Percy Ma)
b67eba4 feat: add restrictedNamedExportsPattern to no-restricted-exports (#18431) (Akul Srivastava)
069aa68 feat: add option allowEscape to no-misleading-character-class rule (#18208) (Francesco Trotta)
05ef92d feat: deprecate multiline-comment-style & line-comment-position (#18435) (唯然)
db0b174 feat: add enforceForInnerExpressions option to no-extra-boolean-cast (#18222) (Kirk Waiblinger)

Bug Fixes

8db0eff fix: Improve config error messages (#18457) (Nicholas C. Zakas)
5c28d9a fix: don’t remove comments between key and value in object-shorthand (#18442) (Kuba Jastrzębski)
39fb0ee fix: object-shorthand loses type parameters when auto-fixing (#18438) (dalaoshu)
37eba48 fix: don’t crash when fs.readFile returns promise from another realm (#18416) (Milos Djermanovic)

Documentation

ceada8c docs: explain how to use “tsc waiting” label (#18466) (Francesco Trotta)
62e686c docs: Add troubleshooting info for plugin compatibility (#18451) (Nicholas C. Zakas)
e17e1c0 docs: Update README (GitHub Actions Bot)
2465a1e docs: Update README (GitHub Actions Bot)
d23574c docs: Clarify usage of no-unreachable with TypeScript (#18445) (benj-dobs)
1db9bae docs: Fix typos (#18443) (Frieder Bluemle)
7065196 docs: Update README (GitHub Actions Bot)
04e7c6e docs: update deprecation notice of no-return-await (#18433) (Tanuj Kanti)
e763512 docs: Link global ignores section in config object property list (#18430) (MaoShizhong)
ac7f718 docs: reflect release of v9 in config migration guide (#18412) (Peter Briggs)
0de0909 docs: fix grammar in configuration file resolution (#18419) (Mike McCready)

Chores

58e2719 chore: update dependencies for v9.3.0 release (#18469) (Francesco Trotta)
b681ecb chore: package.json update for @eslint/js release (Jenkins)
06f1d1c chore: update dependency @humanwhocodes/retry to ^0.3.0 (#18463) (renovate[bot])
a63ed72 refactor: Use node: protocol for built-in Node.js modules (#18434) (Milos Djermanovic)
040700a chore: update dependency markdownlint-cli to ^0.40.0 (#18425) (renovate[bot])
f47847c chore: update actions/stale action to v9 (#18426) (renovate[bot])
c18ad25 chore: update actions/upload-artifact action to v4 (#18427) (renovate[bot])
27e3060 chore: Disable documentation label (#18423) (Nicholas C. Zakas)

Introducing ESLint Compatibility Utilities

2024-05-09T00:00:00Z

The release of ESLint v9.0.0 brought with it the rollout of the new configuration system, but also a series of changes to the rules API. These changes are necessary in order to prepare ESLint for implementing language plugins, which will give ESLint the ability to natively lint languages other than JavaScript. As a result, plugin authors needed to update their rules to work with v9.0.0, and unfortunately, that means some of the plugins you rely on may not have been updated yet. That’s why we’re releasing the compatibility utilities.

How to know if the compatibility utilities will help

These utilities may help if you encounter any of the following errors while running ESLint:

TypeError: context.getScope is not a function
TypeError: context.getAncestors is not a function
TypeError: context.markVariableAsUsed is not a function
TypeError: context.getDeclaredVariables is not a function

These errors mean that the plugin rules have not been updated to the latest ESLint rule API.

Using the compatibility utilities

First, install the @eslint/compat package using npm or any npm-compatible CLI:

npm install @eslint/compat -D
# or
yarn add @eslint/compat -D
# or
pnpm install @eslint/compat -D
# or
bun install @eslint/compat -D

Then, use the fixupPluginRules() function in your eslint.config.js file to wrap the plugin in a compatibility layer:

// eslint.config.js
import { fixupPluginRules } from "@eslint/compat";
import example from "eslint-plugin-example";

export default [
    {
        plugins: {
            example: fixupPluginRules(example)
        }
    },

    // other config
];

After that, the plugin should work as expected.

Fixing an imported configuration

If you are importing a flat-style configuration from another package that references plugins, you can use the fixupConfigRules() function to wrap all of the plugins found, like this:

// eslint.config.js
import { fixupConfigRules } from "@eslint/compat";
import recommended from "eslint-plugin-example/configs/recommended.js";

export default [

    ...fixupConfigRules(recommended)

    // other config
];

The fixupConfigRules() function accepts both a single object and an array of objects to easily update any configuration you’re using.

Using with `FlatCompat`

If you are using FlatCompat from the @eslint/eslintrc package, you may not be able to access each of the plugins that are referenced inside of an eslintrc-style configuration. In that case, you can use the fixupConfigRules() function to wrap all plugins, as in this example:

// eslint.config.js
import { fixupConfigRules } from "@eslint/compat";
import { FlatCompat } from "@eslint/eslintrc";

const flatCompat = new FlatCompat();

export default [

    ...fixupConfigRules(
        flatCompat.extends("my-config")
    )

    // other config
];

While this example shows how to use fixupConfigRules() with the extends() method, any method on FlatCompat works.

Conclusion

One of the benefits of the new configuration system is that it allows us the ability to patch plugins and configs that haven’t yet been updated by their maintainers. We know it can be frustrating to migrate to ESLint v9.0.0 and have your configuration not work, and that’s why we’re committed to providing packages like @eslint/eslintrc and @eslint/compat to help aid the transition.

ESLint v9.2.0 released

2024-05-03T00:00:00Z

Highlights

The no-case-declarations rule now provides suggestions for some of the problems reported by this rule.

Features

8485d76 feat: no-case-declarations add suggestions (#18388) (Josh Goldberg ✨)
a498f35 feat: update Unicode letter detection in capitalized-comments rule (#18375) (Francesco Trotta)

Bug Fixes

eeec413 fix: do not throw when defining a global named __defineSetter__ (#18364) (唯然)

Documentation

0f5df50 docs: Update README (GitHub Actions Bot)
1579ce0 docs: update wording regarding indirect eval (#18394) (Kirk Waiblinger)
f12a02c docs: update to eslint v9 in custom-rule-tutorial (#18383) (唯然)

Chores

b346605 chore: upgrade @eslint/js@9.2.0 (#18413) (Milos Djermanovic)
c4c18e0 chore: package.json update for @eslint/js release (Jenkins)
284722c chore: package.json update for eslint-config-eslint release (Jenkins)
347d44f chore: remove eslintrc export from eslint-config-eslint (#18400) (Milos Djermanovic)
f316e20 ci: run tests in Node.js 22 (#18393) (Francesco Trotta)

ESLint v9.1.1 released

2024-04-22T00:00:00Z

Highlights

Fixed an issue that would sometimes cause an outdated version of @eslint/create-config to be used when running npx eslint --init.

Bug Fixes

a26b402 fix: use @eslint/create-config latest (#18373) (唯然)

ESLint v9.1.0 released

2024-04-19T00:00:00Z

Highlights

This is the first minor release of ESLint following the major release of ESLint v9.0.0 earlier this month.

Intl is now recognized as a built-in global unless languageOptions.ecmaVersion is set to 3 or 5.
The no-constant-condition rule no longer reports while (true) loops as problems by default.
A configuration that contains a non-global ignores pattern list will no longer cause incorrect results when the --no-ignore CLI flag is used, or when the ESLint constructor option ignore is set to false.

Features

03068f1 feat: Provide helpful error message for nullish configs (#18357) (Nicholas C. Zakas)
751b518 feat: replace dependency graphemer with Intl.Segmenter (#18110) (Francesco Trotta)
4d11e56 feat: add name to eslint configs (#18289) (唯然)
1cbe1f6 feat: allow while(true) in no-constant-condition (#18286) (Tanuj Kanti)
0db676f feat: add Intl in es6 globals (#18318) (唯然)

Bug Fixes

8d18958 fix: Remove name from eslint/js packages (#18368) (Nicholas C. Zakas)
594eb0e fix: do not crash on error in fs.walk filter (#18295) (Francesco Trotta)
0d8cf63 fix: EMFILE errors (#18313) (Nicholas C. Zakas)
e1ac0b5 fix: --inspect-config only for flat config and respect -c (#18306) (Nicholas C. Zakas)
09675e1 fix: --no-ignore should not apply to non-global ignores (#18334) (Milos Djermanovic)

Documentation

fb50077 docs: include notes about globals in migration-guide (#18356) (Gabriel Rohden)
71c771f docs: Fix missing accessible name for scroll-to-top link (#18329) (Germán Freixinós)
200fd4e docs: indicate eslintrc mode for .eslintignore (#18285) (Francesco Trotta)
16b6a8b docs: Update README (GitHub Actions Bot)
df5f8a9 docs: paths and patterns difference in no-restricted-imports (#18273) (Tanuj Kanti)
c537d76 docs: update npm init @eslint/config generated file names (#18298) (唯然)
e1e305d docs: fix linebreak-style examples (#18262) (Francesco Trotta)
113f51e docs: Mention package.json config support dropped (#18305) (Nicholas C. Zakas)
5c35321 docs: add eslintrc-only note to --rulesdir (#18281) (Adam Lui 刘展鹏)

1fa6622 build: do not use --force flag to install dependencies (#18284) (Francesco Trotta)

Chores

d9a2983 chore: upgrade @eslint/js to v9.1.1 (#18367) (Francesco Trotta)
50d406d chore: package.json update for @eslint/js release (Jenkins)
155c71c chore: package.json update for @eslint/js release (Jenkins)
0588fc5 refactor: Move directive gathering to SourceCode (#18328) (Nicholas C. Zakas)
9048e21 chore: lint docs/src/_data js files (#18335) (Milos Djermanovic)
4820790 chore: upgrade globals@15.0.0 dev dependency (#18332) (Milos Djermanovic)
698d9ff chore: upgrade jsdoc & unicorn plugins in eslint-config-eslint (#18333) (Milos Djermanovic)
32c08cf chore: drop Node < 18 and use @eslint/js v9 in eslint-config-eslint (#18323) (Milos Djermanovic)
a76fb55 chore: @eslint-community/eslint-plugin-eslint-comments v4.3.0 (#18319) (Milos Djermanovic)
78e45b1 chore: eslint-plugin-eslint-plugin v6.0.0 (#18316) (唯然)
36103a5 chore: eslint-plugin-n v17.0.0 (#18315) (唯然)

ESLint v9.0.0 released

2024-04-05T00:00:00Z

Highlights

This is a summary of the significant changes, both breaking and non-breaking, you need to know about when upgrading from ESLint v8.x to ESLint v9.0.0.

Installing

Because this is a major release, you may not automatically be upgraded by npm. To ensure you are using this version, run:

npm i eslint@9.0.0 --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the breaking changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Node.js < v18.18.0, v19 no longer supported

As of this post, Node.js v20.x is the LTS release, and as such we are dropping support for all versions of Node.js prior to v18.18.0 as well as v19.x.

Flat config is now the default and has some changes

Flat config is now the default configuration format for ESLint and eslintrc is officially deprecated. To continue using a eslintrc configuration file, you’ll need to set the ESLINT_USE_FLAT_CONFIG environment variable to false.

This change affects users, plugin developers, and integrators as many aspects of ESLint had to change to make this happen. Please see our previous blog post for more details.

This release also introduces the config inspector, which can be launched on the command line using --inspect-config.

Removed all formatters except `stylish`, `html`, `json`, and `json-with-meta`

The following formatters have been removed:

checkstyle
compact
jslint-xml
junit
tap
unix
visualstudio

If you are using these formatters currently, you’ll need to install the standalone packages for use with ESLint v9.0.0.

Removed `valid-jsdoc` and `require-jsdoc` rules

We have removed valid-jsdoc and require-jsdoc. We recommend using the eslint-plugin-jsdoc plugin instead.

Removed deprecated methods on `context` and `SourceCode`

As we announced in September, we have removed a lot of deprecated methods from context and replaced them with methods on SourceCode.

Updated `eslint:recommended`

The eslint:recommended configuration is updated to include new rules that we feel are important, and to remove deprecated and less important rules.

New rule: `no-useless-assignment`

ESLint v9.0.0 introduces a new rule, no-useless-assignment, that is designed to catch situations where you’ve assigned a value to a variable and that value is never used. For example:

let id = 1234;      // 1234 is never used
id = calculateId();

Updates to existing rules

The complexity rule now also takes into account optional chaining and default values in destructuring patterns and parameters.
The no-fallthrough rule has a new option reportUnusedFallthroughComment.
The no-inner-declarations rule has a new default behavior. In v8.x, the rule would flag any functions defined inside of blocks as errors because this behavior was undefined in early versions of JavaScript. As of ES 2015, block-scoped function declarations are well-defined and so we changed the default behavior to not warn on block-scoped functions.
The no-misleading-character-class rule now highlights the offending characters in a regular expression rather than the entire regular expression.
The no-restricted-imports rule changed the behavior of paths. In v8.x, if multiple entries in the paths array of your configuration for The no-restricted-imports rule had the same name property, only the last one would apply. In v9.0.0, all entries apply, allowing for specifying different error messages for different imported names.
The no-restricted-imports rule has new options allowImportNames and allowImportNamePattern.
The no-unused-vars rule varsIgnorePattern option no longer applies to caught error variables.
The no-unused-vars rule has a new default value for the caughtErrors option (changed from "none" to "all").
The no-unused-vars rule has a new option ignoreClassWithStaticInitBlock.
The no-unused-vars rule has a new option reportUsedIgnorePattern.
The no-useless-computed-key rule has a new default value for the enforceForClassMembers option (changed from false to true). This is intended to help avoiding misleading comments that can occur as a result of refactoring. When this option is set to true, the rule will prohibit a fallthrough comment if a case can never fallthrough.

New API `loadESLint()`

ESLint now exports a new function loadESLint() from its main entry point. Integrations can use this function to get either the ESLint class (former FlatESLint class) or the LegacyESLint class (former ESLint class) and thus easily swap between flat config and eslintrc APIs.

Changes to how you write rules

We’ve made multiple changes to help prevent errors in rules:

Function-style rules will stop working in v9.0.0. Function-style rules are rules created by exporting a function from a file rather than exporting an object with a create() method.
When a rule doesn’t have meta.schema specified, a default schema of [] will be applied. This means that rules without a schema will be assumed to have no options, which in turn means that validation will fail if options are provided.

Stricter `RuleTester` validations

This release adds more checks in RuleTester:

Messages cannot have unsubstituted placeholders.
Suggestions must change the code.
Suggestion messages must be unique for the same lint problem.
Suggestions must generate valid syntax.
Test case output must be different from code.
Test error objects must specify message or messageId.
Test error object must specify suggestions if the actual error provides suggestions.
Test suggestion objects must specify desc or messageId.
Test suggestion objects must specify output.
filename and only properties of test objects must be of the expected type (string and boolean, respectively).
Duplicate tests cause an error.

The `--output-file` flag now guarantees a file is output

The --output-file CLI flag is designed to output the results of the ESLint run to specified file. Prior to this release, no file would be output if linting passed with no errors or warnings. In v9.0.0, an empty file will be output when linting passes without any errors or warnings.

Better scope analysis

In v9.0.0, we updated the behavior of eslint-scope to fix a couple of longstanding bugs:

Previously, ESLint would treat ("use strict") as a strict mode directive even though it is not. We fixed the behavior so only valid strict mode directives are honored.
The containing scope of a class extends clause was incorrectly set to be the scope containing the class when it should have been the class scope itself. This has been fixed.

`CodePath#currentSegments` removed

As announced in our previous post, CodePath#currentSegments has been removed from the rules API. Please refer to the post for more details.

Precalculated Code Paths

ESLint v9.0.0 now precalculates code path information before the traversal used by rules. As a result, the code path information is now complete regardless of where it is accessed inside of a rule.

Multiple `/* eslint */` comments for the same rule are now disallowed

In ESLint v8.x, if the file being linted contained multiple /* eslint */ configuration comments for the same rule, the last one would be applied, while the others would be silently ignored.

In ESLint v9.0.0, the first one is applied, while the others are reported as lint errors.

`--quiet` option is more performant

The --quiet option hides all warnings in the ESLint console. In v9.0.0, we are making a performance improvement by also not executing any rules set to "warn".

Running `eslint` with no file arguments

If you are using flat config and you don’t pass any file arguments to the CLI, the CLI will default to linting the current directory, which means you can type npx eslint and it will just work. (Doing the same with an eslintrc config file will result in an error.)

Unused disable directives cause warnings by default

ESLint has long been able to flag unused disable directives. In this release, we’ve enabled warnings for unused disable directives by default. You can modify this value in your config file with linterOptions.reportUnusedDisableDirectives or on the command line using --report-unused-disable-directives-severity.

Performance statistics available in formatters via `--stats`

The information from the rule profiler is now available inside of formatters when the --stats flag is used in the CLI. This allows anyone to create custom visualizations of the performance information that ESLint tracks.

Breaking Changes

b7cf3bd fix!: correct camelcase rule schema for allow option (#18232) (eMerzh)
09bd7fe feat!: move AST traversal into SourceCode (#18167) (Nicholas C. Zakas)
79a95eb feat!: disallow multiple configuration comments for same rule (#18157) (Milos Djermanovic)
9163646 feat!: Rule Tester checks for missing placeholder data in the message (#18073) (fnx)
3c4d51d feat!: default for enforceForClassMembers in no-useless-computed-key (#18054) (Francesco Trotta)
47e60f8 feat!: Stricter rule test validations (#17654) (fnx)
1a94589 feat!: no-unused-vars default caughtErrors to ‘all’ (#18043) (Josh Goldberg ✨)
57089cb feat!: no-restricted-imports allow multiple config entries for same path (#18021) (Milos Djermanovic)
2e1d549 feat!: detect duplicate test cases (#17955) (Bryan Mishkin)
701f1af feat!: no-inner-declaration new default behaviour and option (#17885) (Tanuj Kanti)
bde5105 fix!: handle --output-file for empty output when saving to disk (#17957) (Nitin Kumar)
07107a5 fix!: upgrade eslint-scope@8.0.0 (#17942) (Milos Djermanovic)
3ee0f6c fix!: no-unused-vars varsIgnorePattern behavior with catch arguments (#17932) (Tanuj Kanti)
51f8bc8 fix!: configuration comments with just severity should retain options (#17945) (Milos Djermanovic)
d191bdd feat!: Remove CodePath#currentSegments (#17936) (Milos Djermanovic)
946ae00 feat!: FlatRuleTester -> RuleTester (#17922) (Nicholas C. Zakas)
baff28c feat!: remove no-inner-declarations from eslint:recommended (#17920) (Milos Djermanovic)
cadfbcd feat!: Rename FlatESLint to ESLint (#17914) (Nicholas C. Zakas)
d1018fc feat!: skip running warnings in --quiet mode (#17274) (Maddy Miller)
fb81b1c feat!: Set default schema: [], drop support for function-style rules (#17792) (Milos Djermanovic)
0b21e1f feat!: add two more cases to no-implicit-coercion (#17832) (Gürgün Dayıoğlu)
2916c63 feat!: Switch Linter to flat config by default (#17851) (Nicholas C. Zakas)
200518e fix!: Parsing ‘exported’ comment using parseListConfig (#17675) (amondev)
bdd6ba1 feat!: Remove valid-jsdoc and require-jsdoc (#17694) (Nicholas C. Zakas)
12be307 fix!: Behavior of CLI when no arguments are passed (#17644) (Nicholas C. Zakas)
8fe8c56 feat!: Update shouldUseFlatConfig and CLI so flat config is default (#17748) (Nicholas C. Zakas)
60dea3e feat!: deprecate no-new-symbol, recommend no-new-native-nonconstructor (#17710) (Francesco Trotta)
5aa9c49 feat!: check for parsing errors in suggestion fixes (#16639) (Bryan Mishkin)
b3e0bb0 feat!: assert suggestion messages are unique in rule testers (#17532) (Josh Goldberg ✨)
e563c52 feat!: no-invalid-regexp make allowConstructorFlags case-sensitive (#17533) (Josh Goldberg ✨)
e5f02c7 fix!: no-sequences rule schema correction (#17878) (MHO)
6ee3e9e feat!: Update eslint:recommended configuration (#17716) (Milos Djermanovic)
c2cf85a feat!: drop support for string configurations in flat config array (#17717) (Milos Djermanovic)
c314fd6 feat!: Remove SourceCode#getComments() (#17715) (Milos Djermanovic)
ae78ff1 feat!: Remove deprecated context methods (#17698) (Nicholas C. Zakas)
f71c328 feat!: Swap FlatESLint-ESLint, FlatRuleTester-RuleTester in API (#17823) (Nicholas C. Zakas)
5304da0 feat!: remove formatters except html, json(-with-metadata), and stylish (#17531) (Josh Goldberg ✨)
e1e827f feat!: Require Node.js ^18.18.0 || ^20.9.0 || >=21.1.0 (#17725) (Milos Djermanovic)

Features

d54a412 feat: Add --inspect-config CLI flag (#18270) (Nicholas C. Zakas)
97ce45b feat: Add reportUsedIgnorePattern option to no-unused-vars rule (#17662) (Pearce Ropion)
3e9fcea feat: Show config names in error messages (#18256) (Nicholas C. Zakas)
de40874 feat: Rule Performance Statistics for flat ESLint (#17850) (Mara Kiefer)
d85c436 feat: use-isnan report NaN in indexOf and lastIndexOf with fromIndex (#18225) (Tanuj Kanti)
b8fb572 feat: add reportUnusedFallthroughComment option to no-fallthrough rule (#18188) (Kirk Waiblinger)
1c173dc feat: add ignoreClassWithStaticInitBlock option to no-unused-vars (#18170) (Tanuj Kanti)
a451b32 feat: make no-misleading-character-class report more granular errors (#18082) (Francesco Trotta)
c49ed63 feat: update complexity rule for optional chaining & default values (#18152) (Mathias Schreck)
11144a2 feat: no-restricted-imports option added allowImportNames (#16196) (M Pater)
74124c2 feat: add suggestions to use-isnan in indexOf & lastIndexOf calls (#18063) (StyleShit)
53f0f47 feat: Add loadESLint() API method for v9 (#18097) (Nicholas C. Zakas)
2d11d46 feat: add suggestions to use-isnan in binary expressions (#17996) (StyleShit)
26093c7 feat: fix false negatives in no-this-before-super (#17762) (Yosuke Ota)
5471e43 feat: convert unsafe autofixes to suggestions in no-implicit-coercion (#17985) (Gürgün Dayıoğlu)
e3051be feat: emit warning when .eslintignore file is detected (#17952) (Nitin Kumar)
a630edd feat: maintain latest ecma version in ESLint (#17958) (Milos Djermanovic)
b4e0503 feat: add no-useless-assignment rule (#17625) (Yosuke Ota)
287c4b7 feat: no-misleading-character-class granular errors (#17515) (Josh Goldberg ✨)
8792464 feat: Enable eslint.config.mjs and eslint.config.cjs (#17909) (Nicholas C. Zakas)
24ce927 feat: warn by default for unused disable directives (#17879) (Bryan Mishkin)

Bug Fixes

610c148 fix: Support using declarations in no-lone-blocks (#18269) (Kirk Waiblinger)
e508800 fix: rule tester ignore irrelevant test case properties (#18235) (fnx)
a129acb fix: flat config name on ignores object (#18258) (Nicholas C. Zakas)
dadc5bf fix: constructor-super false positives with loops (#18226) (Milos Djermanovic)
ae8103d fix: load plugins in the CLI in flat config mode (#18185) (Francesco Trotta)
e37153f fix: improve error message for invalid rule config (#18147) (Nitin Kumar)
af6e170 fix: stop linting files after an error (#18155) (Francesco Trotta)
0cb4914 fix: validate options when comment with just severity enables rule (#18133) (Milos Djermanovic)
c4d26fd fix: use-isnan doesn’t report on SequenceExpressions (#18059) (StyleShit)
39076fb fix: handle absolute file paths in RuleTester (#17989) (Nitin Kumar)
6d11f3d fix: Ensure config keys are printed for config errors (#17980) (Nicholas C. Zakas)
806f708 fix: no-misleading-character-class edge cases with granular errors (#17970) (Milos Djermanovic)
f182114 fix: deep merge behavior in flat config (#17906) (Francesco Trotta)
b577e8a fix: allow circular references in config (#17752) (Francesco Trotta)

Documentation

e151050 docs: update get-started to the new @eslint/create-config (#18217) (唯然)
94178ad docs: mention about name field in flat config (#18252) (Anthony Fu)
1765c24 docs: add Troubleshooting page (#18181) (Josh Goldberg ✨)
96607d0 docs: version selectors synchronization (#18260) (Milos Djermanovic)
651ec91 docs: remove /* eslint-env */ comments from rule examples (#18249) (Milos Djermanovic)
950c4f1 docs: Update README (GitHub Actions Bot)
12f5746 docs: add info about dot files and dir in flat config (#18239) (Tanuj Kanti)
b93f408 docs: update shared settings example (#18251) (Tanuj Kanti)
26384d3 docs: fix ecmaVersion in one example, add checks (#18241) (Milos Djermanovic)
7747097 docs: Update PR review process (#18233) (Nicholas C. Zakas)
b07d427 docs: fix typo (#18246) (Kirill Gavrilov)
778082d docs: add Glossary page (#18187) (Josh Goldberg ✨)
239a7e2 docs: Clarify the description of sort-imports options (#18198) (gyeongwoo park)
4769c86 docs: fix incorrect example in no-lone-blocks (#18215) (Tanuj Kanti)
5251327 docs: Update README (GitHub Actions Bot)
1dc8618 docs: Update README (GitHub Actions Bot)
ba1c1bb docs: Update README (GitHub Actions Bot)
337cdf9 docs: Explain limitations of RuleTester fix testing (#18175) (Nicholas C. Zakas)
c7abd89 docs: Explain Node.js version support (#18176) (Nicholas C. Zakas)
d961eeb docs: show red underlines in examples in rules docs (#18041) (Yosuke Ota)
558274a docs: Update README (GitHub Actions Bot)
2908b9b docs: Update release documentation (#18174) (Nicholas C. Zakas)
1f1260e docs: replace HackerOne link with GitHub advisory (#18165) (Francesco Trotta)
e5ef3cd docs: add inline cases condition in no-fallthrough (#18158) (Tanuj Kanti)
450d0f0 docs: fix ignore option docs (#18154) (Francesco Trotta)
5fe095c docs: show v8.57.0 as latest version in dropdown (#18142) (Milos Djermanovic)
7db5bb2 docs: Show prerelease version in dropdown (#18135) (Nicholas C. Zakas)
73a5f06 docs: Update README (GitHub Actions Bot)
f95cd27 docs: Disallow multiple rule configuration comments in the same example (#18116) (Milos Djermanovic)
d8068ec docs: Update link for schema examples (#18112) (Svetlana)
f1c7e6f docs: Switch to Ethical Ads (#18090) (Strek)
15c143f docs: JS Foundation -> OpenJS Foundation in PR template (#18092) (Nicholas C. Zakas)
6ea339e docs: add stricter rule test validations to v9 migration guide (#18085) (Milos Djermanovic)
3c816f1 docs: use relative link from CLI to core concepts (#18083) (Milos Djermanovic)
9458735 docs: fix malformed eslint config comments in rule examples (#18078) (Francesco Trotta)
07a1ada docs: link from --fix CLI doc to the relevant core concept (#18080) (Bryan Mishkin)
b844324 docs: Update team responsibilities (#18048) (Nicholas C. Zakas)
aadfb60 docs: document languageOptions and other v9 changes for context (#18074) (fnx)
857e242 docs: tweak explanation for meta.docs rule properties (#18057) (Bryan Mishkin)
10485e8 docs: recommend messageId over message for reporting rule violations (#18050) (Bryan Mishkin)
98b5ab4 docs: Update README (GitHub Actions Bot)
505fbf4 docs: update no-restricted-imports rule (#18015) (Tanuj Kanti)
c25b4af docs: Update README (GitHub Actions Bot)
33d1ab0 docs: add more examples to flat config ignores docs (#18020) (Milos Djermanovic)
e6eebca docs: Update sort-keys options properties count (#18025) (LB (Ben Johnston))
1fedfd2 docs: Improve flat config ignores docs (#17997) (Nicholas C. Zakas)
38b9b06 docs: update valid-typeof rule (#18001) (Tanuj Kanti)
b4abfea docs: Update note about ECMAScript support (#17991) (Francesco Trotta)
6788873 docs: Update release blog post template (#17994) (Nicholas C. Zakas)
1f37442 docs: Add sections on non-npm plugin configuration (#17984) (Nicholas C. Zakas)
96307da docs: migration guide entry for no-inner-declarations (#17977) (Tanuj Kanti)
40be60e docs: Update README (GitHub Actions Bot)
d31c180 docs: fix number of code-path events on custom rules page (#17969) (Richard Hunter)
1529ab2 docs: reorder entries in v9 migration guide (#17967) (Milos Djermanovic)
9507525 docs: Explain how to combine configs (#17947) (Nicholas C. Zakas)
7c78576 docs: Add more removed context methods to migrate to v9 guide (#17951) (Milos Djermanovic)
3a877d6 docs: Update removed CLI flags migration (#17939) (Nicholas C. Zakas)
4a9cd1e docs: Update Linter API for v9 (#17937) (Milos Djermanovic)
2a8eea8 docs: update docs for v9.0.0-alpha.0 (#17929) (Milos Djermanovic)
7f0ba51 docs: show NEXT in version selectors (#17911) (Milos Djermanovic)
0a7911e docs: add flat config default to v9 migration guide (#17927) (Milos Djermanovic)
94f8065 docs: Add CLI updates to migrate to v9 guide (#17924) (Nicholas C. Zakas)
16187f2 docs: Add exported and string config notes to migrate to v9 guide (#17926) (Nicholas C. Zakas)
3ae50cc docs: Add RuleTester changes to migrate to v9 guide (#17923) (Nicholas C. Zakas)
0831b58 docs: add rule changes to v9 migration guide (#17925) (Milos Djermanovic)
037abfc docs: update API docs (#17919) (Milos Djermanovic)
afc3c03 docs: add function-style and meta.schema changes to v9 migration guide (#17912) (Milos Djermanovic)
1da0723 docs: update eslint:recommended section in Migrate to v9.x (#17908) (Milos Djermanovic)
f55881f docs: remove configuration-files-new.md (#17907) (Milos Djermanovic)
63ae191 docs: Migrate to v9.0.0 (#17905) (Nicholas C. Zakas)
e708496 docs: Switch to flat config by default (#17840) (Nicholas C. Zakas)
fdf0424 docs: Update Create a Plugin for flat config (#17826) (Nicholas C. Zakas)
e6a91bd docs: Switch shareable config docs to use flat config (#17827) (Nicholas C. Zakas)
3831fb7 docs: updated examples of max-lines rule (#17898) (Tanuj Kanti)
cd1ac20 docs: Update README (GitHub Actions Bot)

26010c2 Build: changelog update for 9.0.0-rc.0 (Jenkins)
b91f9dc build: fix TypeError in prism-eslint-hooks.js (#18209) (Francesco Trotta)
d7ec0d1 Build: changelog update for 9.0.0-beta.2 (Jenkins)
fd9c0a9 Build: changelog update for 9.0.0-beta.1 (Jenkins)
c9f2f33 build: changelog update for 8.57.0 (#18144) (Milos Djermanovic)
1bbc495 Build: changelog update for 9.0.0-beta.0 (Jenkins)
96f8877 Build: changelog update for 9.0.0-alpha.2 (Jenkins)
52d5e7a Build: changelog update for 9.0.0-alpha.1 (Jenkins)
c2bf27d build: update docs files when publishing prereleases (#17940) (Milos Djermanovic)
e91d85d Build: changelog update for 9.0.0-alpha.0 (Jenkins)

Chores

19f9a89 chore: Update dependencies for v9.0.0 (#18275) (Nicholas C. Zakas)
7c957f2 chore: package.json update for @eslint/js release (Jenkins)
d73a33c chore: ignore /docs/v8.x in link checker (#18274) (Milos Djermanovic)
44a81c6 chore: upgrade knip (#18272) (Lars Kappert)
e80b60c chore: remove code for testing version selectors (#18266) (Milos Djermanovic)
a98babc chore: add npm script to run WebdriverIO test (#18238) (Francesco Trotta)
9b7bd3b chore: update dependency markdownlint to ^0.34.0 (#18237) (renovate[bot])
297416d chore: package.json update for eslint-9.0.0-rc.0 (#18223) (Francesco Trotta)
d363c51 chore: package.json update for @eslint/js release (Jenkins)
1b841bb chore: fix some comments (#18213) (avoidaway)
29c3595 chore: remove repetitive words (#18193) (cuithon)
acc2e06 chore: Introduce Knip (#18005) (Lars Kappert)
7509276 chore: upgrade @eslint/js@9.0.0-beta.2 (#18180) (Milos Djermanovic)
96087b3 chore: package.json update for @eslint/js release (Jenkins)
925afa2 chore: Remove some uses of lodash.merge (#18179) (Milos Djermanovic)
972ef15 chore: remove invalid type in @eslint/js (#18164) (Nitin Kumar)
32ffdd1 chore: upgrade @eslint/js@9.0.0-beta.1 (#18146) (Milos Djermanovic)
e41425b chore: package.json update for @eslint/js release (Jenkins)
bb3b9c6 chore: upgrade @eslint/eslintrc@3.0.2 (#18145) (Milos Djermanovic)
e462524 chore: upgrade eslint-release@3.2.2 (#18138) (Milos Djermanovic)
8e13a6b chore: fix spelling mistake in README.md (#18128) (Will Eastcott)
66f52e2 chore: remove unused tools rule-types.json, update-rule-types.js (#18125) (Josh Goldberg ✨)
bf0c7ef ci: fix sync-labels value of pr-labeler (#18124) (Tanuj Kanti)
cace6d0 ci: add PR labeler action (#18109) (Nitin Kumar)
1a65d3e chore: export base config from eslint-config-eslint (#18119) (Milos Djermanovic)
9aa4df3 refactor: remove globals dependency (#18115) (Milos Djermanovic)
e40d1d7 chore: upgrade @eslint/js@9.0.0-beta.0 (#18108) (Milos Djermanovic)
9870f93 chore: package.json update for @eslint/js release (Jenkins)
2c62e79 chore: upgrade @eslint/eslintrc@3.0.1 (#18107) (Milos Djermanovic)
81f0294 chore: upgrade espree@10.0.1 (#18106) (Milos Djermanovic)
5e2b292 chore: upgrade eslint-visitor-keys@4.0.0 (#18105) (Milos Djermanovic)
ce838ad chore: replace dependency npm-run-all with npm-run-all2 ^5.0.0 (#18045) (renovate[bot])
54df731 chore: update dependency markdownlint-cli to ^0.39.0 (#18084) (renovate[bot])
8f06a60 chore: update dependency shelljs to ^0.8.5 (#18079) (Francesco Trotta)
93ffe30 chore: update dependency file-entry-cache to v8 (#17903) (renovate[bot])
6ffdcbb chore: upgrade @eslint/js@9.0.0-alpha.2 (#18038) (Milos Djermanovic)
2c12715 chore: package.json update for @eslint/js release (Jenkins)
cc74c4d chore: upgrade espree@10.0.0 (#18037) (Milos Djermanovic)
dfb68b6 chore: use Node.js 20 for docs sites (#18026) (Milos Djermanovic)
8c1b8dd test: add more tests for ignoring files and directories (#18018) (Milos Djermanovic)
60b966b chore: update dependency @eslint/js to v9.0.0-alpha.1 (#18014) (renovate[bot])
c893bc0 chore: update markdownlint to v0.33.0 (#17995) (Nitin Kumar)
c5e50ee chore: package.json update for @eslint/js release (Jenkins)
1bf2520 chore: Split Docs CI from core CI (#17897) (Nicholas C. Zakas)
320787e chore: delete relative-module-resolver.js (#17981) (Francesco Trotta)
4926f33 refactor: use Object.hasOwn() (#17948) (Milos Djermanovic)
df200e1 refactor: use Array.prototype.at() to get last elements (#17949) (Milos Djermanovic)
750b8df chore: update dependency glob to v10 (#17917) (renovate[bot])
74794f5 chore: removed unused eslintrc modules (#17938) (Milos Djermanovic)
10ed29c chore: remove unused dependency rimraf (#17934) (Francesco Trotta)
903ee60 ci: use --force flag when installing eslint (#17921) (Milos Djermanovic)
17fedc1 chore: upgrade @eslint/js@9.0.0-alpha.0 (#17928) (Milos Djermanovic)
cb89ef3 chore: package.json update for @eslint/js release (Jenkins)
f6f4a45 chore: drop structuredClone polyfill for v9 (#17915) (Kevin Gibbons)
412dcbb chore: upgrade eslint-plugin-n@16.6.0 (#17916) (Milos Djermanovic)
02a8baf chore: Rename files with underscores (#17910) (Nicholas C. Zakas)
c0f5d91 chore: remove creating an unused instance of Linter in tests (#17902) (Milos Djermanovic)
3826cdf chore: use jsdoc/no-multi-asterisks with allowWhitespace: true (#17900) (Percy Ma)
a9a17b3 chore: fix getting scope in tests (#17899) (Milos Djermanovic)
595a1f6 test: ensure that CLI tests run with FlatESLint (#17884) (Francesco Trotta)
c7eca43 chore: update dependency markdownlint-cli to ^0.38.0 (#17865) (renovate[bot])
cc0c9f7 ci: bump github/codeql-action from 2 to 3 (#17873) (dependabot[bot])

Introducing ESLint Config Inspector

2024-04-05T00:00:00Z

As of ESLint v9,0.0, the new configuration system has reached general availability, bringing with it many benefits. Configuration files are now easier to manage and more transparent to compose. However, it can still be non-trivial to understand which rules are enabled and disabled for specific files, especially when your configuration is complex or composed from multiple sources. That’s why we are excited to introduce the ESLint Config Inspector, a visual and interactive tool to help you better understand and inspect your config file.

Give it a Try!

ESLint Config Inspector is a CLI command that fires up a local web server to visualize your ESLint configuration file from your local filesystem. Give it a try:

eslint --inspect-config

Or you can run the config inspector without ESLint installed by running the following command in the root directory that contains eslint.config.js file:

npx @eslint/config-inspector

Visit http://localhost:7777 in your browser, and you will see a visual representation of your ESLint configuration file. You can then navigate through the rules, plugins, and language configurations that are enabled or disabled. Changes made to your local configuration file will also be reflected in automatically in the inspector.

Features

Here are some of the key features that the ESLint Config Inspector provides:

Config Items Overview

In the “Configs” tab, you will see a list of all configuration objects from your configuration file. This is especially useful when you are including external configurations or have dynamically generated configurations. This feature gives you the transparency to see how those configurations are resolved and augmented in your project.

Filepath Matching

In the “Configs” tab, you can enter a file path to see which rules are enabled or disabled for that specific file:

You can also toggle the view to see the final merged rules for that file:

Available Rules

Go to the “Rules” tab to see all the available rules from the plugins you have installed. Each rule displays if it is enabled or disabled in your configuration file. You can also filter rules to find the usage of deprecated rules or recommended rules that are not yet enabled.

Conclusion

We hope that the ESLint Config Inspector will make understanding and maintaining your ESLint configurations easier and more enjoyable. We are excited to hear your feedback and suggestions on how we can improve the tool further. Please feel free to open an issue to share your thoughts.

ESLint v9.0.0-rc.0 released

2024-03-22T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-rc.0 --save-dev

Migration Guide

Precalculated Code Paths

ESLint v9.0.0 now precalculates code path information before the traversal used by rules. As a result, the code path information is now complete regardless of where it is accessed inside of a rule.

Disallow Unused `// fallthrough` Comments

In ESLint v9.0.0-rc.0, the rule no-fallthrough has a new option reportUnusedFallthroughComment. When this option is set to true, the rule will prohibit a fallthrough comment if a case can never fallthrough. This is intended to help avoiding misleading comments that can occur as a result of refactoring.

Breaking Changes

09bd7fe feat!: move AST traversal into SourceCode (#18167) (Nicholas C. Zakas)

Features

b8fb572 feat: add reportUnusedFallthroughComment option to no-fallthrough rule (#18188) (Kirk Waiblinger)

Bug Fixes

ae8103d fix: load plugins in the CLI in flat config mode (#18185) (Francesco Trotta)

Documentation

239a7e2 docs: Clarify the description of sort-imports options (#18198) (gyeongwoo park)
4769c86 docs: fix incorrect example in no-lone-blocks (#18215) (Tanuj Kanti)
5251327 docs: Update README (GitHub Actions Bot)
1dc8618 docs: Update README (GitHub Actions Bot)

b91f9dc build: fix TypeError in prism-eslint-hooks.js (#18209) (Francesco Trotta)

Chores

297416d chore: package.json update for eslint-9.0.0-rc.0 (#18223) (Francesco Trotta)
d363c51 chore: package.json update for @eslint/js release (Jenkins)
1b841bb chore: fix some comments (#18213) (avoidaway)
29c3595 chore: remove repetitive words (#18193) (cuithon)
acc2e06 chore: Introduce Knip (#18005) (Lars Kappert)

ESLint v9.0.0-beta.2 released

2024-03-08T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-beta.2 --save-dev

Migration Guide

Multiple `/* eslint */` comments for the same rule are now disallowed

In ESLint v8.x, if the file being linted contained multiple /* eslint */ configuration comments for the same rule, the last one would be applied, while the others would be silently ignored.

In ESLint v9.0.0, the first one is applied, while the others are reported as lint errors.

New Features

The no-restricted-imports rule has new options allowImportNames and allowImportNamePattern.
The no-unused-vars rule has a new option ignoreClassWithStaticInitBlock.
The complexity rule now also takes into account optional chaining and default values in destructuring patterns and parameters.

Breaking Changes

79a95eb feat!: disallow multiple configuration comments for same rule (#18157) (Milos Djermanovic)

Features

1c173dc feat: add ignoreClassWithStaticInitBlock option to no-unused-vars (#18170) (Tanuj Kanti)
a451b32 feat: make no-misleading-character-class report more granular errors (#18082) (Francesco Trotta)
c49ed63 feat: update complexity rule for optional chaining & default values (#18152) (Mathias Schreck)
11144a2 feat: no-restricted-imports option added allowImportNames (#16196) (M Pater)

Bug Fixes

e37153f fix: improve error message for invalid rule config (#18147) (Nitin Kumar)
af6e170 fix: stop linting files after an error (#18155) (Francesco Trotta)

Documentation

ba1c1bb docs: Update README (GitHub Actions Bot)
337cdf9 docs: Explain limitations of RuleTester fix testing (#18175) (Nicholas C. Zakas)
c7abd89 docs: Explain Node.js version support (#18176) (Nicholas C. Zakas)
d961eeb docs: show red underlines in examples in rules docs (#18041) (Yosuke Ota)
558274a docs: Update README (GitHub Actions Bot)
2908b9b docs: Update release documentation (#18174) (Nicholas C. Zakas)
1f1260e docs: replace HackerOne link with GitHub advisory (#18165) (Francesco Trotta)
e5ef3cd docs: add inline cases condition in no-fallthrough (#18158) (Tanuj Kanti)
450d0f0 docs: fix ignore option docs (#18154) (Francesco Trotta)

Chores

7509276 chore: upgrade @eslint/js@9.0.0-beta.2 (#18180) (Milos Djermanovic)
96087b3 chore: package.json update for @eslint/js release (Jenkins)
925afa2 chore: Remove some uses of lodash.merge (#18179) (Milos Djermanovic)
972ef15 chore: remove invalid type in @eslint/js (#18164) (Nitin Kumar)

ESLint v9.0.0-beta.1 released

2024-02-23T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-beta.1 --save-dev

Migration Guide

Features

74124c2 feat: add suggestions to use-isnan in indexOf & lastIndexOf calls (#18063) (StyleShit)

Bug Fixes

0cb4914 fix: validate options when comment with just severity enables rule (#18133) (Milos Djermanovic)

Documentation

5fe095c docs: show v8.57.0 as latest version in dropdown (#18142) (Milos Djermanovic)
7db5bb2 docs: Show prerelease version in dropdown (#18135) (Nicholas C. Zakas)
73a5f06 docs: Update README (GitHub Actions Bot)
f95cd27 docs: Disallow multiple rule configuration comments in the same example (#18116) (Milos Djermanovic)
d8068ec docs: Update link for schema examples (#18112) (Svetlana)

c9f2f33 build: changelog update for 8.57.0 (#18144) (Milos Djermanovic)

Chores

32ffdd1 chore: upgrade @eslint/js@9.0.0-beta.1 (#18146) (Milos Djermanovic)
e41425b chore: package.json update for @eslint/js release (Jenkins)
bb3b9c6 chore: upgrade @eslint/eslintrc@3.0.2 (#18145) (Milos Djermanovic)
e462524 chore: upgrade eslint-release@3.2.2 (#18138) (Milos Djermanovic)
8e13a6b chore: fix spelling mistake in README.md (#18128) (Will Eastcott)
66f52e2 chore: remove unused tools rule-types.json, update-rule-types.js (#18125) (Josh Goldberg ✨)
bf0c7ef ci: fix sync-labels value of pr-labeler (#18124) (Tanuj Kanti)
cace6d0 ci: add PR labeler action (#18109) (Nitin Kumar)
1a65d3e chore: export base config from eslint-config-eslint (#18119) (Milos Djermanovic)
9aa4df3 refactor: remove globals dependency (#18115) (Milos Djermanovic)

ESLint v8.57.0 released

2024-02-23T00:00:00Z

Highlights

This release backports from v9.x to v8.x two new features and several bug fixes related to the flat config system to help plugins, integrations and users migrate to flat config ahead of the final v9.0.0 release.

Support for `eslint.config.mjs` and `eslint.config.cjs`

This release introduces support for eslint.config.mjs and eslint.config.cjs configuration files to v8.x in addition to eslint.config.js, making it easier to use the module format you’d prefer regardless of the module format of the containing package.

New API `loadESLint()`

ESLint now exports a new function loadESLint() from its main entry point. Integrations can use this function to get either the FlatESLint class (ESLint class in v9.x) or the ESLint class (LegacyESLint class in v9.x) and thus easily swap between flat config and eslintrc APIs.

Features

1120b9b feat: Add loadESLint() API method for v8 (#18098) (Nicholas C. Zakas)
dca7d0f feat: Enable eslint.config.mjs and eslint.config.cjs (#18066) (Nitin Kumar)

Bug Fixes

2196d97 fix: handle absolute file paths in FlatRuleTester (#18064) (Nitin Kumar)
69dd1d1 fix: Ensure config keys are printed for config errors (#18067) (Nitin Kumar)
9852a31 fix: deep merge behavior in flat config (#18065) (Nitin Kumar)
4c7e9b0 fix: allow circular references in config (#18056) (Milos Djermanovic)

Documentation

84922d0 docs: Show prerelease version in dropdown (#18139) (Nicholas C. Zakas)
5b8c363 docs: Switch to Ethical Ads (#18117) (Milos Djermanovic)
77dbfd9 docs: show NEXT in version selectors (#18052) (Milos Djermanovic)

Chores

1813aec chore: upgrade @eslint/js@8.57.0 (#18143) (Milos Djermanovic)
5c356bb chore: package.json update for @eslint/js release (Jenkins)
f4a1fe2 test: add more tests for ignoring files and directories (#18068) (Nitin Kumar)
42c0aef ci: Enable CI for v8.x branch (#18047) (Milos Djermanovic)

ESLint's 2023 year in review

2024-02-21T00:00:00Z

The plan for 2023 centered around our first major release since 2021, ESLint v9.0.0. Most of the year was spent preparing for the release, building out the new configuration system (flat config) and communicating the impact to the ecosystem throughout the year.

Release of ESLint v9.0.0 and the new configuration system

While there are a lot of changes in v9.0.0, the biggest change is making flat config the default configuration system. The old (eslintrc) configuration is still available via an environment variable, and we published the rollout plan outlining how the transition will occur from v8.x through to v10.x.

Just before the end of the year, we released ESLint v9.0.0-alpha.0. We anticipate a final v9.0.0 release in the spring of 2024.

Other changes

Deprecation of formatting rules - in a significant shift from ESLint’s roots, we decided to officially deprecate formatting rules
Changes to rule API - for those who write their own rules, we announced important changes to the rule API that will prepare ESLint for our next step: language plugins.

Updates to support the latest ECMAScript features

The team spends much of the year anticipating new ECMAScript features and updating ESLint accordingly. 2023 was an outlier in that most of the changes weren’t syntax-related, and so there wasn’t a lot of additional work. The most significant syntax change, hashbang comments, is something that ESLint already handled to support Node.js.

Financials review

The next few sections dig into the project financials. All of this information is gathered from the Open Collective transaction list with the exception of Tidelift payments (which are retrieved from Tidelift directly). Because transactions come in all throughout the course of a day, we decided to consider transactions beginning on January 1, 2023 at midnight UTC and ending on December 31, 2023 at 11:59 UTC as our fiscal 2023.

Income review

During 2023, ESLint received $180,646.53 USD from all of our income sources. You can see the breakdown of our income sources in the following table.

Source	Amount
Open Collective	$118,381.30
GitHub Sponsors	$25,190.89
Tidelift	$30,077.84
Carbon Ads	$6,380.89
Thanks.dev	$524.61
Stackaid.us	$91.00
Total	$180,646.53

As usual, most of our donations came through Open Collective. Notably, our website ad revenue dropped roughly 50% from 2022, following an overall softening of the display ad business. We’ll be looking at options to improve our website ad revenue in 2024.

The newer sponsoring options, Thanks.dev and Stackaid.us, didn’t provide much income but are both interesting ideas that we’ll keep participating in.

We are grateful to the companies and individuals who generously donated to support ESLint. We know that there has been a lot of turbulence in the tech industry in the past year, and we really appreciate everyone who still decided to sponsor ESLint.

Top sponsors

While we are grateful to all of our sponsors, both large and small, we feel especially grateful to those who donated $1,000 USD or more during 2023. These folks totaled $127,377.42 USD during 2023, representing 70% of our total income.

Sponsor	2023 Donation Total
Chrome Frameworks Fund	$24,000.00
Automattic	$24,000.00
Salesforce	$12,000.00
Airbnb	$12,000.00
Indeed	$10,000.00
Liftoff	$6,000.00
Cybozu	$4,976.00
Sentry	$4,624.00
American Express	$4,467.74
RIDI	$4,000.00
ThemeIsle	$2,400.00
Icons8	$2,400.00
Discord	$2,400.00
Anagram Solver	$2,400.00
Ignition	$2,400.00
HeroCoders	$2,400.00
Transloadit	$2,309.68
Nx (by Nrwl)	$1,800.00
QuickBooks Tool hub	$1,600.00
Yannick Croissant	$1,200.00

Expenses review

In 2023, we spent $185,646.98 USD on the ESLint project as a whole. This includes regular maintenance and development as well as other costs related to the project. See the table below for an overview.

Category	Amount
Maintenance and Development	-$66,910.37
TSC Stipend (Tidelift)	-$30,077.84
Triage and Support	-$10,307.78
Technical Writing	-$8,155.00
Contributor Pool	-$4,500.00
Health Insurance	-$13,447.41
Open Source Collective Fee	-$9,206.88
Ecosystem/Dependencies	-$24,400.00
Community Management	-$15,599.84
Payment Processor Fee	-$2,854.51
Google Workspace	-$187.35
Total	-$185,646.98

As a reminder, the Contributor Pool is money we award for contributions to people who are not on the ESLint team as a way to thank them for making impactful contributions to the project. Community Management refers to the ongoing work required to manage the ESLint Community GitHub organization.

You may notice that our expenses exceeded our income in 2023. Thankfully, we keep a large reserve fund so we can handle any unexpected expenses and to hedge against loss of sponsorships.

Supporting our dependencies and ecosystem

In 2023, the ESLint project donated $24,400.00 USD to ecosystem projects and our dependencies (listed in the previous table as “Ecosystem/Dependencies”). This is part of our ongoing commitment to supporting projects that are important to ESLint.

Project	Donations
typescript-eslint	-$11,800.00
Ajv	-$1,800.00
debug	-$1,800.00
eslint-plugin-import	-$1,800.00
jsx-eslint	-$1,800.00
lint-staged	-$1,800.00
Rollup	-$1,800.00
Sindre Sorhus	-$1,800.00
Total	-$24,400.00

Looking forward to 2024

Once v9.0.0 is released, we’ll be in a good spot to finish work on language plugins and then move on to the complete rewrite we talked about in 2023. It’s hard to believe ESLint is heading into its 11th year, and we’re making the preparations to ensure the project will continue to be useful to the JavaScript community for the next decade.

We know that ESLint is an important part of your toolchain and we appreciate your ongoing support as our team of volunteers moves the project forward.

ESLint v9.0.0-beta.0 released

2024-02-09T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-beta.0 --save-dev

Migration Guide

New default values for rule options

In v9.0.0, the following rules have new defaults:

no-unused-vars: The default value of the caughtErrors option is changed from "none" to "all".
no-useless-computed-key: The default value of the enforceForClassMembers option is changed from false to true.

Stricter `RuleTester` validations

This release adds more checks in RuleTester:

Messages cannot have unsubstituted placeholders.
Suggestions must change the code.
Test case output must be different from code.
Test error objects must specify message or messageId.
Test error object must specify suggestions if the actual error provides suggestions.
Test suggestion objects must specify desc or messageId.
Test suggestion objects must specify output.
filename and only properties of test objects must be of the expected type (string and boolean, respectively).

New API `loadESLint()`

Breaking Changes

9163646 feat!: Rule Tester checks for missing placeholder data in the message (#18073) (fnx)
3c4d51d feat!: default for enforceForClassMembers in no-useless-computed-key (#18054) (Francesco Trotta)
47e60f8 feat!: Stricter rule test validations (#17654) (fnx)
1a94589 feat!: no-unused-vars default caughtErrors to ‘all’ (#18043) (Josh Goldberg ✨)

Features

53f0f47 feat: Add loadESLint() API method for v9 (#18097) (Nicholas C. Zakas)
2d11d46 feat: add suggestions to use-isnan in binary expressions (#17996) (StyleShit)

Bug Fixes

c4d26fd fix: use-isnan doesn’t report on SequenceExpressions (#18059) (StyleShit)

Documentation

f1c7e6f docs: Switch to Ethical Ads (#18090) (Strek)
15c143f docs: JS Foundation -> OpenJS Foundation in PR template (#18092) (Nicholas C. Zakas)
6ea339e docs: add stricter rule test validations to v9 migration guide (#18085) (Milos Djermanovic)
3c816f1 docs: use relative link from CLI to core concepts (#18083) (Milos Djermanovic)
9458735 docs: fix malformed eslint config comments in rule examples (#18078) (Francesco Trotta)
07a1ada docs: link from --fix CLI doc to the relevant core concept (#18080) (Bryan Mishkin)
b844324 docs: Update team responsibilities (#18048) (Nicholas C. Zakas)
aadfb60 docs: document languageOptions and other v9 changes for context (#18074) (fnx)
857e242 docs: tweak explanation for meta.docs rule properties (#18057) (Bryan Mishkin)
10485e8 docs: recommend messageId over message for reporting rule violations (#18050) (Bryan Mishkin)
98b5ab4 docs: Update README (GitHub Actions Bot)
505fbf4 docs: update no-restricted-imports rule (#18015) (Tanuj Kanti)
c25b4af docs: Update README (GitHub Actions Bot)

Chores

e40d1d7 chore: upgrade @eslint/js@9.0.0-beta.0 (#18108) (Milos Djermanovic)
9870f93 chore: package.json update for @eslint/js release (Jenkins)
2c62e79 chore: upgrade @eslint/eslintrc@3.0.1 (#18107) (Milos Djermanovic)
81f0294 chore: upgrade espree@10.0.1 (#18106) (Milos Djermanovic)
5e2b292 chore: upgrade eslint-visitor-keys@4.0.0 (#18105) (Milos Djermanovic)
ce838ad chore: replace dependency npm-run-all with npm-run-all2 ^5.0.0 (#18045) (renovate[bot])
54df731 chore: update dependency markdownlint-cli to ^0.39.0 (#18084) (renovate[bot])
8f06a60 chore: update dependency shelljs to ^0.8.5 (#18079) (Francesco Trotta)
93ffe30 chore: update dependency file-entry-cache to v8 (#17903) (renovate[bot])

ESLint v9.0.0-alpha.2 released

2024-01-26T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-alpha.2 --save-dev

Migration Guide

`no-restricted-imports` configuration improvements

In v8.x, if multiple entries in the paths array of your configuration for the no-restricted-imports rule had the same name property, only the last one would apply. In v9.0.0, all entries apply, allowing for specifying different error messages for different imported names.

`RuleTester` checks for duplicate tests

As of v9.0.0, RuleTester detects and reports duplicate test cases.

Breaking Changes

57089cb feat!: no-restricted-imports allow multiple config entries for same path (#18021) (Milos Djermanovic)
2e1d549 feat!: detect duplicate test cases (#17955) (Bryan Mishkin)

Features

26093c7 feat: fix false negatives in no-this-before-super (#17762) (Yosuke Ota)
5471e43 feat: convert unsafe autofixes to suggestions in no-implicit-coercion (#17985) (Gürgün Dayıoğlu)
e3051be feat: emit warning when .eslintignore file is detected (#17952) (Nitin Kumar)

Bug Fixes

39076fb fix: handle absolute file paths in RuleTester (#17989) (Nitin Kumar)

Documentation

33d1ab0 docs: add more examples to flat config ignores docs (#18020) (Milos Djermanovic)
e6eebca docs: Update sort-keys options properties count (#18025) (LB (Ben Johnston))
1fedfd2 docs: Improve flat config ignores docs (#17997) (Nicholas C. Zakas)
38b9b06 docs: update valid-typeof rule (#18001) (Tanuj Kanti)
b4abfea docs: Update note about ECMAScript support (#17991) (Francesco Trotta)
6788873 docs: Update release blog post template (#17994) (Nicholas C. Zakas)
1f37442 docs: Add sections on non-npm plugin configuration (#17984) (Nicholas C. Zakas)

Chores

6ffdcbb chore: upgrade @eslint/js@9.0.0-alpha.2 (#18038) (Milos Djermanovic)
2c12715 chore: package.json update for @eslint/js release (Jenkins)
cc74c4d chore: upgrade espree@10.0.0 (#18037) (Milos Djermanovic)
dfb68b6 chore: use Node.js 20 for docs sites (#18026) (Milos Djermanovic)
8c1b8dd test: add more tests for ignoring files and directories (#18018) (Milos Djermanovic)
60b966b chore: update dependency @eslint/js to v9.0.0-alpha.1 (#18014) (renovate[bot])
c893bc0 chore: update markdownlint to v0.33.0 (#17995) (Nitin Kumar)

ESLint v9.0.0-alpha.1 released

2024-01-12T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-alpha.1 --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

`no-inner-declarations` new default behavior

In v8.x, no-inner-declarations would flag any functions defined inside of blocks as errors because this behavior was undefined in early versions of JavaScript. As of ES 2015, block-scoped function declarations are well-defined and so we changed the default behavior to not warn on block-scoped functions.

`no-misleading-character-class` now highlights the offending characters

In v8.x, the no-misleading-character-class rule would highlight an entire regular expression if it contained a misleading character class. In v9.0.0, this rule now highlights just the offending characters to help you more easily find errors.

`no-unused-vars` `varsIgnorePattern` option change

The varsIgnorePattern option of no-unused-vars was incorrectly applied to caught error variables in catch conditions. In v9.0.0, varsIgnorePattern no longer applies to caught error variables.

New rule: `no-useless-assignment`

ESLint v9.0.0 introduces a new rule, no-useless-assignment, that is designed to catch situations where you’ve assigned a value to a variable and that value is never used. For example:

let id = 1234;      // 1234 is never used
id = calculateId();

The `--output-file` flag now guarantees a file is output

Better scope analysis

In v9.0.0, we updated the behavior of eslint-scope to fix a couple of longstanding bugs:

Previously, ESLint would treat ("use strict") as a strict mode directive even though it is not. We fixed the behavior so only valid strict mode directives are honored.
The containing scope of a class extends clause was incorrectly set to be the scope containing the class when it should have been the class scope itself. This has been fixed.

`CodePath#currentSegments` removed

As announced in our previous post, CodePath#currentSegments has been removed from the rules API. Please refer to the post for more details.

Breaking Changes

701f1af feat!: no-inner-declaration new default behaviour and option (#17885) (Tanuj Kanti)
bde5105 fix!: handle --output-file for empty output when saving to disk (#17957) (Nitin Kumar)
07107a5 fix!: upgrade eslint-scope@8.0.0 (#17942) (Milos Djermanovic)
3ee0f6c fix!: no-unused-vars varsIgnorePattern behavior with catch arguments (#17932) (Tanuj Kanti)
51f8bc8 fix!: configuration comments with just severity should retain options (#17945) (Milos Djermanovic)
d191bdd feat!: Remove CodePath#currentSegments (#17936) (Milos Djermanovic)

Features

a630edd feat: maintain latest ecma version in ESLint (#17958) (Milos Djermanovic)
b4e0503 feat: add no-useless-assignment rule (#17625) (Yosuke Ota)
287c4b7 feat: no-misleading-character-class granular errors (#17515) (Josh Goldberg ✨)

Bug Fixes

6d11f3d fix: Ensure config keys are printed for config errors (#17980) (Nicholas C. Zakas)
806f708 fix: no-misleading-character-class edge cases with granular errors (#17970) (Milos Djermanovic)

Documentation

96307da docs: migration guide entry for no-inner-declarations (#17977) (Tanuj Kanti)
40be60e docs: Update README (GitHub Actions Bot)
d31c180 docs: fix number of code-path events on custom rules page (#17969) (Richard Hunter)
1529ab2 docs: reorder entries in v9 migration guide (#17967) (Milos Djermanovic)
9507525 docs: Explain how to combine configs (#17947) (Nicholas C. Zakas)
7c78576 docs: Add more removed context methods to migrate to v9 guide (#17951) (Milos Djermanovic)
3a877d6 docs: Update removed CLI flags migration (#17939) (Nicholas C. Zakas)
4a9cd1e docs: Update Linter API for v9 (#17937) (Milos Djermanovic)
2a8eea8 docs: update docs for v9.0.0-alpha.0 (#17929) (Milos Djermanovic)

c2bf27d build: update docs files when publishing prereleases (#17940) (Milos Djermanovic)

Chores

c5e50ee chore: package.json update for @eslint/js release (Jenkins)
1bf2520 chore: Split Docs CI from core CI (#17897) (Nicholas C. Zakas)
320787e chore: delete relative-module-resolver.js (#17981) (Francesco Trotta)
4926f33 refactor: use Object.hasOwn() (#17948) (Milos Djermanovic)
df200e1 refactor: use Array.prototype.at() to get last elements (#17949) (Milos Djermanovic)
750b8df chore: update dependency glob to v10 (#17917) (renovate[bot])
74794f5 chore: removed unused eslintrc modules (#17938) (Milos Djermanovic)
10ed29c chore: remove unused dependency rimraf (#17934) (Francesco Trotta)
903ee60 ci: use --force flag when installing eslint (#17921) (Milos Djermanovic)

ESLint v9.0.0-alpha.0 released

2023-12-29T00:00:00Z

Highlights

This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you having any problems or feedback by creating issues on our GitHub repo.

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide. There are summaries of the significant changes below. (Less significant changes are included in the migration guide.)

This prerelease version of ESLint has a separate documentation section.

Node.js < v18.18.0, v19 no longer supported

As of this post, Node.js v20.x is the LTS release, and as such we are dropping support for all versions of Node.js prior to v18.18.0 as well as v19.x.

Flat config is now the default and has some changes

This release introduces support for eslint.config.mjs and eslint.config.cjs in addition to eslint.config.js, making it easier to use the module format you’d prefer regardless of the module format of the containing package.

This change affects users, plugin developers, and integrators as many aspects of ESLint had to change to make this happen. Please see our previous blog post for more details.

Removed all formatters except `stylish`, `html`, `json`, and `json-with-meta`

The following formatters have been removed:

checkstyle
compact
jslint-xml
junit
tap
unix
visualstudio

If you are using these formatters currently, you’ll need to install the standalone packages for use with ESLint v9.0.0.

Removed `valid-jsdoc` and `require-jsdoc` rules

We have removed valid-jsdoc and require-jsdoc. We recommend using the eslint-plugin-jsdoc plugin instead.

Removed deprecated methods on `context` and `SourceCode`

As we announced in September, we have removed a lot of deprecated methods from context and replaced them with methods on SourceCode.

Updating `eslint:recommended`

The eslint:recommended configuration is updated to include new rules that we feel are important, and to remove deprecated and less important rules.

Changes to how you write rules

We’ve made multiple changes to help prevent errors in rules:

Function-style rules will stop working in v9.0.0. Function-style rules are rules created by exporting a function from a file rather than exporting an object with a create() method.
When a rule doesn’t have meta.schema specified, a default schema of [] will be applied. This means that rules without a schema will be assumed to have no options, which in turn means that validation will fail if options are provided.
RuleTester now strictly checks that suggestion messages are unique for the same lint problem and ensures that suggestions generate valid syntax.

`--quiet` option is more performant

The --quiet option hides all warnings in the ESLint console. In v9.0.0, we are making a performance improvement by also not executing any rules set to "warn".

Running `eslint` with no file arguments

Unused disable directives cause warnings by default

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@9.0.0-alpha.0 --save-dev

Breaking Changes

946ae00 feat!: FlatRuleTester -> RuleTester (#17922) (Nicholas C. Zakas)
baff28c feat!: remove no-inner-declarations from eslint:recommended (#17920) (Milos Djermanovic)
cadfbcd feat!: Rename FlatESLint to ESLint (#17914) (Nicholas C. Zakas)
d1018fc feat!: skip running warnings in --quiet mode (#17274) (Maddy Miller)
fb81b1c feat!: Set default schema: [], drop support for function-style rules (#17792) (Milos Djermanovic)
0b21e1f feat!: add two more cases to no-implicit-coercion (#17832) (Gürgün Dayıoğlu)
2916c63 feat!: Switch Linter to flat config by default (#17851) (Nicholas C. Zakas)
200518e fix!: Parsing ‘exported’ comment using parseListConfig (#17675) (amondev)
bdd6ba1 feat!: Remove valid-jsdoc and require-jsdoc (#17694) (Nicholas C. Zakas)
12be307 fix!: Behavior of CLI when no arguments are passed (#17644) (Nicholas C. Zakas)
8fe8c56 feat!: Update shouldUseFlatConfig and CLI so flat config is default (#17748) (Nicholas C. Zakas)
60dea3e feat!: deprecate no-new-symbol, recommend no-new-native-nonconstructor (#17710) (Francesco Trotta)
5aa9c49 feat!: check for parsing errors in suggestion fixes (#16639) (Bryan Mishkin)
b3e0bb0 feat!: assert suggestion messages are unique in rule testers (#17532) (Josh Goldberg ✨)
e563c52 feat!: no-invalid-regexp make allowConstructorFlags case-sensitive (#17533) (Josh Goldberg ✨)
e5f02c7 fix!: no-sequences rule schema correction (#17878) (MHO)
6ee3e9e feat!: Update eslint:recommended configuration (#17716) (Milos Djermanovic)
c2cf85a feat!: drop support for string configurations in flat config array (#17717) (Milos Djermanovic)
c314fd6 feat!: Remove SourceCode#getComments() (#17715) (Milos Djermanovic)
ae78ff1 feat!: Remove deprecated context methods (#17698) (Nicholas C. Zakas)
f71c328 feat!: Swap FlatESLint-ESLint, FlatRuleTester-RuleTester in API (#17823) (Nicholas C. Zakas)
5304da0 feat!: remove formatters except html, json(-with-metadata), and stylish (#17531) (Josh Goldberg ✨)
e1e827f feat!: Require Node.js ^18.18.0 || ^20.9.0 || >=21.1.0 (#17725) (Milos Djermanovic)

Features

8792464 feat: Enable eslint.config.mjs and eslint.config.cjs (#17909) (Nicholas C. Zakas)
24ce927 feat: warn by default for unused disable directives (#17879) (Bryan Mishkin)

Bug Fixes

f182114 fix: deep merge behavior in flat config (#17906) (Francesco Trotta)
b577e8a fix: allow circular references in config (#17752) (Francesco Trotta)

Documentation

7f0ba51 docs: show NEXT in version selectors (#17911) (Milos Djermanovic)
0a7911e docs: add flat config default to v9 migration guide (#17927) (Milos Djermanovic)
94f8065 docs: Add CLI updates to migrate to v9 guide (#17924) (Nicholas C. Zakas)
16187f2 docs: Add exported and string config notes to migrate to v9 guide (#17926) (Nicholas C. Zakas)
3ae50cc docs: Add RuleTester changes to migrate to v9 guide (#17923) (Nicholas C. Zakas)
0831b58 docs: add rule changes to v9 migration guide (#17925) (Milos Djermanovic)
037abfc docs: update API docs (#17919) (Milos Djermanovic)
afc3c03 docs: add function-style and meta.schema changes to v9 migration guide (#17912) (Milos Djermanovic)
1da0723 docs: update eslint:recommended section in Migrate to v9.x (#17908) (Milos Djermanovic)
f55881f docs: remove configuration-files-new (#17907) (Milos Djermanovic)
63ae191 docs: Migrate to v9.0.0 (#17905) (Nicholas C. Zakas)
e708496 docs: Switch to flat config by default (#17840) (Nicholas C. Zakas)
fdf0424 docs: Update Create a Plugin for flat config (#17826) (Nicholas C. Zakas)
e6a91bd docs: Switch shareable config docs to use flat config (#17827) (Nicholas C. Zakas)
3831fb7 docs: updated examples of max-lines rule (#17898) (Tanuj Kanti)
cd1ac20 docs: Update README (GitHub Actions Bot)

Chores

17fedc1 chore: upgrade @eslint/js@9.0.0-alpha.0 (#17928) (Milos Djermanovic)
cb89ef3 chore: package.json update for @eslint/js release (Jenkins)
f6f4a45 chore: drop structuredClone polyfill for v9 (#17915) (Kevin Gibbons)
412dcbb chore: upgrade eslint-plugin-n@16.6.0 (#17916) (Milos Djermanovic)
02a8baf chore: Rename files with underscores (#17910) (Nicholas C. Zakas)
c0f5d91 chore: remove creating an unused instance of Linter in tests (#17902) (Milos Djermanovic)
3826cdf chore: use jsdoc/no-multi-asterisks with allowWhitespace: true (#17900) (Percy Ma)
a9a17b3 chore: fix getting scope in tests (#17899) (Milos Djermanovic)
595a1f6 test: ensure that CLI tests run with FlatESLint (#17884) (Francesco Trotta)
c7eca43 chore: update dependency markdownlint-cli to ^0.38.0 (#17865) (renovate[bot])
cc0c9f7 ci: bump github/codeql-action from 2 to 3 (#17873) (dependabot[bot])

ESLint v8.56.0 released

2023-12-15T00:00:00Z

Highlights

New features for reporting unused disable directives

The ESLint CLI has a new option --report-unused-disable-directives-severity. This option is available in both eslintrc and flat config modes.
The linterOptions.reportUnusedDisableDirectives configuration option can now be set to a severity value: "error" (or 2), "warn" (or 1), "off" (or 0). This feature is available only in flat config files (eslint.config.js).

Features

0dd9704 feat: Support custom severity when reporting unused disable directives (#17212) (Bryan Mishkin)
31a7e3f feat: fix no-restricted-properties false negatives with unknown objects (#17818) (Arka Pratim Chaudhuri)

Bug Fixes

7d5e5f6 fix: TypeError: fs.exists is not a function on read-only file system (#17846) (Francesco Trotta)
74739c8 fix: suggestion with invalid syntax in no-promise-executor-return rule (#17812) (Bryan Mishkin)

Documentation

9007719 docs: update link in ways-to-extend (#17839) (Amel SELMANE)
3a22236 docs: Update README (GitHub Actions Bot)
54c3ca6 docs: fix migration-guide example (#17829) (Tanuj Kanti)
4391b71 docs: check config comments in rule examples (#17815) (Francesco Trotta)
fd28363 docs: remove mention about ESLint stylistic rules in readme (#17810) (Zwyx)
48ed5a6 docs: Update README (GitHub Actions Bot)

Chores

ba6af85 chore: upgrade @eslint/js@8.56.0 (#17864) (Milos Djermanovic)
60a531a chore: package.json update for @eslint/js release (Jenkins)
ba87a06 chore: update dependency markdownlint to ^0.32.0 (#17783) (renovate[bot])
9271d10 chore: add GitHub issue template for docs issues (#17845) (Josh Goldberg ✨)
70a686b chore: Convert rule tests to FlatRuleTester (#17819) (Nicholas C. Zakas)
f3a599d chore: upgrade eslint-plugin-unicorn to v49.0.0 (#17837) (唯然)
905d4b7 chore: upgrade eslint-plugin-eslint-plugin v5.2.1 (#17838) (唯然)
4d7c3ce chore: update eslint-plugin-n v16.4.0 (#17836) (唯然)
fd0c60c ci: unpin Node.js 21.2.0 (#17821) (Francesco Trotta)

ESLint v8.55.0 released

2023-12-01T00:00:00Z

Highlights

The no-restricted-imports rule has a new option importNamePattern.

Features

8c9e6c1 feat: importNamePattern option in no-restricted-imports (#17721) (Tanuj Kanti)

Documentation

83ece2a docs: fix typo --rules -> --rule (#17806) (OKURA Masafumi)
fffca5c docs: remove “Open in Playground” buttons for removed rules (#17791) (Francesco Trotta)
a6d9442 docs: fix correct/incorrect examples of rules (#17789) (Tanuj Kanti)
383e999 docs: update and fix examples for no-unused-vars (#17788) (Tanuj Kanti)
5a8efd5 docs: add specific stylistic rule for each deprecated rule (#17778) (Etienne)

Chores

eb8950c chore: upgrade @eslint/js@8.55.0 (#17811) (Milos Djermanovic)
93df384 chore: package.json update for @eslint/js release (Jenkins)
fe4b954 chore: upgrade @eslint/eslintrc@2.1.4 (#17799) (Milos Djermanovic)
bd8911d ci: pin Node.js 21.2.0 (#17809) (Milos Djermanovic)
b29a16b chore: fix several cli tests to run in the intended flat config mode (#17797) (Milos Djermanovic)
de165c1 chore: remove unused config-extends fixtures (#17781) (Milos Djermanovic)
d4304b8 chore: remove formatting/stylistic rules from new rule templates (#17780) (Francesco Trotta)
21024fe chore: check rule examples for syntax errors (#17718) (Francesco Trotta)

ESLint v8.54.0 released

2023-11-17T00:00:00Z

Highlights

The no-console rule now provides suggestions for some of the problems reported by this rule.

Features

a7a883b feat: for-direction rule add check for condition in reverse order (#17755) (Angelo Annunziata)
1452dc9 feat: Add suggestions to no-console (#17680) (Joel Mathew Koshy)
21ebf8a feat: update no-array-constructor rule (#17711) (Francesco Trotta)

Bug Fixes

98926e6 fix: Ensure that extra data is not accidentally stored in the cache file (#17760) (Milos Djermanovic)
e8cf9f6 fix: Make dark scroll bar in dark theme (#17753) (Pavel)
3cbeaad fix: Use cwd constructor option as config basePath in Linter (#17705) (Milos Djermanovic)

Documentation

becfdd3 docs: Make clear when rules are removed (#17728) (Nicholas C. Zakas)
05d6e99 docs: update “Submit a Pull Request” page (#17712) (Francesco Trotta)
eb2279e docs: display info about deprecated rules (#17749) (Percy Ma)
d245326 docs: Correct working in migrating plugin docs (#17722) (Filip Tammergård)

Chores

d644de9 chore: upgrade @eslint/js@8.54.0 (#17773) (Milos Djermanovic)
1e6e314 chore: package.json update for @eslint/js release (Jenkins)
6fb8805 chore: Fixed grammar in issue_templates/rule_change (#17770) (Joel Mathew Koshy)
85db724 chore: upgrade markdownlint to 0.31.1 (#17754) (Nitin Kumar)
6d470d2 chore: update dependency recast to ^0.23.0 (#17736) (renovate[bot])
b7121b5 chore: update dependency markdownlint-cli to ^0.37.0 (#17735) (renovate[bot])
633b9a1 chore: update dependency regenerator-runtime to ^0.14.0 (#17739) (renovate[bot])
acac16f chore: update dependency vite-plugin-commonjs to ^0.10.0 (#17740) (renovate[bot])
ba8ca7e chore: add .github/renovate.json5 (#17567) (Josh Goldberg ✨)

What's coming in ESLint v9.0.0

2023-11-07T00:00:00Z

Last month, the Technical Steering Committee (TSC) met to finalize the features for ESLint v9.0.0. This post outlines our plans for v9.0.0. You can keep up to date everything that is planned for v9.0.0 on our project board.

Development plan

Due to the large number of breaking changes planned for v9.0.0, we have decided to develop this release in two phases:

Alpha. The alpha release will be comprised primarily of the changes we believe will cause the most disruption for existing users. Getting these changes into a release early will allow us to gather feedback to ensure things are going as planned.
Beta. The beta release will be comprised of the remaining tasks and smaller breaking changes that will have fewer impacted users.

The specific details about each phase are listed below in this post. Note that if tasks scheduled for the beta are completed in the alpha timeframe, then they will be published in the alpha release.

After the beta has been validated, we will publish one or more release candidates as we continue to fix bugs and deal with compatibility issues.

Significant changes in v9.0.0-alpha

The following changes are planned for the alpha release and represent significant breaking changes.

Flat config now the default and has some changes

Flat config will be the default configuration format for ESLint beginning in v9.0.0 and eslintrc will be deprecated but will still work. To continue using a eslintrc configuration file, you’ll need to set the ESLINT_USE_FLAT_CONFIG environment variable to false. We announced the details in my previous blog post.

We will also remove the "eslint:recommended" and "eslint:all" configuration strings from flat config. In the initial version of flat config, we let you put these directly into the config array, but in v9.0.0, you’ll need to use the corresponding configs from the @eslint/js package.

Dropping support for Node.js < v18.18.0, v19

As of this post, Node.js v20.x is the LTS release, and as such we are dropping support for all versions of Node.js prior to v18.18.0 as well as v19.x.

Removing all formatters except `stylish`, `html`, `json`, and `json-with-meta`

In an ongoing effort to reduce the install size of ESLint, we have decided to remove most of the formatters from the core of ESLint. The formatters being removed are:

checkstyle
compact
jslint-xml
junit
tap
unix
visualstudio

If you are using these formatters currently, you’ll need to install the standalone packages for use with ESLint v9.0.0.

Removing `valid-jsdoc` and `require-jsdoc` rules

Continuing with our theme of reducing ESLint’s install size, we have decided to remove the valid-jsdoc and require-jsdoc rules. These rules have been deprecated since ESLint v5.10.0 and removing them allows us to remove another dependency (doctrine). We recommend using the eslint-plugin-jsdoc plugin instead.

Removing deprecated methods on `context` and `SourceCode`

As we announced in September, we will be removing a lot of deprecated methods from context and replacing them with methods on SourceCode. Please read the above mentioned post for more details on these changes.

Additionally, we will be removing the deprecated SourceCode#getComments() method.

Updating `eslint:recommended`

The eslint:recommended configuration will be updated to include new rules that we feel are important, and to remove deprecated rules.

Changes to how you write rules

To clean up and make rules easier to work with, we’re making two changes:

Function-style rules will stop working in v9.0.0. Function-style rules are rules created by exporting a function from a file rather than exporting an object with a create() method.
When a rule doesn’t have meta.schema specified, a default schema of [] will be applied. This means that rules without a schema will be assumed to have no options, which in turn means that validation will fail if options are provided.

You can read more about this change in the RFC.

`--quiet` option is more performant

The --quiet option hides all warnings in the ESLint console. In v9.0.0, we are making a performance improvement by also not executing any rules set to "warn". You can read more about this change in the RFC.

Running `eslint` with no file arguments

Starting in v9.0.0, if you are using flat config and you don’t pass any file arguments to the CLI, the CLI will default to linting the current directory, which means you can type npx eslint and it will just work.

For eslintrc, missing file arguments will result in an error.

Significant changes in v9.0.0-beta

The following changes are planned for the beta release and represent significant breaking changes.

Removing `CodePath#currentSegments`

In order to move forward with the language plugins work, we’ll be removing CodePath#currentSegments. This only affects rules that are using code path analysis. You can read more in the previous blog post.

Configuration comments with just severity now only override severity

Due to a bug in the way inline configuration comments were handled, comments such as /*eslint no-undef: warn */ would automatically remove any options set for the corresponding rule in a configuration file. In v9.0.0, these types of comments will only change the severity of the rule and will not affect any other options.

New `no-new-native-nonconstructor` rule replaces `no-new-symbol`

The no-new-symbol rule was designed to prevent new Symbol() in your code, which is an error because Symbol isn’t a constructor. There are other global functions that also don’t have constructors, so we decided to create a new rule, no-new-native-nonconstructor, to cover all of those cases. This new rule will be added to eslint:recommended and no-new-symbol will be deprecated.

Changes to `RuleTester`

The RuleTester class will be updated to catch more problems with rules:

There will be a failure if multiple suggestion fixers have the same message.
There will be a failure if a suggestion contains a parsing error.
Several additional assertions will be added to catch invalid or buggy test cases.

When to expect ESLint v9.0.0

We expect the first alpha release of ESLint v9.0.0 to be released in December or January, depending on the progress we make on our tasks. At that point, we will gather feedback from the community and fix any outstanding issues that make it difficult for people to upgrade. We hope to the beta release a couple of months after the alpha, and the final release a couple of months after that. Availability of all releases will be announced on this blog, on our X account, and on our Mastodon account, so please stay tuned!

ESLint v8.53.0 released

2023-11-03T00:00:00Z

Highlights

Core formatting rules have been deprecated. Please see Deprecation of formatting rules blog post for more details.

Features

528e1c0 feat: Deprecate formatting rules (#17696) (Nicholas C. Zakas)
c0b11dd feat: Add suggestions for no-prototype-builtins (#17677) (Yonathan Randolph)

Bug Fixes

1ad6257 fix: ensure that exit code for fatal errors is not overwritten (#17683) (Milos Djermanovic)
b329ea7 fix: add ; after JSX nodes in no-object-constructor autofix (#17672) (Francesco Trotta)

Documentation

ab8c60d docs: change position of return to top button (#17688) (Tanuj Kanti)
4fc44c0 docs: update twitter icon to new X icon (#17687) (Tanuj Kanti)
4164b2c docs: Update README (GitHub Actions Bot)
8651895 docs: Fix tabs in rule examples (#17653) (Francesco Trotta)
3aec1c5 docs: explained rule fixers and suggestions (#17657) (Josh Goldberg ✨)

Chores

ba4d4d5 chore: remove metascraper (#17707) (Milos Djermanovic)
0d07338 chore: Update dependencies (#17706) (Milos Djermanovic)
93256a3 chore: package.json update for @eslint/js release (ESLint Jenkins)
485ec7d test: fix ESLint tests for caching (#17699) (Milos Djermanovic)
db06a7f ci: bump actions/setup-node from 3 to 4 (#17676) (dependabot[bot])
994596b ci: run tests in Node.js 21 (#17673) (Francesco Trotta)

Deprecation of formatting rules

2023-10-26T00:00:00Z

In ESLint v8.53.0, scheduled to be released on Friday, November 3, 2023, we will formally deprecate our formatting rules. Formatting rules are those rules that simply enforce code conventions around spacing, semicolons, string formats, etc. For a variety of reasons, which are discussed in this post, this is the right decision for ESLint going forward. However, to understand how we got here, it’s helpful to look backward for a moment.

Background

When ESLint was initially released in 2013, the JavaScript ecosystem was embroiled in a debate about whether or not source code formatting should be part of a linter. JSLint, the original JavaScript linter, heavily encoded its author’s formatting preferences into the tool. Those preferences were carried over and loosened a bit in JSLint’s successor, JSHint, but by 2013, JSHint had announced that it was deprecating its formatting options and would be removing them in the next major release. While the options were never removed, they still show this warning:

Warning This option has been deprecated and will be removed in the next major release of JSHint.

JSHint is limiting its scope to issues of code correctness. If you would like to enforce rules relating to code style, check out the JSCS project.

The JSCS project was born to cater to the growing desire of JavaScript developers to format their code in more specific ways. Appearing in the same year as ESLint, there was a bit of an experimentation period as people tried using different combinations of JSHint, JSCS, and ESLint to achieve their linting and formatting needs.

Early on, I thought the only way for ESLint to reasonably compete with JSHint was to ensure that all available JSHint rules had ESLint equivalents. While the strength of ESLint was (and still is) in creating custom rules, I didn’t think ESLint would get much adoption if everyone had to recreate the JSHint rules for themselves. My initial plan was to make a couple dozen core rules and then leave the rest to be implemented as plugins.

As time went on, ESLint received more and more requests to add formatting and stylistic rules to the core. Many of the requests mentioned that they didn’t want to use two tools (ESLint and JSCS) on their code and if ESLint could do everything that JSCS did, they could drop JSCS and just use ESLint. And so, now that ESLint had a team, we focused on getting feature parity to support this use case. Eventually, we did such a good job that JSCS usage dropped and we merged JSCS into ESLint.

What we didn’t know at the time was that JSHint had the right idea, and although ESLint had become the dominant linter (and source code formatter) for JavaScript, we had also signed up for a lot of work.

JavaScript’s explosion and the maintenance burden

In the ensuing years, and especially spurred on by ECMAScript 6 and the growth of React, the way people were writing JavaScript was changing dramatically. Increasingly popular style guides like Airbnb and Standard encouraged JavaScript developers to get more specific about how their code was written. As a result, ESLint was inundated with requests for exceptions and options on formatting rules. Over the last ten years, we’ve seen all manner of bizarre styles accompanied by requests to enforce them in ESLint core rules. And every time new syntax is introduced, we get a flurry of requests to update existing rules and implement new rules.

As we approached 300 rules in the core, we tried to reduce the maintenance burden by freezing stylistic rules so that we were no longer chasing down corner cases to support everyone’s personal preferences. That helped somewhat, but not enough.

Rule clashes. People expect that core rules will play nice with each other, meaning that no two rules should flag the same problem nor will any two core rules give conflicting advice. While that was easy when there were less than 30 core rules, with 300 rules it became difficult, if not impossible, to achieve.
Unrealistic expectations. With a large core of formatting rules, users expected that every possible style guide should be achievable just with core rules and without involving plugins. This put more pressure on the team to continue adding options, which also increased the size of the core.
Effort vs. value misalignment. The maintenance burden of continuously adding new options and exceptions to support everyone’s style guides was falling on the ESLint team whereas the value was being extracted by a small number of users.
Opportunity cost. The more time we had to spend maintaining formatting rules, the less time we had to spend on things that are beneficial to large numbers of our users.
Lack of interest. While ESLint benefits from outside contributions, those contributors are just not interested to chasing down corner cases of spacing. The ESLint team, itself, prioritized these rules much lower than any other work, which often left issues open for extended periods of time.
Consistency issues. Because ESLint’s rules are designed to be atomic and not to have access to other rules, we would run into issues where it wasn’t possible to correctly fix an error because the information was in another rule. For example, if an autofix needs to add a new line of code, it would need to know how the file is indented in order to apply the correct fix. However, the indent rule controls indenting for ESLint, which meant that other rules needed to apply fixes without indentation and then trust that the indent rule would fix the indentation on a subsequent pass.

All of these problems continued to grow as ESLint got older, and we’re finally at a point where we just cannot keep up with them.

The deprecated rules

The following list contains all of the rules that will be deprecated in v8.53.0:

All of these rules will be deprecated as of the next release, but will not be removed until at least ESLint v10.0.0 (if not later). You can continue to use them although you may see deprecation warnings in the ESLint CLI.

What you should do instead

We recommend using a source code formatter instead of ESLint for formatting your code. Source code formatters are built to understand the entire file and apply consistent formatting throughout. While you might not have as much control over exceptions as with ESLint, the tradeoff is the simplicity and speed you’ll get vs. configuring ESLint with dozens of individual rules. There are two formatters that we recommend:

Prettier - a JavaScript-based formatter with support for formatting a large number of languages
dprint - a Rust-based formatter with support for a smaller set of languages

If the idea of using a dedicated source code formatter doesn’t appeal to you, you can also use @stylistic/eslint-plugin-js for JavaScript or @stylistic/eslint-plugin-ts for TypeScript. These packages contain the deprecated formatting rules from the ESLint core and typescript-eslint, respectively. The packages are maintained by Anthony Fu, who has decided to continue maintaining these rules going forward. If you’d like to continue using the rules mentioned in this post, then we recommend switching to these packages.

Conclusion

We know that a lot of people rely on ESLint for code quality and formatting purposes, and as such, we don’t take significant decisions like this lightly. Unfortunately, the way we’ve been doing things just won’t scale much further and we needed to make this change. The ubiquity and popularity of dedicated source code formatters made this decision somewhat easier, as was Anthony Fu volunteering to maintain the rules as a separate package. We hope that one of the available options mentioned in this post will ensure that people can continue formatting their source code in their preferred way.

ESLint v8.52.0 released

2023-10-20T00:00:00Z

Highlights

Unused `eslint-enable` directives

The CLI option --report-unused-disable-directives and the config option reportUnusedDisableDirectives:true now also report and autofix unused eslint-enable directives. An eslint-enable directive is considered unused if it doesn’t match with any eslint-disable directives, meaning that it doesn’t re-enable any rules.

/* eslint-disable no-console */

console.log("hello");

/* eslint-enable no-continue -- this directive is unused */

Features

70648ee feat: report-unused-disable-directive to report unused eslint-enable (#17611) (Yosuke Ota)

Bug Fixes

5de9637 fix: Ensure shared references in rule configs are separated (#17666) (Nicholas C. Zakas)
dcfe573 fix: add preceding semicolon in suggestions of no-object-constructor (#17649) (Francesco Trotta)

Documentation

476d58a docs: Add note about invalid CLI flags when using flat config. (#17664) (Nicholas C. Zakas)
660ed3a docs: Plugin flat config migration guide (#17640) (Nicholas C. Zakas)
a58aa20 docs: fix examples for several rules (#17645) (Milos Djermanovic)
179929b docs: Remove trailing newline from the code of Playground links (#17641) (Francesco Trotta)
f8e5c30 docs: Update README (GitHub Actions Bot)
b7ef2f3 docs: Enable pretty code formatter output (#17635) (Nicholas C. Zakas)
0bcb9a8 docs: Fix syntax errors in rule examples (#17633) (Francesco Trotta)
61b9083 docs: Make no-continue example code work (#17643) (Zhongyuan Zhou)
9fafe45 docs: upgrade to 11ty 2.0 (#17632) (Percy Ma)
ff8e4bf docs: Update README (GitHub Actions Bot)
fab249a docs: Update README (GitHub Actions Bot)
392305b docs: Update no-irregular-whitespace and fix examples (#17626) (Francesco Trotta)
6b8acfb docs: Add real whitespace to no-trailing-spaces examples (#17630) (Francesco Trotta)
1000187 docs: Fix examples in unicode-bom (#17631) (Francesco Trotta)
000290c docs: Update README (GitHub Actions Bot)

Chores

6d1f0c2 chore: upgrade @eslint/js@8.52.0 (#17671) (Milos Djermanovic)
d63d4fe chore: package.json update for @eslint/js release (ESLint Jenkins)
f30cefe test: fix FlatESLint tests for caching (#17658) (Milos Djermanovic)
ef650cb test: update tests for no-promise-executor-return (#17661) (Milos Djermanovic)

Flat config rollout plans

2023-10-10T00:00:00Z

It may seem hard to believe, but the RFC for ESLint’s new configuration system, nicknamed flat config, was first written in 2019. It took until 2022 (v8.21.0) for us to release an experimental, opt-in version of flat config. Since then, we’ve been making changes and improvements based on feedback from the community. The plan was always to allow the current configuration system, nicknamed eslintrc, to exist alongside flat config for a period of time to allow a smooth transition for ESLint users. With flat config now feature complete, we are happy to share the rollout plan.

Flat config by default in ESLint v9.0.0

When ESLint v9.0.0 is released, either the end of this year or beginning of next year, flat config will be the default configuration system and we will deprecate, but not remove, eslintrc. New features will be added only for flat config, so we encourage everyone to move off of eslintrc as quickly as possible to take advantage of everything v9.0.0 will offer.

What this change means for you depends on how you use ESLint, and if you have any questions or concerns, please stop by our Discord to discuss with the team.

For CLI users, this means a few things:

The ESLint CLI will search for eslint.config.js by default instead of a .eslintrc.* file.
If an eslint.config.js file is not found, the CLI will consider this an error and won’t run.
If you want to use eslintrc, you’ll need to set the ESLINT_USE_FLAT_CONFIG environment variable to false. When you do this, you’ll get a deprecation warning in the console.

For rule developers, the RuleTester class will be equivalent to the current FlatRuleTester class. If you are passing any parser-related options to your rule tests, you’ll need to update those to comply with the flat config format for those options.

You should also make sure that your rules aren’t using context.parserOptions and context.parserPath. Instead, you should be using context.languageOptions and context.languageOptions.parser, which also work when ESLint is run in eslintrc mode. See our previous post for more information.

For shareable config authors, you should update your shareable configs to use flat config format. This includes moving referenced plugins from the peerDependencies section of package.json to the dependencies section.

For plugin developers, you should update your exported configs to use flat config format. The rest of your plugin, including rules and processors, don’t require any changes. Please see the plugin migration guide for more details.

For API users, you’ll need to decide whether or not you want to support both configuration systems in the short term. The API in v9.0.0 will change in the following ways:

The ESLint class will now be equivalent to the FlatESLint class in v8.x. With the exception of a few options, this should mostly be a transparent change.
The LegacyESLint class will still be provided to allow access to the eslintrc functionality, but we will not be updating this class in v9.x. All new features will be implemented only for flat config-based APIs.
The FlatESLint class will still be provided to avoid unnecessarily breaking existing implementations, but we encourage you to switch over to ESLint as soon as possible.
The shouldUseFlatConfig() method will return true unless the ESLINT_USE_FLAT_CONFIG environment variable is false.
The Linter class will switch to flat config mode by default, but you’ll still be able to set it to use eslintrc by specifying the configType option in the constructor to be "eslintrc", such as:
```
const linter = new Linter({ configType: "eslintrc" });
```

eslintrc removed in ESLint v10.0.0

When ESLint v10.0.0 is released (end of 2024 or early 2025 in all likelihood), the eslintrc configuration system will be completely removed.

For CLI users, this means a few things:

The ESLint CLI will search for eslint.config.js instead of a .eslintrc.* file.
If an eslint.config.js file is not found, the CLI will consider this an error and won’t run.
The ESLINT_USE_FLAT_CONFIG environment variable will no longer be honored but won’t throw an error.
CLI options that were specific to eslintrc config files will be removed.

For rule developers, the context.parserPath and context.parserOptions properties will be removed.

For shareable config authors, there are no additional concerns in v10.0.0.

For plugin developers, there are no additional concerns in v10.0.0.

For API users, you’ll need to stop using the classes from the /use-at-your-own-risk entrypoint. The API in v10.0.0 will change in the following ways:

The ESLint class will now be the only way to interact with the core.
The LegacyESLint class will be removed.
The FlatESLint class will be removed.
The shouldUseFlatConfig() method will always return true.
The Linter class configType constructor option will be invalid and throw an error.

Conclusion

We’ve come a long way in the development of our new configuration system and we still have a long way to go. This is an intentionally slow rollout to make sure that everyone can comfortably update their config files with as little disruption as possible. Shifting an entire ecosystem over to a new API is a responsibility we take seriously, and we hope that is evident in the phased rollout plan. You can continue to follow our progress by watching the implementation issue. If you need help with, or have questions about, any of what was discussed in this post, please start a discussion or stop by Discord to talk with the team.

ESLint v8.51.0 released

2023-10-06T00:00:00Z

Highlights

New CLI option `--no-warn-ignored`

This release includes a new CLI option --no-warn-ignored that, when on, suppresses warnings about ignored files that were explicitly passed in the file list. The new option is available only in the flat config mode.

This option is particularly useful when ESLint is run with --max-warnings 0 from tools that pass a list of individual files, such as lint-staged, as it prevents exit code 1 when an ignored file is passed.

{
    "lint-staged": {
        "*.js": "eslint --max-warnings 0 --no-warn-ignored"
    }
}

API

As part of this change, FlatESLint constructor has a new option warnIgnored: boolean, default true.

The warnIgnored option of FlatESLint#lintText() is still available, but it now defaults to the value of the constructor option. Effectively, its default value is changed from false to true. In order to retain previous behavior, pass warnIgnored: false to FlatESLint#lintText():

const eslint = new FlatESLint();

await eslint.lintFiles(patterns);
await eslint.lintText(code, { filePath, warnIgnored: false });

Features

0a9c433 feat: Add --no-warn-ignored CLI option for flat config (#17569) (Domantas Petrauskas)
977e67e feat: logical-assignment-operators to report expressions with 3 operands (#17600) (Yosuke Ota)

Bug Fixes

f976b2f fix: make rule severity case-sensitive in flat config (#17619) (Milos Djermanovic)
0edfe36 fix: Ensure crash error messages are not duplicated (#17584) (Nicholas C. Zakas)
dd79abc fix: eslint-disable to be able to parse quoted rule names (#17612) (Yosuke Ota)
d2f6801 fix: Ensure correct code path for && followed by ?? (#17618) (Nicholas C. Zakas)

Documentation

ee5be81 docs: default to sourceType: "module" in rule examples (#17615) (Francesco Trotta)
1aa26df docs: Add more examples for multiline-ternary (#17610) (George Ashiotis)
47d0b44 docs: Update README (GitHub Actions Bot)
dbf831e docs: use generated og image (#17601) (Percy Ma)
1866da5 docs: Update README (GitHub Actions Bot)

Chores

1ef39ea chore: upgrade @eslint/js@8.51.0 (#17624) (Milos Djermanovic)
f8c7403 chore: package.json update for @eslint/js release (ESLint Jenkins)
2665552 test: fix flat config linter tests to use Linter in flat config mode (#17616) (Milos Djermanovic)
7b77bcc chore: Refactor CodePathState (#17510) (Nicholas C. Zakas)
bc77c9a chore: Document and refactor ForkContext (#17566) (Nicholas C. Zakas)
24e1f14 chore: Refactor and document CodePath (#17558) (Nicholas C. Zakas)

Preparing your custom rules for ESLint v9.0.0

2023-09-26T00:00:00Z

When ESLint v9.0.0 is released, it will ship with several breaking changes for rule authors. These changes are necessary as part of the work to implement language plugins, which gives ESLint first-class support for linting languages other than JavaScript. We’ve had to make these changes because ESLint has, from the start, assumed that it would only ever be used to lint JavaScript. As such, there wasn’t a lot of thought put into where methods that rules used to interact with source code should live. When revisiting the API for the language plugins work we found that the inconsistencies we were able to live with in a JavaScript-only world will not work in a language-agnostic ESLint core.

Automatically update your rules

Before explaining all of the changes introduced in ESLint v9.0.0, it’s helpful to know that most of the changes described in this post can be automatically made using the eslint-transforms utility. To use the utility, first install it and then run the v9-rule-migration transform, like this:

# install the utility
npm install eslint-transforms -g

# apply the transform to one file
eslint-transforms v9-rule-migration rule.js

# apply the transform to all files in a directory
eslint-transforms v9-rule-migration rules/

Not every change can be addressed with eslint-tranforms, though, so below is a complete list of the API changes and recommended ways to address them.

`context` methods becoming properties

As we look towards the API we’d like rules for other languages to have, we decided to convert some methods on context to properties. The methods in the following table just returned some data that didn’t change, so there was no reason they couldn’t be properties instead.

Deprecated on `context`	Property on `context`
`context.getSourceCode()`	`context.sourceCode`
`context.getFilename()`	`context.filename`
`context.getPhysicalFilename()`	`context.physicalFilename`
`context.getCwd()`	`context.cwd`

We are deprecating the methods in favor of the properties (added in v8.40.0). These methods will be removed in v10.0.0 (not v9.0.0) as they are not blocking language plugins work. Here’s an example that ensures the correct value is used:

module.exports = {
    create(context) {

        const sourceCode = context.sourceCode ?? context.getSourceCode();
        const cwd = context.cwd ?? context.getCwd();
        const filename = context.filename ?? context.getFilename();
        const physicalFilename = context.physicalFilename ?? context.getPhysicalFilename();

        return {
            Program(node) {
                // do something
            }
        }
    }
};

From `context` to `SourceCode`

The majority of the breaking changes for rule authors consist of moving methods off of the context object that is passed into rules and onto the SourceCode object that is retrieved via context.sourceCode (or the deprecated context.getSourceCode(); see below). The area of responsibility for context vs. SourceCode has shifted during the lifetime of ESLint: In the beginning, context was the home for everything rules needed to use. Once we added SourceCode, we slowly started adding more methods to it. The end result was that some methods lived on context and some methods lived on SourceCode, and the only reason why? The time at which the methods were added.

In a language-agnostic ESLint core, we need to redefine the responsibilities of these two objects. Going forward, context is the home for functionality that rules need to interact with the core while SourceCode is the home for functionality that rules need to interact with the code being linted. This allows the same context object to be used regardless of the language being linted as well as allowing language plugins to define their own SourceCode class to provide methods that are unique to that language.

All of this is to say that we are deprecating all of the code-related methods on context and moving them to SourceCode. The following table shows which fields on context are moving to SourceCode. Note that the method signatures remain unchanged for all of these methods even if the name changes:

Deprecated on `context`	Replacement(s) on `SourceCode`
`context.getSource()`	`sourceCode.getText()`
`context.getSourceLines()`	`sourceCode.getLines()`
`context.getAllComments()`	`sourceCode.getAllComments()`
`context.getNodeByRangeIndex()`	`sourceCode.getNodeByRangeIndex()`
`context.getComments()`	`sourceCode.getCommentsBefore()`, `sourceCode.getCommentsAfter()`, `sourceCode.getCommentsInside()`
`context.getCommentsBefore()`	`sourceCode.getCommentsBefore()`
`context.getCommentsAfter()`	`sourceCode.getCommentsAfter()`
`context.getCommentsInside()`	`sourceCode.getCommentsInside()`
`context.getJSDocComment()`	`sourceCode.getJSDocComment()`
`context.getFirstToken()`	`sourceCode.getFirstToken()`
`context.getFirstTokens()`	`sourceCode.getFirstTokens()`
`context.getLastToken()`	`sourceCode.getLastToken()`
`context.getLastTokens()`	`sourceCode.getLastTokens()`
`context.getTokenAfter()`	`sourceCode.getTokenAfter()`
`context.getTokenBefore()`	`sourceCode.getTokenBefore()`
`context.getTokenByRangeStart()`	`sourceCode.getTokenByRangeStart()`
`context.getTokens()`	`sourceCode.getTokens()`
`context.getTokensAfter()`	`sourceCode.getTokensAfter()`
`context.getTokensBefore()`	`sourceCode.getTokensBefore()`
`context.getTokensBetween()`	`sourceCode.getTokensBetween()`
`context.parserServices`	`sourceCode.parserServices`

All of the context methods listed in this table will be removed in ESLint v9.0.0, and the replacement methods on SourceCode have already been in place for six years, so you should have no problem switching to the new methods. (Yes, we deprecated these and then completely forgot to remove them.)

In addition to the methods in this table, there are several other methods that are also moving but required different method signatures.

`context.getScope()`

The context.getScope() method is used to retrieve a scope object for the currently-traversed node. This method was always a bit strange because it uses ESLint’s internal traversal state to determine which node to use as a reference point to retrieve a scope object. That meant it was both limited, because you couldn’t change the reference node, and confusing, because it wasn’t always clear what node was being referenced. So, we are deprecating this method and will remove it in ESLint v9.0.0.

We have introduced a new SourceCode#getScope(node) method that requires you to pass in the reference node. This method was added in ESLint v8.37.0 so it has already been in place for the last six months. For best compatibility, you can check for the presence of this new method to determine which one to use:

module.exports = {
    create(context) {

        const sourceCode = context.sourceCode ?? context.getSourceCode();

        return {
            Program(node) {
                const scope = sourceCode.getScope
                    ? sourceCode.getScope(node)
                    : context.getScope();

                // do something with scope
            }
        }
    }
};

`context.getAncestors()`

The context.getAncestors() method is another method on context that uses the internal traversal state to return the ancestors of the currently visited node. Also similar to context.getScope(), this meant the method was both limited and unclear. We are deprecating this method and will remove it in v9.0.0. The replacement method is SourceCode#getAncestors(node) (added in v8.38.0), which requires you to pass in the node whose ancestors you want to retrieve. Here is an example that checks for the correct method to use:

module.exports = {
    create(context) {

        const sourceCode = context.sourceCode ?? context.getSourceCode();

        return {
            Program(node) {
                const ancestors = sourceCode.getAncestors
                    ? sourceCode.getAncestors(node)
                    : context.getAncestors();

                // do something with ancestors
            }
        }
    }
};

`context.getDeclaredVariables(node)`

The context.getDeclaredVariables(node) returns all variables declared by the given node (such as in a let statement). We are deprecating this method and will remove it in v9.0.0. We are replacing it with SourceCode#getDeclaredVariables(node) (added in v8.38.0), which works exactly the same way. Here is an example that checks for the correct method to use:

module.exports = {
    create(context) {

        const sourceCode = context.sourceCode ?? context.getSourceCode();

        return {
            Program(node) {
                const variables = sourceCode.getDeclaredVariables
                    ? sourceCode.getDeclaredVariables(node)
                    : context.getDeclaredVariables(node);

                // do something with variables
            }
        }
    }
};

`context.markVariableAsUsed(name)`

The context.markVariableAsUsed(name) method finds a variable with the given name in the current scope and marks it as used so it won’t cause a violation in the no-unused-vars rule. This method has quite a bit of magic going on behind the scenes, as it uses the currently visited node in the traversal to retrieve a scope and then searches that scope for a variable with the given name. We are deprecating this method and will remove it in v9.0.0. The replacement method is SourceCode#markVariableAsUsed(name, node) (added in v8.39.0) and requires you to pass in the reference node for the scope to search. (The scope ends up being the same as calling SourceCode#getScope(node).) Here is an example that checks for the correct method to use:

module.exports = {
    create(context) {

        const sourceCode = context.sourceCode ?? context.getSourceCode();

        return {
            Program(node) {
                const result = sourceCode.markVariableAsUsed
                    ? sourceCode.markVariableAsUsed("foo", node)
                    : context.markVariableAsUsed("foo");

                if (result) {
                  // the variable was found and marked as used
                }
            }
        }
    }
};

`CodePath#currentSegments`

A little-known ability of ESLint rules is analyzing code paths. ESLint core rules use code path analysis in multiple rules to validate not just what the code looks like but also how the logic flows. This is done through accessing CodePath and CodePathSegment objects. In doing our research for language plugins, we discovered that CodePath#currentSegments actually represents another traversal state that is exposed in rules. Specifically, CodePath#currentSegments is an array that grows and shrinks throughout traversal as you encounter different code path segments. Because code path analysis is unique to JavaScript, we can’t have the core tracking this traversal state any longer. After evaluating several options, we decided that having an object that represented both code path data and traversal state was undesirable, so we are deprecating CodePath#currentSegments and will remove it in v9.0.0. We needed to add two new event handlers, onUnreachableCodePathSegmentStart and onUnreachableCodePathSegmentEnd, to allow access to the same data (these were added in v8.49.0).

To recreate this data, you’ll need to track the traversal state manually, which can be accomplished with the following code:

module.exports = {
    meta: {
        // ...
    },
    create(context) {

        // tracks the code path we are currently in
        let currentCodePath;

        // tracks the segments we've traversed in the current code path
        let currentSegments;

        // tracks all current segments for all open paths
        const allCurrentSegments = [];

        return {

            onCodePathStart(codePath) {
                currentCodePath = codePath;
                allCurrentSegments.push(currentSegments);
                currentSegments = new Set();
            },

            onCodePathEnd(codePath) {
                currentCodePath = codePath.upper;
                currentSegments = allCurrentSegments.pop();
            },

            onCodePathSegmentStart(segment) {
                currentSegments.add(segment);
            },

            onCodePathSegmentEnd(segment) {
                currentSegments.delete(segment);
            },

            onUnreachableCodePathSegmentStart(segment) {
                currentSegments.add(segment);
            },

            onUnreachableCodePathSegmentEnd(segment) {
                currentSegments.delete(segment);
            }
        };

    }
};

We have already made this change in all of the ESLint core rules to validate that the approach works as expected.

`context` properties: `parserOptions` and `parserPath` being removed

Additionally, the context.parserOptions and context.parserPath properties are deprecated and will be removed in v10.0.0 (not v9.0.0). There is a new context.languageOptions property that allows rules to access similar data as context.parserOptions. In general, though, rules should not depend on information either in context.parserOptions or context.languageOptions to determine how they should behave.

The context.parserPath property was intended to allow rules to retrieve an instance of the parser that ESLint is using via require(). However, the new flat config system does not know the location of the parser module to load, so we are unable to provide this data. Further, because the JavaScript ecosystem is moving to ESM, any value returned from this property will not work with import(). This property was added early on in ESLint’s life and we generally recommend that rules not try to further parse JavaScript code inside of them. If necessary, you can use context.languageOptions.parser to access the parser ESLint is using.

Conclusion

ESLint has been around for ten years, and in that time, we have collected some API cruft that we need to clean up in order to prepare ESLint for the next ten years. The API changes described in this post are a necessary step towards enabling ESLint to lint non-JavaScript languages and to better separate core functionality from language-specific functionality. The team spent a lot of time planning this transition point in ESLint’s lifecycle and we hope that these changes are just a small inconvenience for the ecosystem. If you need help with, or have questions about, any of what was discussed in this post, please start a discussion or stop by Discord to talk with the team.

Update (2024-06-06): Added section on eslint-tranforms.

ESLint v8.50.0 released

2023-09-22T00:00:00Z

Highlights

The no-new-object rule has been deprecated in favor of the new no-object-constructor rule.
The array-callback-return rule has a new option allowVoid.

Features

27d5a9e feat: add suggestions to array-callback-return (#17590) (Tanuj Kanti)
f9082ff feat: flat-rule-tester make sure default config always matches (#17585) (fnx)
83914ad feat: Implement SourceCode#applyInlineConfig() (#17351) (Nicholas C. Zakas)
22a5582 feat: add rule no-object-constructor, deprecate no-new-object (#17576) (Francesco Trotta)
85a3d9e feat: allowVoid option in array-callback-return (#17564) (Tanuj Kanti)

Bug Fixes

cc4d26b fix: Ensure deprecated context.parserServices warns (#17593) (Nicholas C. Zakas)
1ea4cfb fix: Ensure all RuleTester tests all deprecated context methods (#17587) (Nicholas C. Zakas)
aa1b657 fix: wrong suggestion and message in no-misleading-character-class (#17571) (Yosuke Ota)

Documentation

1800537 docs: Fix and standardize JSX code examples (#17591) (Francesco Trotta)
48a44a7 docs: Add correct/incorrect tags to prefer-arrow-callback (#17589) (Francesco Trotta)
20893d4 docs: fix incorrect tag’s place (#17575) (Tanuj Kanti)
bd7a71f docs: Update README (GitHub Actions Bot)

Chores

f8a8a2d chore: upgrade @eslint/js@8.50.0 (#17599) (Milos Djermanovic)
38ada6d chore: package.json update for @eslint/js release (ESLint Jenkins)

ESLint v8.49.0 released

2023-09-08T00:00:00Z

Highlights

Code path analysis now provides two new events that can be used in rules: onUnreachableCodePathSegmentStart and onUnreachableCodePathSegmentEnd.
CodePath#currentSegments property has been deprecated and will be removed in ESLint v9. If you use this property in your custom rules, please refer to code path analysis usage examples for how to update your code.
The lines-between-class-members rule has a new option enforce that allows for more granular configurations.

Features

da09f4e feat: Implement onUnreachableCodePathStart/End (#17511) (Nicholas C. Zakas)
32b2327 feat: Emit deprecation warnings in RuleTester (#17527) (Nicholas C. Zakas)
acb7df3 feat: add new enforce option to lines-between-class-members (#17462) (Nitin Kumar)

Documentation

ecfb54f docs: Update README (GitHub Actions Bot)
de86b3b docs: update no-promise-executor-return examples (#17529) (Nitin Kumar)
032c4b1 docs: add typescript template (#17500) (James)
cd7da5c docs: Update README (GitHub Actions Bot)

Chores

b7621c3 chore: remove browser test from npm test (#17550) (Milos Djermanovic)
cac45d0 chore: upgrade @eslint/js@8.49.0 (#17549) (Milos Djermanovic)
cd39508 chore: package.json update for @eslint/js release (ESLint Jenkins)
203a971 ci: bump actions/checkout from 3 to 4 (#17530) (dependabot[bot])
a40fa50 chore: use eslint-plugin-jsdoc’s flat config (#17516) (Milos Djermanovic)
926a286 test: replace Karma with Webdriver.IO (#17126) (Christian Bromann)
f591d2c chore: Upgrade config-array (#17512) (Nicholas C. Zakas)

ESLint v8.48.0 released

2023-08-25T00:00:00Z

Highlights

The no-promise-executor-return rule has a new option allowVoid.

Features

1fbb3b0 feat: correct update direction in for-direction (#17483) (Francesco Trotta)
d73fbf2 feat: rule tester do not create empty valid or invalid test suites (#17475) (fnx)
ee2f718 feat: Allow void in rule no-promise-executor-return (#17282) (nopeless)

Bug Fixes

7234f6a fix: update RuleTester JSDoc and deprecations (#17496) (Jonas Berlin)

Documentation

7a51d77 docs: no-param-reassign mention strict mode (#17494) (Stephen Hardy)
9cd7ac2 docs: add fetch script to package.json conventions (#17459) (Nitin Kumar)
cab21e6 docs: advice for inline disabling of rules (#17458) (Ashish Yadav)
056499d docs: fix example of flat config from plugin (#17482) (Francesco Trotta)
9e9edf9 docs: update documentation URL in error message (#17465) (Nitin Kumar)

Chores

8dd3cec chore: upgrade @eslint/js@8.48.0 (#17501) (Milos Djermanovic)
6d0496e chore: package.json update for @eslint/js release (ESLint Jenkins)
9d4216d chore: Refactor and document CodePathSegment (#17474) (Nicholas C. Zakas)

ESLint v8.47.0 released

2023-08-11T00:00:00Z

Features

53d7508 feat: update regex for methods with thisArg (#17439) (Francesco Trotta)

Bug Fixes

631648e fix: do not report on shadowed constructors in no-new-wrappers (#17447) (Francesco Trotta)

Documentation

a766a48 docs: document lack of config file names (#17442) (James)
a1635d6 docs: Update README (GitHub Actions Bot)
47a0859 docs: update [require-unicode-regexp](/docs/rules/require-unicode-regexp).md as following up #17402 (#17441) (SUZUKI Sosuke)
fcdc85d docs: Update README (GitHub Actions Bot)
2a92b6c docs: update with “Specifying Parser Options” (#17435) (Cheol-Won)
d743ed3 docs: add metadata for parser/processor (#17438) (Huáng Jùnliàng)
224376c docs: Update README (GitHub Actions Bot)
a41a8e4 docs: update script names in README (#17432) (Nitin Kumar)

Chores

bf69aa6 chore: Update dependencies (#17456) (Nicholas C. Zakas)
0e45760 chore: package.json update for @eslint/js release (ESLint Jenkins)
757bfe1 chore: Remove add-to-triage (#17450) (Nicholas C. Zakas)
b066640 chore: standardize npm script names (#17431) (Nitin Kumar)
6b2410f chore: Update add-to-triage.yml (#17444) (Nicholas C. Zakas)

ESLint v8.46.0 released

2023-07-28T00:00:00Z

Highlights

Support for regular expressions `v` flag

We have updated ESLint to fully support the ECMAScript 2024 regular expression v flag. This flag allows more complex operations such as difference/subtraction, intersection, and nested character classes. These updates include parsing and ensuring that rules related to regular expressions are behaving as expected.

Better error messages for flat config

As we continue to work on flat config, we received some feedback that the error messages were a bit difficult to understand when an eslintrc config was accidentally used. We added more explicit checking for eslintrc-style configs to output more useful error messages that include links to the relevant documentation.

Features

8a93438 feat: require-unicode-regexp support v flag (#17402) (SUZUKI Sosuke)
1a2f966 feat: no-useless-escape support v flag (#17420) (Yosuke Ota)
ee68d1d feat: no-empty-character-class support v flag (#17419) (Milos Djermanovic)
853d32b feat: deprecate no-return-await (#17417) (Carlos Lopez)
d4f02e4 feat: no-control-regex support v flag (#17405) (Yosuke Ota)
2a35f3e feat: prefer-named-capture-group support v flag (#17409) (Yosuke Ota)
8ca8b50 feat: Better error message for flat config plugins (#17399) (Nicholas C. Zakas)
509f753 feat: no-misleading-character-class support v flag (#17406) (Yosuke Ota)
3caf514 feat: no-regex-spaces support v flag (#17407) (Yosuke Ota)
b7fad2b feat: prefer-regex-literals support v flag (#17410) (Yosuke Ota)
a6a3ad4 feat: no-useless-backreference support v flag (#17408) (Yosuke Ota)
94954a7 feat: no-invalid-regexp support v flag (#17404) (Yosuke Ota)
1af6eac feat: adds option for allowing empty object patterns as parameter (#17365) (Tanuj Kanti)
cf03104 feat: Improve config error messages (#17385) (Nicholas C. Zakas)

Bug Fixes

9803c7c fix: FlatESLint#getRulesMetaForResults shouldn’t throw on unknown rules (#17393) (Milos Djermanovic)
42faa17 fix: Update no-loop-func to not overlap with no-undef (#17358) (Matt Wilkinson)

Documentation

4d474e3 docs: update with TypeScript info (#17423) (James)
091f44e docs: File extension named processor deprecation (#17362) (Matt Wilkinson)
9254a6c docs: Update README (GitHub Actions Bot)
6d6dc51 docs: fix overlapping of open in playground button (#17403) (Tanuj Kanti)
7fc3a2c docs: Add private class features info to no-underscore-dangle (#17386) (Matt Wilkinson)
da73e58 docs: Migrating eslint-env configuration comments (#17390) (Francesco Trotta)
80dffed docs: fix Ignoring Files section in config migration guide (#17392) (Milos Djermanovic)
8a9abb7 docs: Update README (GitHub Actions Bot)
7e9be4b docs: Update README (GitHub Actions Bot)
0b0bbe0 docs: Update README (GitHub Actions Bot)

Chores

d1eb7e4 chore: Update ecosystem dependencies (#17427) (Nicholas C. Zakas)
fab9e97 chore: package.json update for eslint-config-eslint release (ESLint Jenkins)
6246711 chore: package.json update for @eslint/js release (ESLint Jenkins)
0aa0bc3 chore: Add PRs to triage project (#17421) (Nicholas C. Zakas)

ESLint v8.45.0 released

2023-07-14T00:00:00Z

Highlights

Here are some of the important changes in this release.

Exporting of new `LegacyESLint` class

As we continue our transition to the flat config system, we’ve been working with integrators to understand how best to help them transition as well. While we provided the FlatESLint class to allow integrations to start using the flat config system before it’s set to default, we discovered that our original plan (replace ESLint with FlatESLint in v9.0.0) would have left integrations unable to support eslintrc during the transition.

To fix this, we added the LegacyESLint class as an export from /use-at-your-own-risk. Both FlatESLint and LegacyESLint will be available through the v9.0.0 lifecycle, allowing integrators to continue to support both config formats. You can use these classes like this:

const { FlatESLint, LegacyESLint } = require("eslint/use-at-your-own-risk");

If you are using the ESLint class in your integration, it’s a good idea to switch that to LegacyESLint to make the upgrade to v9.0.0 as smooth as possible when it is released later this year.

The plan is to remove both FlatESLint and LegacyESLint classes in v10.0.0.

New configuration migration guide

We’ve published a new Configuration Migration Guide to help you make the switch from eslintrc to flat config formats. Flat config is now considered feature complete and it’s a good time to start switching over before flat config becomes the default in v9.0.0. This guide walks you through the various sections of your eslintrc file and shows how to convert them to flat config.

We’re grateful for the early adopters of the new config system who provided the feedback that makes up the core of this new guide.

Features

cdd063c feat: Expose LegacyESLint in unsupported API (#17341) (Nicholas C. Zakas)
d34abe5 feat: fix indent rule for else-if (#17318) (Milos Djermanovic)

Bug Fixes

b79b6fb fix: Fix suggestion message in no-useless-escape (#17339) (Francesco Trotta)
c667055 fix: provide unique fix and fix.range objects in lint messages (#17332) (Milos Djermanovic)

Documentation

89f3225 docs: add playground links to correct and incorrect code blocks (#17306) (Josh Goldberg ✨)
f8892b5 docs: Expand rule option schema docs (#17198) (Matt Wilkinson)
8bcbf11 docs: Config Migration Guide (#17230) (Ben Perlmutter)
bb30908 docs: Update README (GitHub Actions Bot)
84d243b docs: Update README (GitHub Actions Bot)
b762632 docs: Update README (GitHub Actions Bot)
138c096 docs: add more prefer-destructuring examples with array destructuring (#17330) (Milos Djermanovic)
1fc50a8 docs: max-len rule code and tabWidth as positional arguments (#17331) (Jesús Leganés-Combarro)

Chores

68f63d7 chore: package.json update for @eslint/js release (ESLint Jenkins)
5ca9b4d chore: update eslint-config-eslint exports (#17336) (Milos Djermanovic)
7bf2e86 chore: remove unused dependencies (#17352) (Percy Ma)
c6f8cd0 chore: Remove defaultIgnores from FlatESLint private members (#17349) (Francesco Trotta)
0052374 chore: move jsdoc settings to eslint-config-eslint (#17338) (唯然)

ESLint v8.44.0 released

2023-06-30T00:00:00Z

Highlights

The no-extra-parens rule has a new option ternaryOperandBinaryExpressions.
eslint.config.js configuration files can now also export a promise that resolves to the configuration array. This can be useful for using ESM dependencies in CommonJS configuration files.
The context.parserServices property is now deprecated in favor of SourceCode#parserServices. This change is part of the implementation of language plugins.
ESLint’s default parser espree now supports RegExp v flag with set notation + properties of strings ES2024 syntax. Please note that the core rules have not yet been updated to support this syntax.

Features

1766771 feat: add es2023 and es2024 environments (#17328) (Milos Djermanovic)
4c50400 feat: add ecmaVersion: 2024, regexp v flag parsing (#17324) (Milos Djermanovic)
4d411e4 feat: add ternaryOperandBinaryExpressions option to no-extra-parens rule (#17270) (Percy Ma)
c8b1f4d feat: Move parserServices to SourceCode (#17311) (Milos Djermanovic)
ef6e24e feat: treat unknown nodes as having the lowest precedence (#17302) (Brad Zacher)
1866e1d feat: allow flat config files to export a Promise (#17301) (Milos Djermanovic)

Bug Fixes

a36bcb6 fix: no-unused-vars false positive with logical assignment operators (#17320) (Gweesin Chan)
7620b89 fix: Remove no-unused-labels autofix before potential directives (#17314) (Francesco Trotta)
391ed38 fix: Remove no-extra-semi autofix before potential directives (#17297) (Francesco Trotta)

Documentation

526e911 docs: resubmit pr 17115 doc changes (#17291) (唯然)
e1314bf docs: Integration section and tutorial (#17132) (Ben Perlmutter)
19a8c5d docs: Update README (GitHub Actions Bot)

Chores

49e46ed chore: upgrade @eslint/js@8.44.0 (#17329) (Milos Djermanovic)
a1cb642 chore: package.json update for @eslint/js release (ESLint Jenkins)
840a264 test: More test cases for no-case-declarations (#17315) (Elian Cordoba)
e6e74f9 chore: package.json update for eslint-config-eslint release (ESLint Jenkins)
eb3d794 chore: upgrade semver@7.5.3 (#17323) (Ziyad El Abid)
cf88439 chore: upgrade optionator@0.9.3 (#17319) (Milos Djermanovic)
9718a97 refactor: remove unnecessary code in flat-eslint.js (#17308) (Milos Djermanovic)
f82e56e perf: various performance improvements (#17135) (moonlightaria)
da81e66 chore: update eslint-plugin-jsdoc to 46.2.5 (#17245) (唯然)
b991640 chore: switch eslint-config-eslint to the flat format (#17247) (唯然)

ESLint v8.43.0 released

2023-06-16T00:00:00Z

Highlights

The no-irregular-whitespace rule has a new option skipJSXText.
The ESLint documentation site now provides a Custom Rule Tutorial with step-by-step instructions on how to create and use a custom rule.

Features

14581ff feat: directive prologue detection and autofix condition in quotes (#17284) (Francesco Trotta)
e50fac3 feat: add declaration loc to message in block-scoped-var (#17252) (Milos Djermanovic)
1b7faf0 feat: add skipJSXText option to no-irregular-whitespace rule (#17182) (Azat S)
030a827 Revert “feat: docs license (#17010)” (#17231) (唯然)

Bug Fixes

5338b56 fix: normalize cwd passed to ESLint/FlatESLint constructor (#17277) (Milos Djermanovic)
54383e6 fix: Remove no-extra-parens autofix for potential directives (#17022) (Francesco Trotta)

Documentation

8b855ea docs: resubmit pr17061 doc changes (#17292) (唯然)
372722e docs: resubmit pr17012 doc changes (#17293) (唯然)
67e7af3 docs: resubmit custom-rules doc changes (#17294) (唯然)
9e3d77c docs: Resubmit Fix formatting in Custom Rules docs (#17281) (Milos Djermanovic)
503647a docs: Resubmit markVariableAsUsed docs (#17280) (Nicholas C. Zakas)
e0cf0d8 docs: Custom rule & plugin tutorial (#17024) (Ben Perlmutter)
8e51ea9 docs: resubmit no-new rule documentation (#17264) (Nitin Kumar)
1b217f8 docs: resubmit Custom Processors documentation (#17265) (Nitin Kumar)
428fc76 docs: resubmit Create Plugins documentation (#17268) (Nitin Kumar)
bdca88c docs: resubmit Configuration Files documentation (#17267) (Nitin Kumar)
f5c01f2 docs: resubmit Manage Issues documentation (#17266) (Nitin Kumar)
b199295 docs: Resubmit custom rules update docs (#17273) (Ben Perlmutter)
0e9980c docs: add new omitLastInOneLineClassBody option to the semi rule (#17263) (Nitin Kumar)
cb2560f docs: Resubmit getScope/getDeclaredVariables docs (#17262) (Nicholas C. Zakas)
85d2b30 docs: explain how to include predefined globals (#17261) (Marcus Wyatt)
de4d3c1 docs: update flat config default ignore patterns (#17258) (Milos Djermanovic)
3912f3a docs: Improve ignores documentation (#17239) (Francesco Trotta)
35e11d3 docs: fix typos and missing info (#17257) (Ed Lucas)
0bc257c docs: Clarify no-div-regex rule docs (#17051) (#17255) (Francesco Trotta)
788d836 docs: add references to MIT License (#17248) (Milos Djermanovic)
58aab6b docs: Update README (GitHub Actions Bot)
3ef5814 docs: Revert all changes after the license change (#17227) (Milos Djermanovic)
03fc4aa docs: Update README (GitHub Actions Bot)

Chores

78350f6 chore: upgrade @eslint/js@8.43.0 (#17295) (Milos Djermanovic)
62bf759 chore: package.json update for @eslint/js release (ESLint Jenkins)
e0a2448 chore: docs package.license ISC => MIT (#17254) (唯然)
6a0196c chore: use eslint-plugin-eslint-plugin flat configs (#17204) (Milos Djermanovic)

ESLint v8.42.0 released

2023-06-02T00:00:00Z

Features

b8448ff feat: correct no-useless-return behaviour in try statements (#16996) (Nitin Kumar)

Bug Fixes

a589636 fix: Config with ignores and without files should not always apply (#17181) (Milos Djermanovic)
c4fad17 fix: Correct ignore message for “node_modules” subfolders (#17217) (Francesco Trotta)

Documentation

01d7142 docs: Update README (GitHub Actions Bot)
e5182b7 docs: Update README (GitHub Actions Bot)

Chores

6ca5b7c chore: upgrade @eslint/js@8.42.0 (#17236) (Milos Djermanovic)
67fc5e7 chore: package.json update for @eslint/js release (ESLint Jenkins)
0892412 refactor: remove Identifier listener in no-irregular-whitespace (#17235) (Milos Djermanovic)
f67d298 test: Add FlatESLint tests with missing config files (#17164) (Milos Djermanovic)
5b68d51 chore: Fix fixedsize attribute in code path analysis DOT debug output (#17202) (Milos Djermanovic)
37432f2 chore: update descriptions in key-spacing tests (#17195) (Milos Djermanovic)

ESLint v8.41.0 released

2023-05-19T00:00:00Z

Highlights

Integrations can now use the new function shouldUseFlatConfig() to determine whether to use the FlatESLint class instead of the ESLint class.
The performance of the indent rule has been significantly improved.

Features

880a431 feat: change default ignore pattern to **/node_modules/ in flat config (#17184) (Milos Djermanovic)
8bf5505 feat: expose shouldUseFlatConfig (#17169) (Connor Prussin)

Bug Fixes

4f5440d fix: incorrect warning message for ignored dotfiles (#17196) (Milos Djermanovic)
94da96c fix: unify LintMessage type (#17076) (Brandon Mills)
0c415cd fix: validate ignorePatterns constructor option in FlatESLint class (#17139) (Milos Djermanovic)
9682d66 fix: switch grapheme-splitter to graphemer (#17160) (fisker Cheung)

Documentation

7709b14 docs: Update README (GitHub Actions Bot)
7f183e0 docs: Update triage process description (#17157) (Nicholas C. Zakas)
b68346b docs: fix license to reflect relicensing of jshint (#17165) (Stefan Bischof)

Chores

f43216a chore: upgrade @eslint/js@8.41.0 (#17200) (Milos Djermanovic)
95c3007 chore: package.json update for @eslint/js release (ESLint Jenkins)
ddc5291 chore: don’t use deprecated context methods in ast-utils tests (#17194) (Milos Djermanovic)
b1516db chore: Fix return type of findFlatConfigFile (#17161) (Milos Djermanovic)
918b0fd perf: Store indent descriptors in a plain array (#17148) (Francesco Trotta)
4caa344 refactor: locateConfigFileToUse returns an Error object (#17159) (唯然)

ESLint v8.40.0 released

2023-05-05T00:00:00Z

Highlights

Rules can now use properties context.sourceCode, context.cwd, context.filename, and context.physicalFilename instead of methods context.getSourceCode(), context.getCwd(), context.getFilename(), and context.getPhysicalFilename() respectively. The methods are now considered deprecated.
The FlatESLint class has a new method findConfigFile(). It returns the path to the config file being used by the instance or undefined if no config file is being used.
The semi rule has a new option omitLastInOneLineClassBody.

Features

5db7808 feat: improve flat config errors for invalid rule options and severities (#17140) (Josh Goldberg ✨)
f5574dc feat: Add findConfigFile() method to FlatESLint (#17142) (Nicholas C. Zakas)
e52b98b feat: add sourceCode property to the rule context (#17107) (Nitin Kumar)
1468f5b feat: add physicalFilename property to the rule context (#17111) (Nitin Kumar)
0df4d4f feat: add cwd to rule context (#17106) (Nitin Kumar)
52018f2 feat: add filename property to the rule context (#17108) (Nitin Kumar)
559ff4e feat: add new omitLastInOneLineClassBody option to the semi rule (#17105) (Nitin Kumar)

Bug Fixes

f076e54 fix: Ensure FlatESLint#findConfigFile() doesn’t throw. (#17151) (Nicholas C. Zakas)

Documentation

e980bf3 docs: Update README (GitHub Actions Bot)
e92a6fc docs: Update README (GitHub Actions Bot)
af5fe64 docs: Fix custom rule schema docs (#17115) (Adam Jones)
4a352a9 docs: explain how to include predefined globals (#17114) (Marcus Wyatt)
5ea15d9 docs: add mastodon link in readme (#17110) (唯然)

Chores

4053004 chore: upgrade @eslint/js@8.40.0 (#17156) (Milos Djermanovic)
50fed1d chore: package.json update for @eslint/js release (ESLint Jenkins)
4c7a170 chore: upgrade @eslint/eslintrc@2.0.3 (#17155) (Milos Djermanovic)
e80b7cc chore: upgrade espree@9.5.2 (#17154) (Milos Djermanovic)
ce3ac91 chore: upgrade eslint-visitor-keys@3.4.1 (#17153) (Milos Djermanovic)
9094d79 chore: add latest/ to meta.docs.url in all core rules (#17136) (Milos Djermanovic)
d85efad perf: don’t use grapheme-splitter on ASCII strings in key-spacing rule (#17122) (Milos Djermanovic)

ESLint v8.39.0 released

2023-04-21T00:00:00Z

Highlights

Performance of SourceCode methods that search for comments has been improved following recommendations from a blog post by Marvin Hagemeister. For example, our tests showed that this change reduces linting time for eslint-plugin-jsdoc rules by 6~11%.
The context.markVariableAsUsed(name) method is now deprecated in favor of SourceCode#markVariableAsUsed(name, node). This change is part of the implementation of language plugins.

Features

3f7af9f feat: Implement SourceCode#markVariableAsUsed() (#17086) (Nicholas C. Zakas)

Documentation

6987dc5 docs: Fix formatting in Custom Rules docs (#17097) (Milos Djermanovic)
4ee92e5 docs: Update README (GitHub Actions Bot)
d8e9887 docs: Custom Rules cleanup/expansion (#16906) (Ben Perlmutter)
1fea279 docs: Clarify how to add to tsc agenda (#17084) (Nicholas C. Zakas)
970ef1c docs: Update triage board location (Nicholas C. Zakas)
6d8bffd docs: Update README (GitHub Actions Bot)

Chores

60a6f26 chore: upgrade @eslint/js@8.39.0 (#17102) (Milos Djermanovic)
d5ba5c0 chore: package.json update for @eslint/js release (ESLint Jenkins)
f57eff2 ci: run tests on Node.js v20 (#17093) (Nitin Kumar)
9d1b8fc perf: Binary search in token store utils.search (#17066) (Francesco Trotta)
07a4435 chore: Add request for minimal repro to bug report (#17081) (Nicholas C. Zakas)
eac4943 refactor: remove unnecessary use of SourceCode#getAncestors in rules (#17075) (Milos Djermanovic)
0a7b60a chore: update description of SourceCode#getDeclaredVariables (#17072) (Milos Djermanovic)
6e2df71 chore: remove unnecessary references to the LICENSE file (#17071) (Milos Djermanovic)

ESLint v8.38.0 released

2023-04-07T00:00:00Z

Highlights

Rules can now use SourceCode#getDeclaredVariables(node) and SourceCode#getAncestors(node) methods. These methods work the same as context.getDeclaredVariables(node) and context.getAncestors() respectively, except that SourceCode#getAncestors isn’t limited to the currently traversed node and the node argument is mandatory. context.getDeclaredVariables and context.getAncestors are now considered deprecated in favor of the SourceCode methods. This change is part of the implementation of language plugins.

Features

a1d561d feat: Move getDeclaredVariables and getAncestors to SourceCode (#17059) (Nicholas C. Zakas)

Bug Fixes

1c1ece2 fix: do not report on RegExp(...args) in require-unicode-regexp (#17037) (Francesco Trotta)

Documentation

7162d34 docs: Mention new config system is complete (#17068) (Nicholas C. Zakas)
0fd6bb2 docs: Update README (GitHub Actions Bot)
c83531c docs: Update/remove external links, eg. point to eslint-community (#17061) (Pelle Wessman)
a3aa6f5 docs: Clarify no-div-regex rule docs (#17051) (Francesco Trotta)
b0f11cf docs: Update README (GitHub Actions Bot)
da8d52a docs: Update the second object instance for the “no-new” rule (#17020) (Ahmadou Waly NDIAYE)
518130a docs: switch language based on current path (#16687) (Percy Ma)
24206c4 docs: Update README (GitHub Actions Bot)

Chores

59ed060 chore: upgrade @eslint/js@8.38.0 (#17069) (Milos Djermanovic)
88c0898 chore: package.json update for @eslint/js release (ESLint Jenkins)
cf682d2 refactor: simplify new-parens rule schema (#17060) (MHO)
0dde022 ci: bump actions/add-to-project from 0.4.1 to 0.5.0 (#17055) (dependabot[bot])

ESLint v8.37.0 released

2023-03-28T00:00:00Z

Highlights

Rules can now use SourceCode#getScope(node) to get the scope of the given node. The node argument is mandatory. This method works the same as context.getScope() but isn’t limited to the currently traversed node. The context.getScope() method is now considered deprecated in favor of SourceCode#getScope(node). This change is part of the implementation of language plugins.
Parsers and plugins can now export a meta object with name and version properties to allow for easier debugging and more effective caching. In the new config system, ESLint uses these values when serializing configuration objects (for example, the –print-config CLI option) and when determining whether cached lint results (the --cache CLI option) are still valid. If a parser/plugin provides meta, ESLint can now invalidate caches when a new version of the parser/plugin is installed.
In the new config system, languageOptions.parser must now be a parser object. Referencing parsers by "pluginName/parserName" is no longer supported.
The require-unicode-regexp rule now provides suggestions for some of the problems it reports.

Features

b6ab8b2 feat: require-unicode-regexp add suggestions (#17007) (Josh Goldberg)
10022b1 feat: Copy getScope() to SourceCode (#17004) (Nicholas C. Zakas)
1665c02 feat: Use plugin metadata for flat config serialization (#16992) (Nicholas C. Zakas)
b3634f6 feat: docs license (#17010) (Samuel Roldan)
892e6e5 feat: languageOptions.parser must be an object. (#16985) (Nicholas C. Zakas)

Bug Fixes

619f3fd fix: correctly handle null default config in RuleTester (#17023) (Brad Zacher)
1fbf118 fix: getFirstToken/getLastToken on comment-only node (#16889) (Francesco Trotta)
129e252 fix: Fix typo in logical-assignment-operators rule description (#17000) (Francesco Trotta)

Documentation

75339df docs: fix typos and missing info in id-match docs (#17029) (Ed Lucas)
ec2d830 docs: Fix typos in the semi rule docs (#17012) (Andrii Lundiak)
e39f28d docs: add back to top button (#16979) (Tanuj Kanti)
721c717 docs: Custom Processors cleanup and expansion (#16838) (Ben Perlmutter)
d049f97 docs: ‘How ESLint is Maintained’ page (#16961) (Ben Perlmutter)
5251a92 docs: Describe guard options for guard-for-in (#16986) (alope107)
6157d81 docs: Add example to guard-for-in docs. (#16983) (alope107)
fd47998 docs: update Array.prototype.toSorted specification link (#16982) (Milos Djermanovic)
3e1cf6b docs: Copy edits on Maintain ESLint docs (#16939) (Ben Perlmutter)

Chores

c67f299 chore: upgrade @eslint/js@8.37.0 (#17033) (Milos Djermanovic)
ee9ddbd chore: package.json update for @eslint/js release (ESLint Jenkins)
dddb475 chore: upgrade @eslint/eslintrc@2.0.2 (#17032) (Milos Djermanovic)
522431e chore: upgrade espree@9.5.1 (#17031) (Milos Djermanovic)
f5f9a88 chore: upgrade eslint-visitor-keys@3.4.0 (#17030) (Milos Djermanovic)
4dd8d52 ci: bump actions/stale from 7 to 8 (#17026) (dependabot[bot])
ad9dd6a chore: remove duplicate scss, (#17005) (Strek)
ada6a3e ci: unpin Node 19 (#16993) (Milos Djermanovic)
c3da975 chore: Remove triage label from template (#16990) (Nicholas C. Zakas)
69bc0e2 ci: pin Node 19 to 19.7.0 (#16987) (Milos Djermanovic)

Announcing the ESLint Community GitHub organization

2023-03-21T00:00:00Z

In our 2022 year in review, we briefly mentioned a couple of project kickoffs, and we’re excited to now announce the official eslint-community GitHub organization.

The strength of ESLint is in its ecosystem, and we continue to investigate different ways of further supporting that community. We began by donating to community projects, to ensure that high-value projects were receiving the funds they needed to continue with ongoing maintenance and development. Our next step is to create the eslint-community GitHub organization as a home for high-value projects in the ESLint ecosystem.

About the organization

As you can read in the “eslint-community GitHub organization” RFC, the goal of this new organization is to have a place where community members can help ensure widely depended upon ESLint-related packages live and never fall out of maintenance.
The Community Core team (which currently consists of @aladdin-add, @ota-meshi, @voxpelli and myself @MichaelDeBoey) and all package maintainers will make sure these packages stay up-to-date with newer ESLint releases, and they don’t hold the wider community back by depending on a single person’s GitHub or npm account.

Organization projects

You might have noticed that some of your most beloved ESLint-related packages have already been moved over to or been forked by the new eslint-community organization. A full list of the current projects include:

eslint-formatter-codeframe and eslint-formatter-table
We took these over from @fregante
eslint-plugin-eslint-plugin
@aladdin-add, @bmish and @not-an-aardvark transferred this repo to the new eslint-community organization, but they’re still maintaining it
eslint-plugin-promise
We took this one over from @xjamundx
eslint-plugin-security
We took this one over from the @nodesecurity team, but @nzakas is still maintaining it
eslint-plugin-eslint-comments, eslint-utils and regexpp
We created a fork from @mysticatea’s repos and published them under the @eslint-community npm organization.

We also intend to fork, bring up to date, and publish the following packages originally authored by @mysticatea as well:

eslint-plugin-es
We’ll work on getting all eslint-plugin-es-x features merged as well
eslint-plugin-node
We’ll work on getting all eslint-plugin-n features merged as well

Of course, we don’t want to stop there.

Submitting projects for the organization

If you think your project would be a good fit for the new eslint-community organization, or you’re depending on a project that’s currently unmaintained and want to have the community to adopt it, you can contact the Community Core team on the official ESLint Discord.

Keep in mind that we’ll only be able to accept projects that adhere to the following criteria:

Is it a package that is ESLint-related?
Mostly this will be ESLint plugins, but (unmaintained) dependencies of such packages, closely related packages, or packages split from the main ESLint repo (like eslint-formatter-codeframe or eslint-formatter-table) or used by the main repo (like eslint-utils and regexpp) could go in the eslint-community GitHub organization as well.

We won’t be accepting shareable configs as these are typically very opinionated and are easy to extend when necessary.
Is it widely depended upon throughout the ESLint community?
We don’t have a real number in mind here, but the packages we currently maintain (or that we’re planning to maintain) almost all have at least 3M downloads/week.

These criteria aren’t written in stone, but are the guidelines we’re beginning with to determine whether to accept a project into the organization.

Conclusion

We hope that this new eslint-community organization will help us further support the awesome ESLint ecosystem and ensure that the community can continue to rely on these high-value, widely depended upon projects for years to come. Ensuring that the ESLint ecosystem remains vibrant and without stagnation is a key goal of the project as a whole, and we believe the eslint-community organization will only increase the confidence of ESLint users when relying on community-maintained projects.

If you have any questions about the eslint-community organization, feel free to ask them on the official ESLint Discord.

ESLint v8.36.0 released

2023-03-10T00:00:00Z

Highlights

The multiline-comment-style rule has a new option checkJSDoc. This option can only be used when the string option is set to "separate-lines".

Features

c89a485 feat: Add checkJSDoc option to multiline-comment-style (#16807) (Laurent Cozic)
f5f5e11 feat: Serialize parsers/processors in flat config (#16944) (Nicholas C. Zakas)
4799297 feat: use @eslint-community dependencies (#16784) (Michaël De Boey)

Bug Fixes

92c1943 fix: correctly iterate files matched by glob patterns (#16831) (Nitin Kumar)

Documentation

b98fdd4 docs: Update README (GitHub Actions Bot)
caf08ce docs: fix estree link in custom formatters docs (#16967) (Milos Djermanovic)
3398431 docs: Custom Parsers cleanup/expansion (#16887) (Ben Perlmutter)
19d3531 docs: Update README (GitHub Actions Bot)
b09a512 docs: detect and fix broken links (#16837) (Nitin Kumar)

Chores

602b111 chore: upgrade @eslint/js@8.36.0 (#16978) (Milos Djermanovic)
43c2345 chore: package.json update for @eslint/js release (ESLint Jenkins)
00afb84 chore: upgrade @eslint/eslintrc@2.0.1 (#16977) (Milos Djermanovic)
698c5aa chore: upgrade espree@9.5.0 (#16976) (Milos Djermanovic)
75acdd2 chore: lint more js files in docs (#16964) (Milos Djermanovic)
89d9844 ci: bump actions/add-to-project from 0.4.0 to 0.4.1 (#16943) (dependabot[bot])

ESLint v8.35.0 released

2023-02-26T00:00:00Z

Highlights

ESLint’s predefined recommended and all configs are now exported from a new @eslint/js package. Those using "eslint:recommended" or "eslint:all" as strings in the new flat config format should instead install and import @eslint/js and reference predefined configs as js.configs.recommended or js.configs.all.
The no-constant-binary-expression rule now catches more cases involving the nullish coalescing operator, ??.
A new version of the esquery selector engine includes performance improvements covered in a blog post by Marvin Hagemeister.

Features

8e34a04 feat: add afterHashbangComment option to lines-around-comment rule (#16920) (SUZUKI Sosuke)
c8c0c71 feat: Move all and recommended configs into package. (#16844) (Nicholas C. Zakas)
71f6f0d feat: report more cases with ?? in no-constant-binary-expression (#16826) (Daiki Nishikawa)

Bug Fixes

9698bc5 fix: pin esquery v1.4.0 (fixes #16896) (#16897) (唯然)

Documentation

f9f195e docs: Plugin docs cleanup & expansion (#16862) (Ben Perlmutter)
df809fd docs: Custom Formatters page cleanup/expansion (#16886) (Ben Perlmutter)
0700d1b docs: Add PostCSS/Autoprefixer/CSSNano (#16502) (Nick Schonning)
7b9e9bf docs: support unicode anchors (#16782) (Percy Ma)
5fbc0bf docs: Update README (GitHub Actions Bot)
67865a0 docs: Remove mention of mailing list (#16869) (Amaresh S M)
43af24a docs: Add explanation of when to use ‘warn’ severity (#16882) (Nicholas C. Zakas)
ed2999b docs: Shareable configs page edits and expansion (#16824) (Ben Perlmutter)
2780635 docs: fix typos (#16884) (Lioness100)
5bdaae2 docs: Ways to Extend ESLint page (#16861) (Ben Perlmutter)

Chores

cdcbe12 chore: upgrade @eslint/js@8.35.0 (#16935) (Brandon Mills)
c954c34 chore: package.json update for @eslint/js release (ESLint Jenkins)
5a517da chore: package.json update for @eslint/js release (ESLint Jenkins)
9f10926 chore: upgrade @eslint/eslintrc@2.0.0 (#16928) (Milos Djermanovic)
da728fa ci: use LTS node version in workflows (#16907) (Nitin Kumar)
c57b4f3 perf: upgrade to esquery@1.4.2 (#16901) (Milos Djermanovic)
9122f07 chore: Update stale bot settings (#16870) (Nicholas C. Zakas)

ESLint v8.34.0 released

2023-02-10T00:00:00Z

Highlights

The array-callback-return rule now supports Array.prototype.toSorted.

Features

9b2fcf7 feat: array-callback-return supports Array.prototype.toSorted (#16845) (SUZUKI Sosuke)

Bug Fixes

923f61d fix: false positive with assignment in no-extra-parens (#16872) (Francesco Trotta)

Documentation

f0a9883 docs: split rules documentation (#16797) (Ben Perlmutter)
67aa37b docs: fix typo in command-line-interface (#16871) (Kevin Rouchut)
337f7ed docs: fix width of language input (#16849) (Tanuj Kanti)
71349a1 docs: Configure a Parser page (#16803) (Ben Perlmutter)
de7e925 docs: remove extra line numbers in example (#16848) (jonz94)
ad38d77 docs: Update README (GitHub Actions Bot)

Chores

9dbe06d chore: add type property to array-element-newline schema (#16877) (MHO)
a061527 chore: Remove unused functions (#16868) (Nicholas C. Zakas)

ESLint v8.33.0 released

2023-01-28T00:00:00Z

Highlights

The no-restricted-exports rule gained a new restrictDefaultExports option to control where the default export can be used.
This release continues our ongoing documentation update project. All moved pages should redirect to their new locations, but please let us know if you find any broken links.

Features

2cc7954 feat: add restrictDefaultExports option to no-restricted-exports rule (#16785) (Nitin Kumar)

Documentation

17f4be2 docs: Fix examples in no-multiple-empty-lines rule (#16835) (jonz94)
9c7cfe3 docs: ‘Source Code’ content in ‘Set up Development Environment’ page (#16780) (Ben Perlmutter)
ede5c64 docs: Custom processors page (#16802) (Ben Perlmutter)
2620614 docs: Code of Conduct page (#16781) (Ben Perlmutter)
50a8efd docs: report a sec vulnerability page (#16808) (Ben Perlmutter)
ed60afd docs: Update page titles, section landing pages, and side TOC (#16760) (Ben Perlmutter)
333c712 docs: add background to code-path-diagrams for dark-mode (#16822) (Tanuj Kanti)
f5f7b9b docs: Update README (GitHub Actions Bot)
2aa4f5f docs: no-constant-condition: Add multi-comparison example (#16776) (Sebastian Simon)
40287db docs: Remove Google Group icon (#16779) (Nicholas C. Zakas)
ea10ca5 docs: ‘a .eslint’ -> ‘an .eslint’ for consistency (#16809) (Ben Perlmutter)
3be0748 docs: add example for nodejs lintText api (#16789) (Siva K)
ce4f5ff docs: Replace removed related rules with a valid rule (#16800) (Ville Saalo)

ESLint v8.32.0 released

2023-01-14T00:00:00Z

Highlights

The prefer-regex-literals rule now provides suggestions for some of the problems it reports.
This release reorganizes documentation as part of our ongoing documentation update project. All moved pages should redirect to their new locations, but please let us know if you find any broken links.

Features

fc20f24 feat: add suggestions for redundant wrapping in prefer-regex-literals (#16658) (YeonJuan)

Bug Fixes

b4f8329 fix: ignore directives for no-fallthrough (#16757) (gfyoung)

Documentation

17b65ad docs: IA Update page URL move (#16665) (Ben Perlmutter)
5981296 docs: fix theme switcher button (#16752) (Sam Chen)
6669413 docs: deploy prerelease docs under the /docs/next/ path (#16541) (Nitin Kumar)
78ecfe0 docs: use inline code for rule options name (#16768) (Percy Ma)
fc2ea59 docs: Update README (GitHub Actions Bot)
762a872 docs: Update README (GitHub Actions Bot)

Chores

2952d6e chore: sync templates/*.md files with issue templates (#16758) (gfyoung)
3e34418 chore: Add new issues to triage project (#16740) (Nicholas C. Zakas)

ESLint's 2022 year in review

2023-01-10T00:00:00Z

In February 2022, we shared our plan for 2022, including how the ESLint project as a whole would be spending its sponsorship money for the betterment of the project. In this post, I’ll share what we achieved during the year.

Website redesign

The most recognizable change to the project was undoubtedly the website redesign. The new website was officially launched on June 23 and was immediately met with widespread positive reviews. The designer, Hayden Bleasel, shared his approach for the redesign in a guest post on the newly redesigned website.

We also launched several international language sites, including Chinese, Spanish, German, Japanese, Brazilian Portuguese, French, and Hindi.

The website launch excited a lot of people to the point where we started getting contributions just for the website. As a result, we created a new website team to focus on keeping the new website up-to-date and continuing to make improvements.

This effort cost nearly $60,000 and would not have been possible without the support of our sponsors.

Preview release of the new configuration system

We had been working on the design of a new configuration system for several years, and in 2022, users finally got to see the new system. In August, we released the first preview of the new configuration system through a series of blog posts:

Part 1 explains why we needed a new configuration system and the problems with the current system.
Part 2 explains the new configuration system and the thinking that went into its design.
Part 3 explains how to use the developer preview of the configuration system.

Since we published that third post, the new configuration system is almost complete and is available for use by end users (see the docs for more).

We anticipate the final release of the new configuration system in 2023 along with a transition period where both the new and old configuration systems can be used before the old is eventually removed.

Updates to support ES2022

As we do each year, the ESLint team stays on top of the latest ECMAScript versions to make sure ESLint continues to support the more recent JavaScript syntax and features. This year, we added support for:

You can enable these in your configuration by setting ecmaVersion: 2022 or ecmaVersion: "latest".

Project kickoffs

In addition to our normal maintenance and development, we also kicked off a couple of additional projects:

Documentation Refresh - we hired a technical writer to start reviewing, organizing, and rewriting our documentation. We have never had a documentation-focused project and we felt like 2022 was the right time to start this project given the funds we had available. We anticipate this project to continue until mid-2023.
ESLint Community - the strength of ESLint is in its ecosystem and we had been searching for a way to better organize that ecosystem. As a result, we created the eslint-community GitHub organization as a home for high-value projects in the ESLint ecosystem. We intend this to be a place for projects related to ESLint to live and thrive so that they never fall out of maintenance. We are still working through the details on this and you can expect a follow-up blog post soon.

Income review

During 2022, ESLint received $211,656.13 USD from all of our income sources. You can see the breakdown of our income sources in the following table.

Source	Amount
Open Collective	$142,092.92
GitHub Sponsors	$26,606.61
Tidelift	$29,047.86
Carbon Ads	$13,831.16
Stackaid.us	$77.58
Total	$211,656.13

As usual, most of our donations came through Open Collective followed by GitHub Sponsors. Our Tidelift agreement also provided a good amount of income as did the ad on our website.

We are extremely grateful for the generous donations from companies and individuals that allow the project to continue development.

Top sponsors

The overwhelming majority of our income came from sponsors, and we’re extra grateful to all of the sponsors who donated $1,000 or more during the year.

Sponsor	2022 Donation Total
Chrome Frameworks Fund	$24,500.00
Automattic	$24,000.00
Etsy Open Source	$18,000.00
Salesforce	$13,000.00
Airbnb	$12,000.00
Nx (by Nrwl)	$6,400.00
American Express	$6,000.00
Liftoff	$6,000.00
Contra	$5,000.00
Substack	$5,000.00
Cybozu	$3,152.00
Algolia	$3,000.00
Wix Engineering	$2,400.00
Ignition	$2,400.00
Icons8	$2,400.00
Discord	$2,400.00
Anagram Solver	$2,400.00
launchdarkly	$2,200.00
ThemeIsle	$2,200.00
RIDI	$2,000.00
VPS Server	$2,000.00
Sentry	$1,608.00
HeroCoders	$1,400.00
QuickBooks Tool hub	$1,320.00
Yannick Croissant	$1,200.00

Expenses review

In 2022, we spent $157,270.48 USD on the ESLint project as a whole. This includes regular maintenance and development as well as other costs related to the project. See the table below for an overview.

Category	Amount
Maintenance and Development	-$68,428.23
TSC Stipend (Tidelift)	-$29,047.86
Website Redesign	-$7,167.52
Technical Writing	-$4,147.50
Contributor Pool	-$7,900.00
Payment Processor Fees	-$2,942.67
Health Insurance	-$1,847.86
Open Source Collective Fee	-$12,172.84
Ecosystem/Dependencies	-$14,350.00
Community Management	-$4,000.00
Google Workspace	-$216.00
Tech Writer Hiring & Interviews	-$1,750.00
Community Logo Design	-$3,000.00
Guest Blog Posts	-$300.00
Total	-$157,270.48

Supporting our dependencies and ecosystem

In 2022, the ESLint project donated $14,350.00 USD to ecosystem projects and our dependencies. This is part of our ongoing commitment to supporting projects that are important to ESLint.

Project	Donations
lint-staged	$2,450.00
Ajv	$1,700.00
debug	$1,700.00
eslint-plugin-import	$1,700.00
jsx-eslint	$1,700.00
Sindre Sorhus	$1,700.00
typescript-eslint	$1,700.00
Rollup	$900.00
Eleventy	$800.00
Total	$14,350.00

Looking forward to 2023

While ESLint had a fantastic 2022, we are looking forward to an even better 2023. With the ESLint Community and documentation projects running, we expect to make the ESLint ecosystem even stronger. We are also planning to start on a complete rewrite from the ground up to make sure that ESLint is ready for the next ten years of JavaScript development. This process will likely take place in small, incremental steps as we think through how JavaScript development has changed and will continue to evolve in the future.

We are excited about the future of ESLint and we appreciate your ongoing support.

Updated (2024-02-29): We revised how our financials were reported to correct for errors in our initial calculation and to bring the numbers in this post inline with our 2023 approach to calculating our financials.

ESLint v8.31.0 released

2022-12-31T00:00:00Z

Highlights

The no-underscore-dangle rule gained two new options: allowInArrayDestructuring and allowInObjectDestructuring. Both of these default to true to allow dangling underscores in array and object destructuring for backwards compatibility. Set them to false to check for dangling underscores in destructuring assignments.

Features

52c7c73 feat: check assignment patterns in no-underscore-dangle (#16693) (Milos Djermanovic)
b401cde feat: add options to check destructuring in no-underscore-dangle (#16006) (Morten Kaltoft)
30d0daf feat: group properties with values in parentheses in key-spacing (#16677) (Francesco Trotta)

Bug Fixes

35439f1 fix: correct syntax error in prefer-arrow-callback autofix (#16722) (Francesco Trotta)
87b2470 fix: new instance of FlatESLint should load latest config file version (#16608) (Milos Djermanovic)

Documentation

4339dc4 docs: Update README (GitHub Actions Bot)
4e4049c docs: optimize code block structure (#16669) (Sam Chen)
54a7ade docs: do not escape code blocks of formatters examples (#16719) (Sam Chen)
e5ecfef docs: Add function call example for no-undefined (#16712) (Elliot Huffman)
a3262f0 docs: Add mastodon link (#16638) (Amaresh S M)
a14ccf9 docs: clarify files property (#16709) (Sam Chen)
3b29eb1 docs: fix npm link (#16710) (Abdullah Osama)
a638673 docs: fix search bar focus on Esc (#16700) (Shanmughapriyan S)
f62b722 docs: country flag missing in windows (#16698) (Shanmughapriyan S)
4d27ec6 docs: display zh-hans in the docs language switcher (#16686) (Percy Ma)
8bda20e docs: remove manually maintained anchors (#16685) (Percy Ma)
b68440f docs: User Guide Getting Started expansion (#16596) (Ben Perlmutter)

Chores

65d4e24 chore: Upgrade @eslint/eslintrc@1.4.1 (#16729) (Brandon Mills)
8d93081 chore: fix CI failure (#16721) (Sam Chen)
8f17247 chore: Set up automatic updating of README (#16717) (Nicholas C. Zakas)
4cd87cb ci: bump actions/stale from 6 to 7 (#16713) (dependabot[bot])
fd20c75 chore: sort package.json scripts in alphabetical order (#16705) (Darius Dzien)
10a5c78 chore: update ignore patterns in eslint.config.js (#16678) (Milos Djermanovic)

ESLint v8.30.0 released

2022-12-16T00:00:00Z

Highlights

The no-return-await rule now provides suggestions for some of the problems reported by this rule.

Features

075ef2c feat: add suggestion for no-return-await (#16637) (Daniel Bartholomae)
7190d98 feat: update globals (#16654) (Sébastien Règne)

Bug Fixes

1a327aa fix: Ensure flat config unignores work consistently like eslintrc (#16579) (Nicholas C. Zakas)
9b8bb72 fix: autofix recursive functions in no-var (#16611) (Milos Djermanovic)

Documentation

6a8cd94 docs: Clarify Discord info in issue template config (#16663) (Nicholas C. Zakas)
ad44344 docs: CLI documentation standardization (#16563) (Ben Perlmutter)
293573e docs: fix broken line numbers (#16606) (Sam Chen)
fa2c64b docs: use relative links for internal links (#16631) (Percy Ma)
75276c9 docs: reorder options in no-unused-vars (#16625) (Milos Djermanovic)
7276fe5 docs: Fix anchor in URL (#16628) (Karl Horky)
6bef135 docs: don’t apply layouts to html formatter example (#16591) (Tanuj Kanti)
dfc7ec1 docs: Formatters page updates (#16566) (Ben Perlmutter)
8ba124c docs: update the prefer-const example (#16607) (Pavel)
e6cb05a docs: fix css leaking (#16603) (Sam Chen)

Chores

f2c4737 chore: upgrade @eslint/eslintrc@1.4.0 (#16675) (Milos Djermanovic)
ba74253 chore: standardize npm script names per #14827 (#16315) (Patrick McElhaney)
0d9af4c ci: fix npm v9 problem with file: (#16664) (Milos Djermanovic)
90c9219 refactor: migrate off deprecated function-style rules in all tests (#16618) (Bryan Mishkin)

ESLint v8.29.0 released

2022-12-02T00:00:00Z

Highlights

The no-extra-parens rule has a new option allowParensAfterCommentPattern.
The prefer-named-capture-group rule now provides suggestions for some of the problems reported by this rule.

Features

49a07c5 feat: add allowParensAfterCommentPattern option to no-extra-parens (#16561) (Nitin Kumar)
e6a865d feat: prefer-named-capture-group add suggestions (#16544) (Josh Goldberg)
a91332b feat: In no-invalid-regexp validate flags also for non-literal patterns (#16583) (trosos)

Documentation

0311d81 docs: Configuring Plugins page intro, page tweaks, and rename (#16534) (Ben Perlmutter)
57089b1 docs: add a property assignment example for camelcase rule (#16605) (Milos Djermanovic)
b6ab030 docs: add docs codeowners (#16601) (Strek)
6380c87 docs: fix sitemap and feed (#16592) (Milos Djermanovic)
ade621d docs: perf debounce the search query (#16586) (Shanmughapriyan S)
fbcf3ab docs: fix searchbar clear button (#16585) (Shanmughapriyan S)
f894035 docs: HTTPS link to yeoman.io (#16582) (Christian Oliff)
de12b26 docs: Update configuration file pages (#16509) (Ben Perlmutter)
1ae9f20 docs: update correct code examples for no-extra-parens rule (#16560) (Nitin Kumar)

Chores

7628403 chore: add discord channel link (#16590) (Amaresh S M)
f5808cb chore: fix rule doc headers check (#16564) (Milos Djermanovic)

ESLint v8.28.0 released

2022-11-18T00:00:00Z

Highlights

The no-magic-numbers rule has a new option ignoreClassFieldInitialValues.

Features

63bce44 feat: add ignoreClassFieldInitialValues option to no-magic-numbers (#16539) (Milos Djermanovic)
8385ecd feat: multiline properties in rule key-spacing with option align (#16532) (Francesco Trotta)
a4e89db feat: no-obj-calls support Intl (#16543) (Sosuke Suzuki)

Bug Fixes

c50ae4f fix: Ensure that dot files are found with globs. (#16550) (Nicholas C. Zakas)
9432b67 fix: throw error for first unmatched pattern (#16533) (Milos Djermanovic)
e76c382 fix: allow * 1 when followed by / in no-implicit-coercion (#16522) (Milos Djermanovic)

Documentation

34c05a7 docs: Language Options page intro and tweaks (#16511) (Ben Perlmutter)
3e66387 docs: add intro and edit ignoring files page (#16510) (Ben Perlmutter)
436f712 docs: fix Header UI inconsistency (#16464) (Tanuj Kanti)
f743816 docs: switch to wrench emoji for auto-fixable rules (#16545) (Bryan Mishkin)
bc0547e docs: improve styles for versions and languages page (#16553) (Nitin Kumar)
6070f58 docs: clarify esquery issue workaround (#16556) (Milos Djermanovic)
b48e4f8 docs: Command Line Interface intro and tweaks (#16535) (Ben Perlmutter)
b92b30f docs: Add Rules page intro and content tweaks (#16523) (Ben Perlmutter)
1769b42 docs: Integrations page introduction (#16548) (Ben Perlmutter)
a8d0a57 docs: make table of contents sticky on desktop (#16506) (Sam Chen)
a01315a docs: fix route of japanese translation site (#16542) (Tanuj Kanti)
0515628 docs: use emoji instead of svg for deprecated rule (#16536) (Bryan Mishkin)
68f1288 docs: set default layouts (#16484) (Percy Ma)
776827a docs: init config about specifying shared configs (#16483) (Percy Ma)
5c39425 docs: fix broken link to plugins (#16520) (Ádám T. Nagy)
c97c789 docs: Add missing no-new-native-nonconstructor docs code fence (#16503) (Brandon Mills)

Chores

e94a4a9 chore: Add tests to verify #16038 is fixed (#16538) (Nicholas C. Zakas)
e13f194 chore: stricter validation of meta.docs.description in core rules (#16529) (Milos Djermanovic)
72dbfbc chore: use pkg parameter in getNpmPackageVersion (#16525) (webxmsj)

ESLint v8.27.0 released

2022-11-06T00:00:00Z

Highlights

The new no-new-native-nonconstructor rule protects against newing BigInts and Symbols, which would throw an error. The existing no-new-symbol rule only checks for new Symbol. no-new-native-nonconstructor will take the place of no-new-symbol in eslint:recommended in the next major release.
The new no-empty-static-block rule disallows empty ES2022 class static initialization blocks.

Features

f14587c feat: new no-new-native-nonconstructor rule (#16368) (Sosuke Suzuki)
978799b feat: add new rule no-empty-static-block (#16325) (Sosuke Suzuki)
69216ee feat: no-empty suggest to add comment in empty BlockStatement (#16470) (Nitin Kumar)
319f0a5 feat: use context.languageOptions.ecmaVersion in core rules (#16458) (Milos Djermanovic)

Bug Fixes

c3ce521 fix: Ensure unmatched glob patterns throw an error (#16462) (Nicholas C. Zakas)
886a038 fix: handle files with unspecified path in getRulesMetaForResults (#16437) (Francesco Trotta)

Documentation

ce93b42 docs: Stylelint property-no-unknown (#16497) (Nick Schonning)
d2cecb4 docs: Stylelint declaration-block-no-shorthand-property-overrides (#16498) (Nick Schonning)
0a92805 docs: stylelint color-hex-case (#16496) (Nick Schonning)
74a5af4 docs: fix stylelint error (#16491) (Milos Djermanovic)
324db1a docs: explicit stylelint color related rules (#16465) (Nick Schonning)
94dc4f1 docs: use Stylelint for HTML files (#16468) (Nick Schonning)
cc6128d docs: enable stylelint declaration-block-no-duplicate-properties (#16466) (Nick Schonning)
d03a8bf docs: Add heading to justification explanation (#16430) (Maritaria)
8a15968 docs: add Stylelint configuration and cleanup (#16379) (Nick Schonning)
9b0a469 docs: note commit messages don’t support scope (#16435) (Andy Edwards)
1581405 docs: improve context.getScope() docs (#16417) (Ben Perlmutter)
b797149 docs: update formatters template (#16454) (Milos Djermanovic)
5ac4de9 docs: fix link to formatters on the Core Concepts page (#16455) (Vladislav)
33313ef docs: core-concepts: fix link to semi rule (#16453) (coderaiser)

ESLint v8.26.0 released

2022-10-21T00:00:00Z

Highlights

The no-implicit-globals rule now supports /* exported */ directive comments.
ESLINT_USE_FLAT_CONFIG environment variable can now be used for more control over switching between the current and the new config system.

The @eslint/create-config utility to create ESLint config files has a new option --config:

# npm 6.x
npm init @eslint/config --config semistandard

# npm 7+
npm init @eslint/config -- --config semistandard

Features

4715787 feat: check Object.create() in getter-return (#16420) (Yuki Hirasawa)
28d1902 feat: no-implicit-globals supports exported block comment (#16343) (Sosuke Suzuki)
e940be7 feat: Use ESLINT_USE_FLAT_CONFIG environment variable for flat config (#16356) (Tomer Aberbach)
dd0c58f feat: Swap out Globby for custom globbing solution. (#16369) (Nicholas C. Zakas)

Bug Fixes

df77409 fix: use baseConfig constructor option in FlatESLint (#16432) (Milos Djermanovic)
33668ee fix: Ensure that glob patterns are matched correctly. (#16449) (Nicholas C. Zakas)
740b208 fix: ignore messages without a ruleId in getRulesMetaForResults (#16409) (Francesco Trotta)
8f9759e fix: --ignore-pattern in flat config mode should be relative to cwd (#16425) (Milos Djermanovic)
325ad37 fix: make getRulesMetaForResults return a plain object in trivial case (#16438) (Francesco Trotta)
a2810bc fix: Ensure that directories can be unignored. (#16436) (Nicholas C. Zakas)
35916ad fix: Ensure unignore and reignore work correctly in flat config. (#16422) (Nicholas C. Zakas)

Documentation

651649b docs: Core concepts page (#16399) (Ben Perlmutter)
631cf72 docs: note --ignore-path not supported with flat config (#16434) (Andy Edwards)
1692840 docs: fix syntax in examples for new config files (#16427) (Milos Djermanovic)
d336cfc docs: Document extending plugin with new config (#16394) (Ben Perlmutter)

Chores

e917a9a ci: add node v19 (#16443) (Koichi ITO)
4b70b91 chore: Add VS Code issues link (#16423) (Nicholas C. Zakas)
232d291 chore: suppress a Node.js deprecation warning (#16398) (Koichi ITO)

ESLint use at Cesium through years of a changing ecosystem

2022-10-18T00:00:00Z

Background

CesiumJS is an open source JavaScript library for 3D geospatial visualization. Cesium’s roots are in aerospace with our first use case being accurate visualization of satellites and spacecraft. Now with more than 4,000,000 downloads and 9000 stars on GitHub, CesiumJS has a large community of users and contributors. Users from all over the world have used CesiumJS for a variety of different applications, from mapping and data analysis to building interactive simulations for satellites, event planning, open source intelligence and even for building flight simulators.

Switching to ESLint

As an open source project with frequent external contributions, it is important that we have clear and consistent coding conventions along with automated ways of enforcing them. Development started in 2011, and the first version of Cesium was released in 2014. As new browser APIs and standards have emerged, ensuring that CesiumJS stays compatible with modern use cases has been very important to us.

Initially, CesiumJS used JSHint for static analysis, because it was the standard at the time. In 2017, we switched over to ESLint because it was better at keeping pace with the rapid nature of ECMAScript standards development. ESLint enabled enforcement of style rules through linting and applying automatic fixes for a lot of those rules. Perhaps most important of all was the ability to create extensible configurations that fit our own coding standards and extend configurations made by others in the community. In this post, I will explain how we, the maintainers of CesiumJS, use ESLint for ensuring code quality, enforcing consistency, and reducing developer burden in adhering to our code style and standards across our open source and private projects.

How we use ESLint

The earlier in the development process a developer is able to catch an issue, the less expensive it is to fix it. This “shifting left” strategy is a key priority for us and that is why we incorporate linting into the developer workflow so that developers are informed of potential issues in their code as they write it or before they commit it.

First, Visual Studio Code is the IDE of choice at Cesium, so we include the official ESLint VS Code extension in .vscode/extensions.json so that users are prompted to install the extension when they clone the repository and open it in VS Code.

Second, we use the husky package to install pre-commit hooks to ensure that the lint command is run every time code is committed to the repository.

Last, we also run the lint script as part of our CI step.

These tools are replicated for all our repositories to ensure a consistent and efficient experience in development and in review. Maintaining consistency in the code and the tools reduces the burden on developers working on different projects and makes it easier to onramp developers on new projects.

At Cesium, we maintain two open source shareable ESLint configurations: one for Node.js projects and another for browser environments. Often, both configurations are used in the same repository as there is often server/script code to accompany the client/web code. Our configurations rely heavily on the default ESLint recommended ruleset. Because we use Prettier for code formatting in all our projects, we also add the Prettier ruleset to ensure that there are no conflicts between the linter and the formatter. Projects often also end up extending the base source configuration to create a testing configuration for the Jasmine environment.

Prior to 2022, CesiumJS had been locked to ECMAScript 2009, primarily due to browser constraints imposed by supporting Internet Explorer. We used eslint-plugin-es to restrict or allow specific language features. Once we dropped support for Internet Explorer, we were free to upgrade to a more modern version of ECMAScript. We set our version to ECMAScript 2020, and through ESLint the process was mostly automated thanks to the fix command. There were a lot of benefits that were instantly apparent to us; to name a couple of examples, GLSL shader strings were much easier to read because of the string template syntax and let and const made the code a lot more readable through clearer scoping and enforcing immutable references where needed.

Our current ESLint configuration allows users to use all modern features available up to ES2020. But since CesiumJS is a 3D engine, it’s important that developers balance the convenience of ES6+ code syntax with its performance impact. In areas of the code that are run enough times to make a significant impact, such as per-frame rendering loop code, a simple for loop may be better than an Array.forEach(). We don’t impose blanket rules on situations like this since the nuance is difficult to automate. Instead we document the best practices in our coding guide and have developers and reviewers measure the impact of such choices on a case-by-case basis.

Conclusion

ESLint is an extremely important part of our development process. It’s a tool that helps us maintain a very large code base that is well-tested, stable, performant and has a strong coding style. It also helps us attract contributors and enables us to be confident in the code we ourselves write and review. If you’re interested in learning more about Cesium, head over to our blog for more information.

ESLint v8.25.0 released

2022-10-07T00:00:00Z

Highlights

Formatters now have access to the --max-warnings threshold when it is exceeded. See Working with Custom Formatters - The context Argument for details.
The new config system no longer supports .eslintignore files, --ignore-path CLI option and ignorePath API option, due to observed incompatibilities with ignores in eslint.config.js configuration files. For ignoring files in the new config system, please see Globally ignoring files with ignores. We are still working on several other issues related to this feature.

Features

173e820 feat: Pass --max-warnings value to formatters (#16348) (Brandon Mills)
6964cb1 feat: remove support for ignore files in FlatESLint (#16355) (Milos Djermanovic)
1cc4b3a feat: id-length counts graphemes instead of code units (#16321) (Sosuke Suzuki)

Documentation

90c6028 docs: Conflicting fixes (#16366) (Ben Perlmutter)
5a3fe70 docs: Add VS to integrations page (#16381) (Maria José Solano)
49bd1e5 docs: remove unused link definitions (#16376) (Nick Schonning)
3bd380d docs: typo cleanups for docs (#16374) (Nick Schonning)
b3a0837 docs: remove duplicate words (#16378) (Nick Schonning)
a682562 docs: add BigInt to new-cap docs (#16362) (Sosuke Suzuki)
f6d57fb docs: Update docs README (#16352) (Ben Perlmutter)
7214347 docs: fix logical-assignment-operators option typo (#16346) (Jonathan Wilsson)

Chores

1f78594 chore: upgrade @eslint/eslintrc@1.3.3 (#16397) (Milos Djermanovic)
8476a9b chore: Remove CODEOWNERS (#16375) (Nick Schonning)
720ff75 chore: use “ci” for Dependabot commit message (#16377) (Nick Schonning)
42f5479 chore: bump actions/stale from 5 to 6 (#16350) (dependabot[bot])
e5e9e27 chore: remove jsdoc dev dependency (#16344) (Milos Djermanovic)

ESLint v8.24.0 released

2022-09-23T00:00:00Z

Highlights

One new rule has been added: logical-assignment-operators

Features

1729f9e feat: account for sourceType: "commonjs" in the strict rule (#16308) (Milos Djermanovic)
b0d72c9 feat: add rule logical-assignment-operators (#16102) (fnx)
f02bcd9 feat: array-callback-return support findLast and findLastIndex (#16314) (Sosuke Suzuki)

Documentation

2c152ff docs: note false positive Object.getOwnPropertyNames in prefer-reflect (#16317) (AnnAngela)
bf7bd88 docs: fix warn severity description for new config files (#16324) (Nitin Kumar)
8cc0bbe docs: use more clean link syntax (#16309) (Percy Ma)
6ba269e docs: fix typo (#16288) (jjangga0214)

Chores

131e646 chore: Upgrade @humanwhocodes/config-array for perf (#16339) (Nicholas C. Zakas)
504fe59 perf: switch from object spread to Object.assign when merging globals (#16311) (Milos Djermanovic)

ESLint v8.23.1 released

2022-09-12T00:00:00Z

Highlights

This release includes a significant performance improvement in the indent rule as well as some bug fixes for the new eslint.config.js config system.

Bug Fixes

b719893 fix: Upgrade eslintrc to stop redefining plugins (#16297) (Brandon Mills)
734b54e fix: improve autofix for the prefer-const rule (#16292) (Nitin Kumar)
6a923ff fix: Ensure that glob patterns are normalized (#16287) (Nicholas C. Zakas)
c6900f8 fix: Ensure globbing doesn’t include subdirectories (#16272) (Nicholas C. Zakas)

Documentation

16cba3f docs: fix mobile double tap issue (#16293) (Sam Chen)
e098b5f docs: keyboard control to search results (#16222) (Shanmughapriyan S)
1b5b2a7 docs: add Consolas font and prioritize resource loading (#16225) (Amaresh S M)
1ae8236 docs: copy & use main package version in docs on release (#16252) (Jugal Thakkar)
279f0af docs: Improve id-denylist documentation (#16223) (Mert Ciflikli)

Chores

38e8171 perf: migrate rbTree to js-sdsl (#16267) (Zilong Yao)
1c388fb chore: switch nyc to c8 (#16263) (唯然)
67db10c chore: enable linting .eleventy.js again (#16274) (Milos Djermanovic)
42bfbd7 chore: fix npm run perf crashes (#16258) (唯然)

ESLint v8.23.0 released

2022-08-26T00:00:00Z

Highlights

The new config system is now incorporated into the CLI, along with the existing config system. To opt-in to the new config system, place a eslint.config.js file in the root of your project. Please note that this is still an experimental feature and we welcome your feedback!
The no-fallthrough rule has a new option allowEmptyCase.
The no-warning-comments rule has a new option decoration.

Features

3e5839e feat: Enable eslint.config.js lookup from CLI (#16235) (Nicholas C. Zakas)
30b1a2d feat: add allowEmptyCase option to no-fallthrough rule (#15887) (Amaresh S M)
43f03aa feat: no-warning-comments support comments with decoration (#16120) (Lachlan Hunt)

Documentation

b1918da docs: package.json conventions (#16206) (Patrick McElhaney)
0e03c33 docs: remove word immediately (#16217) (Strek)
c6790db docs: add anchor link for “migrating from jscs” (#16207) (Percy Ma)
7137344 docs: auto-generation edit link (#16213) (Percy Ma)

Chores

2e004ab chore: upgrade @eslint/eslintrc@1.3.1 (#16249) (Milos Djermanovic)
d35fbbe chore: Upgrade to espree@9.4.0 (#16243) (Milos Djermanovic)
ed26229 test: add no-extra-parens tests with rest properties (#16236) (Milos Djermanovic)
deaf69f chore: fix off-by-one min-width: 1023px media queries (#15974) (Milos Djermanovic)
63dec9f refactor: simplify parseListConfig (#16241) (Milos Djermanovic)

ESLint v8.22.0 released

2022-08-13T00:00:00Z

Highlights

The new config system preview now supports caching. To learn more, check out the three-part series on our blog! (1, 2, 3)

Features

2b97607 feat: Implement caching for FlatESLint (#16190) (Nicholas C. Zakas)
fd5d3d3 feat: add methodsIgnorePattern option to object-shorthand rule (#16185) (Milos Djermanovic)

Documentation

9f5a752 docs: optimize image assets (#16170) (Sam Chen)
61b2948 docs: add svgo command to pre commit hook (#16178) (Amaresh S M)
784096d docs: improve search result UI (#16187) (Sam Chen)
d0f4cb4 docs: use shorthand property name in example (#16180) (Kevin Elliott)

Chores

10a6e0e chore: remove deploy workflow for playground (#16186) (Milos Djermanovic)

Redesigning ESLint

2022-08-10T00:00:00Z

Hi! My name’s Hayden. I’m a designer and developer and, until recently, I ran a little agency called Jellypepper.

We were fortunate enough to work with the ESLint team on their new brand and website. I’m a huge fan of ESLint and use it every day, even going to the effort of writing my own 600-line ESLint config to use across all my React, Next.js and Expo projects.

Nicholas originally reached out to us on Twitter to kick off the largest project the ESLint team has taken on in its nine years of existence. He wanted to create a stronger brand identity for the ESLint team and its community, and make the website more functional, easier to navigate, and more useful to everyone from new users to established users.

Hi Hayden, I wanted to say thanks for the donation to ESLint. As it so happens, the project is looking for a bit of a rebrand (keep the logo, change everything else) and website redesign, so I was wondering if you’d be interested. It just seemed like a potentially good match.

This was a bit of a dream project for me 😅 So, needless to say, we were totally in.

The Brand

The ESLint Brand is an interesting one - without too much official visual design, the team has managed to create a brand that is unique and widely recognized by the developer community.

The Logo

The logomark is at the core of ESLint’s brand identity and one of the most identifiable pieces. It’s a connection to their ecosystem - you can find it everywhere, from IDE marketplaces to corporate sponsorship pages across the web. It carries with it the expectation of a community of developers who are passionate about the code they write.

While we kept the icon (given its widespread usage in websites, IDEs, platforms and projects), we wanted to make it that little bit more refined, modern and flexible. By bringing it together our new primary typeface, Space Grotesk (more on this below), we created a new ESLint logomark. Due to its simplicity, it works in a variety of colours and spaces.

The Typeface

As a content-driven organization, typography is at the heart of the new ESLint brand. The website, docs, and blog all require typography to be readable and enjoyable. The brand leverages a purposeful set of typographic styles designed to make the content as accessible as possible for everyone.

From a technical point of view, we wanted fonts that were widely accessible and conveniently located, so could access it everywhere (particularly on other Google products such as Docs and Slides) and it fits with the free and open-source theme.

We decided to go with Space Grotesk — a fantastic, characteristic font that balances that flair with the technical geometric elements reflecting a more developer-centric side. It creates character with its idiosyncratic details that share principles with the logomark and brings life and energy to the brand by showcasing its more technical details.

Space Grotesk works hand-in-hand with its origin sister font, Space Mono. It was developed for editorial use in headline and display typography; the letterforms infuse a geometric foundation and grotesque details with qualities often found in headline typefaces of the 1960s, many of which have since been co-opted by science fiction films, television, and literature.

The Colors

ESLint’s color palette speaks to the brand in ways that are every bit as powerful as the copy and logo. It not only affects how the brand design looks, but can go as far as to elicit emotion and reflect the personality of the ESLint brand. Colors are the first impression a design makes, and as such, play an important role in a design’s look and feel.

While color can be subjective, it’s clear that good colors can attract and convert users. Bad colors, on the other hand, can turn away users and even make designs inaccessible and unusable.

Due to the functional nature of ESLint, we chose to keep it simple with a primary, neutral and small set of secondary palettes. The new primary color palette is derived from the original logo — we use the two existing colors to create a unique primary tonal range.

The Website

Next up was the redesign of the ESLint website. Besides maximising the visual appeal of the site, we had a few goals we wanted to achieve for each page. For example, on the homepage:

We wanted to include the latest and upcoming versions of ESLint in the hero section. This was a key part of the design, as it would be the first time we had a dedicated section for ESLint updates.
We wanted to promote sponsorship. ESLint relies on donations for ongoing maintenance and development, and we wanted to make sure that we could help accelerate the growth of the project.
We wanted to show ESLint in action — how it can be used in the real world, and how it can be used to make your code more readable.
We wanted to showcase some of the incredible stats that ESLint has amassed — as of right now, that’s 9M dependents, 25.7M weekly downloads and 21K stars on GitHub.

I also wanted to introduce some animation and life into the ESLint homepage hero while giving our audience a sense of what it’s like to work with ESLint.

The red underline in VS Code is synonymous with ESLint, as it is the way VS Code implements ESLint action items. Using these visual indicators, I created a small but fun interaction that gives our visitors a simplified experience.

I was particularly happy with how this idea turned out! 💡

By incorporating elements of the wider brand including IDE integration, code snippets and supporter logos, we brought the brand to life. Plus, no dev site would be complete without a testimonial from Addy Osmani.

The Docs

Next up was the mack daddy, redesigning the ESLint documentation. The docs are a central part of ESLint’s ecosystem and are the place where users find information about the project as well as the codebase.

We wanted to give it a bit of a revamp, creating a consistent information architecture (IA) across all pages, as well as making the pages easier to scan and navigate. We also added a version dropdown to view previous versions of the docs.

I also published the little Carbon Ads component as a Figma Community file!

The Playground

The last part of the project was a new microsite called Playground! It’s a fantastic little tool that allows you to create an ESLint configuration file with easy-to-use settings and test your code against it. Then, once you’re happy with it, you can download your config file to use locally. Its also a fantastic way of allowing new users to try ESLint directly in the browser.

We started designing Playground with a few key requirements in mind — specifically we wanted to make it easy to use, and to make it easy to create and share reproducible bugs with ESLint. Users should also be able to switch between different versions of ESLint, see potential fixes to given problems and install plugins. Ultimately the team couldn’t implement all of these features, but we designed for them all the same.

There were a few tricky design challenges to overcome here — particularly around the density of information. Exposing all rules in the UI would make things visually difficult to parse, so we needed a way of adding rules to the UI without having to scroll down to the bottom of the page, then customising the value of each rule easily.

What’s next?

The ESLint team are currently rolling out everything above (you’re on the new website right now!).

I want to thank the ESLint team, especially Nicholas, for the opportunity to work on this project. I was also very fortunate to work with such talented and passionate people, such as Sara and Gavin.

If you have any questions, comments, or feedback on the ESLint brand, please reach out to me on Twitter at @haydenbleasel.

Happy linting, folks! ✌️

ESLint's new config system, Part 3: Developer preview

2022-08-08T00:00:00Z

In my previous post, I explained the fundamental concepts of using the new “flat” config system. The new config system isn’t yet tied into the CLI while we do more internal testing, but we did want to give the ESLint community a chance to experiment with flat config while we work on incorporating it into the CLI. So ESLint v8.21.0 incorporates several ways to try out flat config as we work on it. Please keep in mind that everything mentioned in this post is experimental and we would love your feedback as you try it out.

Using flat config with the `Linter` class

If you are currently using Linter from the eslint package, you can enable flat config by setting configType: "flat" as an option on the constructor. Here’s an example:

const linter = new Linter({ configType: "flat" });

const messages = linter.verify("new Map()", {
    languageOptions: {
        ecmaVersion: 5,
        sourceType: "script"
    },
    rules: {
        "no-undef": "error"
    }
}, "filename.js");

When you pass configType: "flat" as an option, Linter expects that any configuration objects that are passed to verify() will be in flat config format. In this example, the second argument to verify() is a flat config object (you can pass either a single object or an array of objects). Any call to verify() will assume that the text being linted is a JavaScript file whose filename ends with .js, but it’s always a good idea to pass in an explicit filename as the third argument.

While this base case works the same regardless of which config system you’re using, there are some important differences:

defineRule(), defineRules(), and defineParser() now throw errors. Runtime plugins (discussed in my previous post) make these methods obsolete.
getRules() also throws an error. This method would return different data depending on when it was called, so it can’t be used with flat config.

Using flat config with the `ESLint` class

While implementing flat config we discovered that it would be too difficult to create an option to switch between config systems like we did for Linter. Instead, we created a FlatESLint class that encapsulates all of the existing functionality in ESLint but uses flat config instead of eslintrc. The FlatESLint class is intended only as a preview of functionality; once we switch over to flat config permanently, the current ESLint class will be deleted and FlatESLint will be renamed to ESLint.

For now, you can access FlatESLint through the use-at-your-own-risk entrypoint, like this:

// ESM
import pkg from "eslint/use-at-your-own-risk";
const { FlatESLint } = pkg;

// CommonJS
const { FlatESLint } = require("eslint/use-at-your-own-risk");

After that, you can use FlatESLint in the same way as ESLint, such as:

const eslint = new FlatESLint({
    cwd: originalDir,
    overrideConfigFile: "other.config.js"
});
const results = await eslint.lintText("foo");

As with Linter, there are a few differences between FlatESLint and ESLint worth pointing out:

Caching is not yet implemented in FlatESLint, so cache: true throws an error.
The useEslintrc option has been removed. If you want to avoid automatic loading of eslint.config.js without specifying an alternate config file, set overrideConfigFile: true.
The envs option has been removed.
The resolvePluginsRelativeTo option has been removed.
The rulePaths option has been removed. Custom rules must be added directly by config.

Testing rules with flat config and the `RuleTester` class

Similar to the ESLint class, there was no easy way to provide an option to switch between eslintrc and flat config, so we created a separate FlatRuleTester class. Also similar to ESLint, the FlatRuleTester class is temporary and will eventually be renamed RuleTester once we have switched completely over to flat config. You can access FlatRuleTester like this:

// ESM
import pkg from "eslint/use-at-your-own-risk";
const { FlatRuleTester } = pkg;

// CommonJS
const { FlatRuleTester } = require("eslint/use-at-your-own-risk");

Any place where you could specify an eslintrc config in RuleTester needs to be a flat config in FlatRuleTester. Here are some examples:

const ruleTester = new FlatRuleTester({
    languageOptions: {
        ecmaVersion: 5,
        sourceType: "script"
    }
});

ruleTester.setDefaultConfig({
    languageOptions: {
        ecmaVersion: 5,
        sourceType: "script"
    }
});

In individual tests, you can use languageOptions directly in each test:

ruleTester.run("my-rule", rule, {
    valid: [
        {
            code: "var test = 'foo'",
            languageOptions: {
                sourceType: "script"
            }
        },
        {
            code: "var test2 = 'bar'",
            languageOptions: {
                globals: { test: true }
            }
        }
    ],
    invalid: [
        {
            code: "bar",
            languageOptions: {
                sourceType: "script"
            },
            errors: 1
        }
    ]
});

Some things to keep in mind when using FlatRuleTester:

The default ecmaVersion is now "latest", so if you aren’t specifying ecmaVersion in your tests, there may be an incompatibility because eslintrc’s default ecmaVersion was 5.
The default sourceType is now "module", so if you aren’t specifying sourceType in your tests, there may be an incompatibility because eslintrc’s default sourceType was "script". This shows up mostly when dealing with variables in the global scope.

Conclusion

We think that the new config system will be a great experience for ESLint users, but in order for that to happen, we have to make sure that the ESLint ecosystem is ready for these changes. That’s why we’ve put together this developer preview to let all of our plugin, custom rule, parser, and shareable config authors get an early look at how their packages will work in the new config system. This is your opportunity to give us your feedback and help work through any incompatibilities or problems with flat config.

Please try out flat config with your packages and let us know how it goes by starting a discussion or stopping by the Discord #developers channel if you have questions or opening an issue if you discover a problem.

We appreciate your help and feedback!

ESLint's new config system, Part 2: Introduction to flat config

2022-08-05T00:00:00Z

In my previous post, I talked about how the eslintrc config system had grown to be more complex than necessary through a series of small, incremental changes. The flat config system, on the other hand, was designed from the start to be simpler in a number of ways. We took all of the learnings from the previous six years of ESLint development to come up with a holistic approach to configuration that took the best of eslintrc and combined it with the way other JavaScript-related tools handled configuration. The result is something that hopefully feels familiar to existing ESLint users and is far more powerful than what was possible before.

Docs: Read more about flat config system in the official documentation.

The goals of flat config

To set the stage for the changes in flat config, we had several goals:

Logical defaults - the way people write JavaScript has changed a lot in the past nine years, and we wanted the new config system to reflect our current reality rather than the one we lived in when ESLint was first released.
One way to define configs - we didn’t want folks to have multiple ways to do the same thing any longer. There should be one way to define configs for any given project.
Rules configs should remain unchanged - we felt like the way rules were configured already worked fine, so to make it easier to transition to flat config, we didn’t want to make any changes to rule configs. The same rules key can be used the same way in flat config.
Use native loading for everything - one of our biggest regrets about eslintrc was recreating the Node.js require resolution in a custom way. This was a significant source of complexity and, in hindsight, unnecessary. Going forward, we wanted to leverage the loading capabilities of the JavaScript runtime directly.
Better organized top-level keys - the number of keys at the top-level of eslintrc had grown dramatically since ESLint was released. We need to look at which keys were necessary and how they related to one another.
Existing plugins should work - the ESLint ecosystem is filled with hundreds of plugins. It was important that these plugins continued to work.
Backwards compatibility should be a priority - even though we are moving to a new config system, we didn’t want to leave all of the existing ecosystem behind. In particular, we wanted to have ways for shareable configs to continue to work as closely as possible. While we knew 100% compatibility was probably unrealistic, we wanted to do our best to ensure existing shareable configs would work.

With these goals in mind, we came up with the new flat config system.

Setting logical defaults for linting

When ESLint was first created, ECMAScript 5 was the most recent version of JavaScript and most files were written as “shared everything” scripts or CommonJS modules (for Node.js). ECMAScript 6 was on the horizon but no one knew how quickly it would be implemented or how modules (ESM) would end up being used. So ESLint’s defaults were to assume all files were ECMAScript 5. We ended up with the ecmaVersion parser configuration to allow people to opt-in to ECMAScript 6 when they were ready.

Fast forward to 2022: ECMAScript is constantly evolving and ESM is the standard module format everyone is using. We couldn’t really change the default settings of eslintrc without potentially breaking a lot of existing configurations, but we could definitely make a change with flat config.

Flat config features the following defaults:

ecmaVersion: "latest" for all JavaScript files - That’s right, by default all JavaScript files will be set to the latest version of ECMAScript. This mimics how JavaScript runtimes work, in that every upgrade means you are opting-in to the latest and greatest version of JavaScript. This change should mean that you probably won’t have to manually set ecmaVersion in your config unless you want to enforce a previous version due to runtime constraints. You will still be able to set ecmaVersion all the way down to 3 if necessary.
sourceType: "module" for all .js and .mjs files - By default, flat config assumes you are writing ESM. If not, you can always set sourceType back to "script".
sourceType: "commonjs" for .cjs files - We are still in a transition period where a lot of Node.js code is written in CommonJS. To support those users, we added a new sourceType of "commonjs" that configures everything correctly for that environment.
ESLint searches for .js, .mjs, and .cjs files - With eslintrc, ESLint only ever searched for .js files when you passed a directory name on the command line, and you would need to use the --ext flag to define more. With flat config, all three of the most common JavaScript filename extensions are automatically searched.

We are pretty excited about these new defaults as we think this will help people onboard to ESLint faster and with less confusion.

The new config file: `eslint.config.js`

In contrast to eslintrc, which allowed multiple config files in multiple locations, multiple config file formats, and even package.json-based configs, flat config has just one location for all of your project’s configuration: the eslint.config.js file. By limiting configuration to one location and one format, we can take advantage of the JavaScript runtime’s loading mechanism directly and avoid the need for custom parsing of config files.

When the ESLint CLI is used, it searches for eslint.config.js from the current working directory and if not found will continue the search up the directory’s ancestors until the file is found or the root directory is hit. That one eslint.config.js file contains all of the configuration information for that run of ESLint so it dramatically reduces the disk access required as compared to eslintrc, which had to check each directory from the linted file location up to the root for any additional config files.

Additionally, using a JavaScript file allowed us to rely on users to load additional information that their config file might need. Instead of extends and plugins loading things by name, you can now just use import and require as necessary to bring in those additional resources. Here’s an example of what an eslint.config.js file looks like:

export default [
    {
        files: ["**/*.js"],
        rules: {
            "semi": "error",
            "no-unused-vars": "error"
        }
    }
];

An eslint.config.js file exports an array of config objects. Read on to understand more about this example.

Glob-based configs everywhere

While the overrides key in eslintrc was the source of a lot of complexity, one thing was very clear: people really liked being able to define configuration by glob patterns in their config file. Because we wanted to eliminate the config cascade of eslintrc, we had to use glob patterns to enable the same type of config overrides. We used the overrides configs as the basis for flat config.

Each config object can have optional files and ignores keys specifying minimatch-based glob patterns to match files. A config object only applies to a file if the filename matches a pattern in files (or if there is no files key, in which case it will match all files). The ignores key filters out files from the list of files, so you limit which files the config object applies to. For instance, maybe your test files live in the same directory as your source file and you want a config object to apply only to the source files. You could do so like this:

export default [
    {
        files: ["**/*.js"],
        ignores: ["**/*.test.js"],
        rules: {
            "semi": "error",
            "no-unused-vars": "error"
        }
    }
];

Here, the config object will match all JavaScript files and then filter out any files ending with .test.js.

What if you want to ignore files completely? You can do that by specifying a config object that has only an ignores key, like this:

export default [
    {
        ignores: ["**/*.test.js"]
    },
    {
        files: ["**/*.js"],
        rules: {
            "semi": "error",
            "no-unused-vars": "error"
        }
    }
];

With this config, all JavaScript files ending with .test.js will be ignored. You can think of this as the equivalent of ignorePatterns in eslintrc, albeit with minimatch patterns.

Goodbye `extends`, hello flat cascade

While we wanted to get rid of the directory-based config cascade, flat config actually still has a flat cascade defined directly in your eslint.config.js file. Inside of the array, ESLint finds all config objects that match the file being linted and merges them together in much the same way that eslintrc did. The only real difference is the merge happens from the top of the array down to the bottom instead of using files in a directory structure. For example:

export default [
    {
        files: ["**/*.js", "**/*.cjs"],
        rules: {
            "semi": "error",
            "no-unused-vars": "error"
        }
    },
    {
        files: ["**/*.js"],
        rules: {
            "no-undef": "error",
            "semi": "warn"
        }
    }
];

This config has two config objects with overlapping files patterns. The first config object applies to all .js and .cjs files while the second applies only to .js files. When linting a file ending with .js, ESLint combines both config objects to create the final config for the file. Because the second config sets semi to a severity of "warn", that takes precedence over the "error" that was set in the first config. The last matching config always wins when there is a conflict.

What this means for shareable configs is that you can insert them directly into the array instead of using extends, such as:

import customConfig from "eslint-config-custom";

export default [
    customConfig,
    {
        files: ["**/*.js", "**/*.cjs"],
        rules: {
            "semi": "error",
            "no-unused-vars": "error"
        }
    },
    {
        files: ["**/*.js"],
        rules: {
            "no-undef": "error",
            "semi": "warn"
        }
    }
];

Here, customConfig is inserted first in the array so that it becomes the base of configuration for this file. Each of the following config objects builds upon that base to create the final config for a given JavaScript file.

Reimagined language options

ESLint has always had a strange mix of options that affected how JavaScript was interpreted. There was the top-level globals key that modified available global variables, and ecmaVersion and sourceType as parserOptions, not to mention env to add more globals. Perhaps the most confusing is that you had to set both ecmaVersion and add an environment like es6 to enable both the syntax you wanted and ensure that the correct global variables would be available.

In flat config, we moved all keys related to JavaScript evaluation into a new top-level key called languageOptions.

Setting `ecmaVersion` in flat config

The biggest change is that we moved ecmaVersion out of parserOptions and directly into languageOptions. This better reflects this key’s new behavior, which is to enable both syntax and global variables based on the specified version of ECMAScript. For example:

export default [
    {
        files: ["**/*.js"],
        languageOptions: {
            ecmaVersion: 6
        }
    }
];

This config has downgraded ecmaVersion to 6. Doing so ensures that all of the ES6 syntax and all of the ES6 globals are available. (Any custom parsers used will still receive this value of ecmaVersion.)

Setting `sourceType` in flat config

Next, we moved sourceType into languageOptions. Similar to ecmaVersion, this key affects not just how a file is parsed, but also how ESLint evaluates its scope structure. We kept the traditional "module" for ESM and "script" for scripts, and also added "commonjs", which lets ESLint know that it should treat the file as CommonJS (which also enables CommonJS-specific globals). If you are using ecmaVersion: 3 or ecmaVersion: 5, be sure to set sourceType: script, like this:

export default [
    {
        files: ["**/*.js"],
        languageOptions: {
            ecmaVersion: 5,
            sourceType: "script"
        }
    }
];

Goodbye environments, hello `globals`

Environments in eslintrc provided a known set of globals and were a constant source of confusion for users. They need to be kept up to date (especially in the case of browser) and that update needs to wait for ESLint releases. Plus, we had hooked some additional functionality onto environments to make it easier to work with Node.js, and in the end, we made a mess.

For flat config, we decided to remove the env key completely. Why? Because it’s no longer needed. All of the custom functionality we hooked onto environments for use with Node.js is now covered by sourceType: "commonjs", so all that was left was for environments to manage global variables. It doesn’t make sense for ESLint to do this in the core, so we are handing this responsibility back to you.

Years ago, we worked with Sindre Sorhus to create the globals package, which extracted all of the environment information from ESLint so that it would be available to other packages. ESLint then used globals as the source for its environments.

With flat config, you can use the globals package directly, updating it whenever you want, to get all of the same functionality that environments used to provide. For example, here is how you add browser globals into your configuration:

import globals from "globals";

export default [
    {
        files: ["**/*.js"],
        languageOptions: {
            globals: {
                ...globals.browser,
                myCustomGlobal: "readonly"
            }
        }
    }
];

The languageOptions.globals key works the same as it did in eslintrc, only now, you can use JavaScript to dynamically insert any global variables that you want.

Custom parsers and parser options are mostly the same

The parser and parserOptions keys have now moved into the languageOptions key, but they mostly work the same as in eslintrc with two specific differences:

You can now insert the parser object directly into the config.
Parsers can now be bundled with plugins and you can specify a string value for parser to use a parser from a plugin. (Described more in the next section.)

Here’s an example using the Babel ESLint parser:

import babelParser from "@babel/eslint-parser";

export default [
    {
        files: ["**/*.js", "**/*.mjs"],
        languageOptions: {
            parser: babelParser
        }
    }
];

This configuration ensures that the Babel parser, rather than the default, will be used to parse all files ending with .js and .mjs.

You can also pass options directly to the custom parser by using the parserOptions key in the same way as it works in eslintrc:

import babelParser from "@babel/eslint-parser";

export default [
    {
        files: ["**/*.js", "**/*.mjs"],
        languageOptions: {
            parser: babelParser,
            parserOptions: {
                requireConfigFile: false,
                babelOptions: {
                    babelrc: false,
                    configFile: false,
                    // your babel options
                    presets: ["@babel/preset-env"],
                }
            }
        }
    }
];

More powerful and configurable plugins

The strength of ESLint is the ecosystem of plugins that individuals and companies maintain to customize their linting strategy. As such, we wanted to be sure that existing plugins continued to work without modification as well as allowing plugins to do things they were never able to do in the past.

On the surface, using a plugin in flat config looks very similar to using a plugin in eslintrc. The big difference is that eslintrc used strings whereas flat configs uses objects. Instead of specifying the name of a plugin, you import the plugin directly and place it into the plugins key, as in this example:

import jsdoc from "eslint-plugin-jsdoc";

export default [
    {
        files: ["**/*.js"],
        plugins: {
            jsdoc
        },
        rules: {
            "jsdoc/require-description": "error",
            "jsdoc/check-values": "error"
        }
    }
];

This config uses the eslint-plugin-jsdoc plugin by importing it as a local jsdoc variable and then inserting it into the plugins key in the config. After that, the rules inside the plugin are referenced using the jsdoc namespace.

Note: Because plugins are now imported like any other JavaScript module, there’s no more strict enforcement of plugin package names. You no longer need to include eslint-plugin- as the prefix for your package names…but we would like it if you did.

Personalized plugin namespaces

Because the name of the plugin in your config is now decoupled from the name of the plugin package, you can choose any name you want, as in this example:

import jsdoc from "eslint-plugin-jsdoc";

export default [
    {
        files: ["**/*.js"],
        plugins: {
            jsd: jsdoc
        },
        rules: {
            "jsd/require-description": "error",
            "jsd/check-values": "error"
        }
    }
];

Here, the plugin is named jsd in the config, so the rules also use jsd to indicate which plugin they are coming from.

From `--rulesdir` to runtime plugins

With eslintrc, rules needed to be loaded by the CLI directly in order to be available inside of a config file. This means either bundling custom rules in a plugin or using the --rulesdir flag to specify the directory from which ESLint should load custom rules. Both approaches required some extra work to set up and were a frequent cause of frustration for our users.

With flat config, you can load custom rules directly in the config file. Because plugins are now objects directly in the config, you can easily create runtime plugins that exist only in your config file, such as:

import myrule from "./custom-rules/myrule.js";

export default [
    {
        files: ["**/*.js"],
        plugins: {
            custom: {
                rules: {
                    myrule
                }
            }
        },
        rules: {
            "custom/myrule": "error"
        }
    }
];

Here, a custom rule is imported as myrule and then a runtime plugin is created named custom to provide that rule to the config as custom/myrule.

As a result, we will be removing --rulesdir once the transition to flat config is complete.

Processors works in a similar way to eslintrc

The processor top-level key works mostly the same as in eslintrc, with the primary use case being to use a processor that is defined in a plugin, for example:

import markdown from "eslint-plugin-markdown";

export default [
    {
        files: ["**/*.md"],
        plugins: {
            markdown
        },
        processor: "markdown/markdown"
    }
];

This configuration object specifies that there is a processor called "markdown" contained in the plugin named "markdown" and will apply the processor to all files ending with .md.

The one addition in flat config is that processor can now also be an object containing both a preprocess() and a postprocess() method.

Organized linter options

In eslintrc, there were a couple of keys that related directly to how the linter operated, namely noInlineConfig and reportUnusedDisableDirectives. These have moved into the new linterOptions key but work exactly the same as in eslintrc. Here’s an example:

export default [
    {
        files: ["**/*.js"],
        linterOptions: {
            noInlineConfig: true,
            reportUnusedDisableDirectives: true
        }
    }
];

Shared settings are exactly the same

The top-level settings key behaves the exact same way as in eslintrc. You can define an object with key-value pairs that should be available to all rules. Here’s an example:

export default [
    {
        settings: {
            sharedData: "Hello"
        }
    }
];

Using predefined configs

ESLint has two predefined configurations for JavaScript:

js.configs.recommended - enables the rules that ESLint recommends everyone use to avoid potential errors
js.configs.all - enables all of the rules shipped with ESLint

To include these predefined configurations, install the @eslint/js package and then make any modifications to other properties in subsequent configuration objects:

import js from "@eslint/js";

export default [
    js.configs.recommended,
    {
        rules: {
            semi: ["warn", "always"]
        }
    }
];

Here, the eslint:recommended predefined configuration is applied first and then another configuration object adds the desired configuration for semi.

Backwards compatibility utility

As mentioned previously, we felt like there needed to be a good amount of backwards compatibility with eslintrc in order to ease the transition. The @eslint/eslintrc package provides a FlatCompat class that makes it easy to continue using eslintrc-style shared configs and settings within a flat config file. Here’s an example:

import { FlatCompat } from "@eslint/eslintrc";
import path from "path";
import { fileURLToPath } from "url";

// mimic CommonJS variables -- not needed if using CommonJS
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const compat = new FlatCompat({
    baseDirectory: __dirname
});

export default [

    // mimic ESLintRC-style extends
    ...compat.extends("standard", "example"),

    // mimic environments
    ...compat.env({
        es2020: true,
        node: true
    }),

    // mimic plugins
    ...compat.plugins("airbnb", "react"),

    // translate an entire config
    ...compat.config({
        plugins: ["airbnb", "react"],
        extends: "standard",
        env: {
            es2020: true,
            node: true
        },
        rules: {
            semi: "error"
        }
    })
];

Using the FlatCompat class allows you to continue using all of your existing eslintrc files while optimizing them for use with flat config. We envision this as a necessary transitional step to allow the ecosystem to slowly convert over to flat config.

Conclusion

The team spent a long time designing flat config so that it would both feel familiar to existing users and provide new functionality that would benefit everyone. We kept things like rules, settings, and processors the same while extending things like plugins, language options, and linter options to be more uniform. We think that flat config has found a good balance between these two poles and that you will enjoy using ESLint more once the new config system is generally available. In the meantime, the compatibility utility will allow you to continue using existing shared configs.

In the next part of this blog series, you’ll learn how to start using flat config today.

Updated (2024-08-12): Updated the predefined ESLint configurations for JavaScript.

ESLint's new config system, Part 1: Background

2022-08-03T00:00:00Z

When ESLint was first released in 2013, the config system was fairly simple. You could define the rules you wanted to enable or disable in a .eslintrc file. When a file was linted, ESLint would first look in the same directory as that file for a .eslintrc file and then continue up the directory hierarchy until reaching the root, merging configurations from all the .eslintrc files found along the way. This system, which we called the configuration cascade, allowed you to easily override rules for particular directories, something that JSHint wasn’t capable of doing. You could also add more configuration in the eslintConfig key inside of package.json.

Over the years, however, the config system grew into an unwieldy mess. That’s why in 2019 I proposed creating a new config system to make it easier to configure ESLint in a world where JavaScript projects are growing increasingly complex. A significant portion of the new config system has been merged into the main branch, and so it’s time to start learning about how you will configure ESLint in the future. But in order to do that, it’s helpful to take a look back and see how we got into the current state of things.

Incremental changes leading to maximum complexity

Looking back at how the current config system (called the eslintrc system) evolved, every step made logical sense for where we were at the time. ESLint has always operated on an incremental approach to development where we look at ways to improve what we already have instead of throwing things away to start over. The eslintrc system was no different.

The `extends` key

The first significant change to eslintrc was with the introduction of the extends key. The extends key, borrowed lovingly from JSHint, allowed users to import another configuration and then augment it, for example:

{
  "extends": ["./other-config.json"],
  "rules": {
    "semi": "warn"
  }
}

So assuming ./other-config.json had some configuration data, you could import that and then add your own rules settings on top of it. This turned out to be a great step forward for ESLint for a number of reasons.

First, extends actually preceded the idea of shareable configs that could be distributed via npm. It was during the implementation of extends that we realized shareable configs were possible. The files specified in extends were loaded via the Node.js require() function, so anything Node.js could load through that function could also work as a config to extend from.

Second, extends allowed us to implement eslint:recommended, the set of rules that we felt were important for everyone to enable. Originally ESLint had several rules enabled by default, but that became a burden for users. So we switched to having all rules off by default, which also was confusing for new users who didn’t see any rules. Adding eslint:recommended allowed us to make it explicit that you were including a bunch of rules we recommended but you could remove them if you didn’t want to.

In hindsight, if we had thought things through a little more, we would have removed the configuration cascade at this point. Introducing extends enabled a lot of the same use cases as the cascade, and keeping both turned out to be a mess that we would spend years trying to fix.

Personal configs

The next layer of complexity was added when people requested that we add the ability to have a personal config file at ~/.eslintrc. So we added an additional check: if we didn’t find a config file in the ancestry of the file location, then we would automatically look for a personal config file.

Multiple config file formats

As part of a refactor, we discovered that it would be trivial to allow different config file formats. Instead of forcing everyone to use a nonstandard .eslintrc file, we could formalize the JSON format as .eslintrc.json and also add support for YAML (.eslintrc.yml or .eslintrc.yaml) and JavaScript (.eslintrc.js). For backwards compatibility we continued to support .eslintrc because it was a trivial amount of code to keep around.

This also turned out, in hindsight, to not be a great idea. Adding a JavaScript config file format created an incompatibility between it and the non-JS formats: any JavaScript object could be passed into the config and available in rules. Because we didn’t properly validate the config to exactly match the non-JS formats, we ended up with some rules requiring regular expression objects to be passed in to be properly configured. While this could work in the JS config file format, the rules could not be properly configured in non-JS config files. Unfortunately, because plugin rules depended on this functionality, we couldn’t go back and fix it without breaking things.

Shareable configs and dependencies

Perhaps the biggest problem we faced early on was when npm decided to stop installing peer dependencies in v3. Prior to this point, we had recommended that shareable configs include any plugins they depended on as peer dependencies rather than regular dependencies. This was a quirk of the way that extends was implemented: using require().

Because shareable configs were data-only and couldn’t directly reference Node.js dependencies, require() would not automatically load direct dependencies into the path for ESLint to resolve them. Peer dependencies, on the other hand, worked perfectly by just using require() because those were installed in a location where the normal package lookup worked.

When npm v3 stopped installing peer dependencies by default, all of the shared configs relying on this behavior stopped working correctly. There is a long-running issue requesting that shareable configs be allowed to use dependencies directly, but the architecture of eslintrc just didn’t allow for it. We would have essentially had to recreate the entire require() functionality inside of ESLint to work around the way shareable configs were designed. We recommended that shareable configs create a post-install script to install their peer dependencies instead. Not ideal by any stretch of the imagination.

We added the --resolve-plugins-relative-to command line option to try and help with this problem, but it wasn’t enough. The most popular requests for help in our Discord #help channel have to do with improper resolution of plugins from config files.

npm eventually changed back to installing peer dependencies by default in v7, but by that point the damage on the ESLint ecosystem had been done.

The `root` key

As time went on, the config cascade continued to cause problems for users. Most frequently, people wouldn’t realize that they had a config file in an ancestor directory of the project they were working on. This would create confusion because they would be getting ESLint settings that they seemingly hadn’t configured.

To help with this problem we introduced the root property for configuration files. When root: true is specified in a config, the search for further config files doesn’t proceed to ancestor directories. This stopped a bit of the confusion and we ended up automatically including root: true in configs that ESLint generated via the old --init command to help users start off with the least amount of confusion.

The `overrides` key

ESLint continued to receive requests for more powerful ways to configure their projects. More specifically, there were requests to provide glob-based configs from within existing config files. This led to the creation of an overrides key that would let you further modify configurations for a specific subset of files that ESLint was linting. Here’s an example:

{
  "rules": {
    "quotes": ["error", "double"]
  },

  "overrides": [
    {
      "files": ["bin/*.js", "lib/*.js"],
      "excludedFiles": "*.test.js",
      "rules": {
        "quotes": ["error", "single"]
      }
    }
  ]
}

In this case, the JavaScript files in bin and lib prefer single quotes instead of the double quotes preferred everywhere else.

The overrides key with glob-based configuration turned out to be a much better way of accomplishing what the configuration cascade was attempting to do. Once again, in hindsight, this would have been the perfect time to try and remove the cascade…but we didn’t. And the complexity didn’t stop there.

Adding `extends` to `overrides`

The last step of eslintrc development was to add the extends key to overrides configurations, allowing users to inject additional config data into a glob-based config object, like this:

{
  "rules": {
    "quotes": ["error", "double"]
  },

  "overrides": [
    {
      "files": ["bin/*.js", "lib/*.js"],
      "excludedFiles": "*.test.js",
      "extends": ["eslint:recommended"],
      "rules": {
        "quotes": ["error", "single"]
      }
    }
  ]
}

This addition also introduced a lot of additional complexity because we had to figure out how to merge glob patterns between two different configs. The end result was that extends inside of an overrides config would use an AND operator to merge files and excludedFiles. If you’re not sure what exactly that means, you’re not alone. It’s confusing even to us.

The need for simplification

Around the new year of 2019, I was getting more concerned about the complexity of the eslintrc system. We were getting more and more questions about obscure error messages related to loading config files that couldn’t find other config files or plugins. Additionally, the team was collectively becoming afraid of touching anything to do with the config system. No one really understood all of the different permutations around calculating the final config for any given file. We had fallen into the trap that many software projects do: we kept adding new features without taking a a step back to look at the problem (and solution) holistically. This had led to an almost unmaintainable part of our codebase.

It was at this time that I did a thought experiment: what would the config system look like if I started from scratch, today, knowing everything that I now know about ESLint? What followed was the most contentious RFC proposal in the history of ESLint. At the time, the team was almost evenly split between those who wanted to throw away eslintrc and start from scratch and those who felt that eslintrc could be saved with more iterations. Ultimately, after 18 months of revisions and debate, we decided that it was time to embark on an entirely new config system built with today’s reality in mind.

The path forward

It’s now 2022 and we finally have the first implementation of the new config system released in v8.21.0. The new system, which we’ve nicknamed “flat config,” is designed to feel familiar to existing ESLint users while dramatically simplifying the process of setting up a config file. Flat config isn’t available through the CLI yet as we continue to work on bugs and gathering feedback, but it is available to developers who use the API directly. I’ll be discussing the design of flat config in part 2 of this series.

ESLint v8.21.0 released

2022-08-01T00:00:00Z

Highlights

ESLint will now print deprecation warnings for two changes that are coming in ESLint v9: First, rules with options must specify schemas. Second, rules must be defined using the object-style format that has been available since ESLint v2 rather than the legacy function-style format. See RFC85 for full details.
We took a big step toward ESLint’s new config system! The new FlatESLint class is now merged. Its API is not yet stable, and not all features are implemented yet, but it is accessible via the Node.js API for early testing. See RFC9 for the original design.

Features

7b43ea1 feat: Implement FlatESLint (#16149) (Nicholas C. Zakas)
92bf49a feat: improve the key width calculation in key-spacing rule (#16154) (Nitin Kumar)
c461542 feat: add new allowLineSeparatedGroups option to the sort-keys rule (#16138) (Nitin Kumar)
1cdcbca feat: add deprecation warnings for legacy API in RuleTester (#16063) (Nitin Kumar)

Bug Fixes

0396775 fix: lines-around-comment apply allowBlockStart for switch statements (#16153) (Nitin Kumar)

Documentation

2aadc93 docs: add anchors to headings inside docs content (#16134) (Strek)

Chores

8892511 chore: Upgrade to Espree 9.3.3 (#16173) (Brandon Mills)
1233bee chore: switch to eslint-plugin-node’s maintained fork (#16150) (唯然)
97b95c0 chore: upgrade puppeteer v13 (#16151) (唯然)

ESLint v8.20.0 released

2022-07-16T00:00:00Z

Highlights

ESLint now catches exceptions thrown by preprocessors and reports them as lint errors. This matches how ESLint already handled parser errors. Previously, exceptions thrown by preprocessors would crash ESLint.

Features

ca83178 feat: catch preprocess errors (#16105) (JounQin)

Bug Fixes

30be0ed fix: no-warning-comments rule escapes special RegEx characters in terms (#16090) (Lachlan Hunt)
bfe5e88 fix: ignore spacing before ] and } in comma-spacing (#16113) (Milos Djermanovic)

Documentation

845c4f4 docs: Add website team details (#16115) (Nicholas C. Zakas)
5a0dfdb docs: Link to blog post in no-constant-binary-expression (#16112) (Jordan Eldredge)
bc692a9 docs: remove install command (#16084) (Strek)
49ca3f0 docs: don’t show toc when content not found (#16095) (Amaresh S M)
ba19e3f docs: enhance 404 page UI (#16097) (Amaresh S M)
a75d3b4 docs: remove unused meta.docs.category field in working-with-rules page (#16109) (Brandon Scott)
cdc0206 docs: add formatters page edit link (#16094) (Amaresh S M)
4d1ed22 docs: preselect default theme (#16098) (Strek)
4b79612 docs: add missing correct/incorrect containers (#16087) (Milos Djermanovic)
09f6acb docs: fix UI bug on rules index and details pages (#16082) (Deepshika S)
f5db264 docs: remove remaining duplicate rule descriptions (#16093) (Milos Djermanovic)
32a6b2a docs: Add scroll behaviour smooth (#16056) (Amaresh S M)

Chores

bbf8df4 chore: Mark autogenerated release blog post as draft (#16130) (Nicholas C. Zakas)
eee4306 chore: update internal lint dependencies (#16088) (Bryan Mishkin)
9615a42 chore: update formatter examples template to avoid markdown lint error (#16085) (Milos Djermanovic)
62541ed chore: fix markdown linting error (#16083) (唯然)

Interesting bugs caught by no-constant-binary-expression

2022-07-06T00:00:00Z

In ESLint v8.14.0 I contributed a new core rule called no-constant-binary-expression which has surprised me with the wide variety of subtle and interesting bugs it has been able to detect.

In this post I’ll explain what the rule does and share some examples of real bugs it has detected in popular open source projects such as Material UI, Webpack, VS Code, and Firefox as well as a few interesting bugs that it found internally at Meta. I hope these examples will convince you to try enabling the rule in the projects you work on!

What does `no-constant-binary-expression` do?

The rule checks for comparisons (==, !==, etc) where the outcome cannot vary at runtime, and logical expressions (&&, ??, ||) which will either always or never short-circuit.

For example:

+x == null will always be false, because + will coerce x into a number, and a number is never nullish.
{ ...foo } || DEFAULT will never return DEFAULT because objects are always truthy.

Both of these are examples of expressions that look like they can affect the way the program evaluates, but in reality, do not.

This rule originally started as just an attempt to detect unnecessary null checks. However, as I worked on it, I realized useless null checks were just a special case of a broader category: useless code. Eventually it clicked for me: developers don’t intend to write useless code, and code that does not match the developer’s intent is by definition a bug. Therefore, any useless code you can detect is a bug.

This realization was confirmed for me when I ran the first version of the rule against our code base at Meta, and it detected a wide variety of subtle and interesting bugs which had made it through code review.

Real world bugs found with `no-constant-binary-expressions`

In this section I’ll share a number of types of bugs that this rule can catch. Each includes at least one concrete example detected in a popular open source project. My choice to include real examples here is not to shame anyone or any project, but to drive home the fact that these are errors that any team can easily make.

Confusing operator precedence

The most common class of bug the rule finds is places where developers misunderstood the precedence of operators, particularly unary operators like !, + and typeof.

if (!whitelist.has(specifier.imported.name) == null) {
  return;
}

From Material UI (also: VS Code 1, 2, Webpack, Mozilla)

Confusing `??` and `||` precedence

When trying to define default values, people get confused with expressions like a === b ?? c and assume it will be parsed as a === (b ?? c). When in actuality it will be parsed as (a === b) ?? c.

shouldShowWelcome() {
  return this.viewModel?.welcomeExperience === WelcomeExperience.ForWorkspace ?? true;
}

From VS Code

Aside: Observing how frequently developers get confused by operator precedence inspired me to experiment with a VS Code extension to visually clarify how precedence gets interpreted.

Expecting objects to be compared by value

Developers coming from other languages where structures are compared by value, rather than by reference, can easily fall into the trap of thinking they can do things like test if an object is empty by comparing with a newly created empty object. Or course in JavaScript, objects are compared by reference, and no value can ever be equal to a newly constructed object literal.

In this example, hasData will always be set to true because data can never be referentially equal to a newly created object.

hasData = hasData || data !== {};

From Firefox (also: Firefox)

Expecting empty objects to be `false` or `null`

Another common categrory of JavaScript error is expecting empty objects to be nullish or falsy. This is likely an easy mistake to make for folks coming from a language like Python where empty lists and dictionaries are falsy.

const newConfigValue = { ...configProfiles } ?? {};

From VS Code (also: VS Code 1, 2)

Is it `>=` or `=>`?

I’ve only seen this particular typo once, but I wanted to include it because it’s a great example of the unexpected types of bugs this rule can catch.

Here, the developer meant to test if a value was greater than or equal to zero (>= 0), but accidentally reversed the order of the characters and created an arrow function that returned 0 && startWidth <= 1!

assert(startWidth => 0 && startWidth <= 1);

From Mozilla

Other errors caught by `no-constant-binary-expression`

The above five categories of errors are not exhaustive. When I originally ran the first version of this rule on our (very) large monorepo at Meta, it found over 500 issues. While many fell into the categories outlined above, there was also a long-tail of other interesting bugs. Some highlights include:

Thinking || allows for set operations: states.includes('VALID' || 'IN_PROGRESS')
Thinking primitive functions pass through nulls: Number(x) == null
Not knowing primitive constructors return boxed primitives: new Number(x) === 10

I never would have set out to lint for these specific issues individually, but by simply trying to identify anything “useless” we were able to find and correct them.

Conclusion

As you’ve now seen no-constant-binary-expression is capable of detecting a variety of different types of bugs. The rule accomplishes this not because it’s programmed to look for those specific issues, but because all those bugs have one thing in common: they manifest as useless code. Because developers generally don’t intend to write useless code, detecting useless code generally results in detecting bugs.

If you’ve found these examples compelling, please consider enabling no-constant-binary-expression in your ESLint config:

// eslintrc
module.exports = {
  rules: {
    // Requires eslint >= v8.14.0
    "no-constant-binary-expression": "error"
  }
}

If you do, and it finds bugs, I’d love to hear about them!

Thanks to Brad Zacher for the original observation which inspired this work and the suggestion to propose it as a new core rule. And thanks to Milos Djermanovic for significant contributions during code review.

ESLint v8.19.0 released

2022-07-01T00:00:00Z

Highlights

The no-restricted-imports rule now supports the importNames option for more granular control of imports when matching modules with patterns.

Features

7023628 feat: add importNames support for patterns in no-restricted-imports (#16059) (Brandon Scott)
472c368 feat: fix handling of blockless with statements in indent rule (#16068) (Milos Djermanovic)

Bug Fixes

fc81848 fix: throw helpful exception when rule has wrong return type (#16075) (Bryan Mishkin)

Documentation

3ae0574 docs: Remove duplicate rule descriptions (#16052) (Amaresh S M)
f50cf43 docs: Add base href to each page to fix relative URLs (#16046) (Nicholas C. Zakas)
ae4b449 docs: make logo link clickable on small width screens (#16058) (Milos Djermanovic)
280f898 docs: use only fenced code blocks (#16044) (Milos Djermanovic)
f5d63b9 docs: add listener only if element exists (#16045) (Amaresh S M)
8b639cc docs: add missing migrating-to-8.0.0 in the user guide (#16048) (唯然)
b8e68c1 docs: Update release process (#16036) (Nicholas C. Zakas)
6d0cb11 docs: remove table of contents from markdown text (#15999) (Nitin Kumar)

Chores

e884933 chore: use github-slugger for markdown anchors (#16067) (Strek)
02e9cb0 chore: revamp carbon ad style (#16078) (Amaresh S M)
b6aee95 chore: remove unwanted comments from rules markdown (#16054) (Strek)
6840940 chore: correctly use .markdownlintignore in Makefile (#16060) (Bryan Mishkin)
48904fb chore: add missing images (#16017) (Amaresh S M)
910f741 chore: add architecture to nav (#16039) (Strek)
9bb24c1 chore: add correct incorrect in all rules doc (#16021) (Deepshika S)
5a96af8 chore: prepare versions data file (#16035) (Nicholas C. Zakas)
50afe6f chore: Included githubactions in the dependabot config (#15985) (Naveen)
473411e chore: add deploy workflow for playground (#16034) (Milos Djermanovic)
a30b66c chore: fix print style (#16025) (Amaresh S M)
f4dad59 chore: add noindex meta tag (#16016) (Milos Djermanovic)
db387a8 chore: fix sitemap (#16026) (Milos Djermanovic)
285fbc5 chore: remove TOC from printable (#16020) (Strek)
8e84c21 chore: remove ligatures from fonts (#16019) (Strek)

ESLint v8.18.0 released

2022-06-17T00:00:00Z

Highlights

Per-rule performance report now includes time spent in create() of rules. This time is added to the time spent in the listeners.

Features

a6273b8 feat: account for rule creation time in performance reports (#15982) (Nitin Kumar)

Bug Fixes

f364d47 fix: Make no-unused-vars treat for…of loops same as for…in loops (#15868) (Alex Bass)

Documentation

4871047 docs: Update analytics, canonical URL, ads (#15996) (Nicholas C. Zakas)
cddad14 docs: Add correct/incorrect containers (#15998) (Nicholas C. Zakas)
b04bc6f docs: Add rules meta info to rule pages (#15902) (Nicholas C. Zakas)
1324f10 docs: unify the wording referring to optional exception (#15893) (Abdelrahman Elkady)
ad54d02 docs: add missing trailing slash to some internal links (#15991) (Milos Djermanovic)
df7768e docs: Switch to version-relative URLs (#15978) (Nicholas C. Zakas)
21d6479 docs: change some absolute links to relative (#15970) (Milos Djermanovic)
f31216a docs: Update README team and sponsors (ESLint Jenkins)

ed49f15 build: remove unwanted parallel and image-min for dev server (#15986) (Strek)

Chores

f6e2e63 chore: fix ‘replaced by’ rule list (#16007) (Milos Djermanovic)
d94dc84 chore: remove unused deprecation warnings (#15994) (Francesco Trotta)
cdcf11e chore: fix versions link (#15995) (Milos Djermanovic)
d2a8715 chore: add trailing slash to pathPrefix (#15993) (Milos Djermanovic)
58a1bf0 chore: tweak URL rewriting for local previews (#15992) (Milos Djermanovic)
80404d2 chore: remove docs deploy workflow (#15984) (Nicholas C. Zakas)
71bc750 chore: Set permissions for GitHub actions (#15971) (Naveen)
90ff647 chore: avoid generating subdirectories for each page on new docs site (#15967) (Milos Djermanovic)

ESLint v8.17.0 released

2022-06-03T00:00:00Z

Highlights

The no-use-before-define rule has a new option allowNamedExports.

Features

55319e1 feat: fix indent bug with semicolon-first style (#15951) (Milos Djermanovic)
f6d7920 feat: add allowNamedExports option to no-use-before-define (#15953) (Milos Djermanovic)

Bug Fixes

54c0953 fix: cleanup typos (#15939) (Nick Schonning)
845a7af fix: typo ocatal -> octal (#15940) (Nick Schonning)

Documentation

b915018 docs: Update website UI to latest (#15944) (Nicholas C. Zakas)
f0bb609 docs: Update Exponentiation operator MDN link (#15960) (Pranjal Jain)
baa0153 docs: Use correct past tense “left” instead of “leaved” (#15950) (Frederik Braun)
1351a9b docs: Add Resources section to rule pages (#15901) (Nicholas C. Zakas)
68cf0fb docs: cleanup typos (#15936) (Nick Schonning)
13b62ae docs: use-dart-sass instead of node-sass (#15912) (Deepshika S)
c81c5d6 docs: add social media links (#15920) (Deepshika S)
0d6a50b docs: fix openjs link (#15917) (Amaresh S M)
54910f5 docs: display version in mobile view (#15909) (Amaresh S M)

Chores

da694b9 chore: avoid theme flashes (#15927) (Strek)
f836743 chore: Use build hook for docs deploy (#15945) (Nicholas C. Zakas)
ce035e5 test: cleanup typos (#15937) (Nick Schonning)
10249ad chore: use addEventListener instead of addListener (#15923) (Amaresh S M)
5f5c1fb chore: lint eleventy config file (#15904) (Milos Djermanovic)
8513d37 chore: update Rule typedefs (#15915) (Milos Djermanovic)
55534f1 test: ensure no-restricted-imports works with NodeJS imports (#15907) (Nick Mazuk)

ESLint v8.16.0 released

2022-05-20T00:00:00Z

Highlights

The no-misleading-character-class rule now provides suggestions for some of the problems reported by this rule.

Features

cab0c22 feat: add Unicode flag suggestion in no-misleading-character-class (#15867) (Milos Djermanovic)
38ae956 feat: check Unicode code point escapes in no-control-regex (#15862) (Milos Djermanovic)
ee69cd3 feat: Update global variables (#15871) (Sébastien Règne)

Bug Fixes

3f09aab fix: function-paren-newline crash on “new new Foo();” (#15850) (coderaiser)

Documentation

050d5f4 docs: Static further reading links (#15890) (Nicholas C. Zakas)
36287c0 docs: fix absolute paths in related rules shortcode to work from /docs (#15892) (Milos Djermanovic)
90b6990 docs: fix absolute links in rule macro to work from /docs (#15891) (Milos Djermanovic)
f437249 docs: Adjust docs site path prefix (#15889) (Nicholas C. Zakas)
6e16025 docs: update ‘Related Rules’ and ‘Further Reading’ in remaining rules (#15884) (Milos Djermanovic)
1d39f69 docs: remove confusing examples for no-mixed-operators (#15875) (Milos Djermanovic)
3071d76 docs: Fix some grammar issues (#15837) (byodian)

Chores

1768d0d chore: upgrade @eslint/eslintrc@1.3.0 (#15903) (Milos Djermanovic)
c686e4c chore: Add deploy workflow for docs site (#15894) (Nicholas C. Zakas)
c7894cd chore: enable some rules from eslint-plugin-unicorn internally (#15878) (Bryan Mishkin)
ea65cb5 chore: upgrade eslint-plugin-eslint-plugin@^4.2.0 (#15882) (唯然)
cc29c69 chore: Upgrade official GitHub actions to latest versions (#15880) (Darius Dzien)
5891c75 chore: Refactor rule docs format (#15869) (Nicholas C. Zakas)

ESLint v8.15.0 released

2022-05-06T00:00:00Z

Highlights

The no-underscore-dangle rule has a new option enforceInClassFields.

Features

ab37d3b feat: add enforceInClassFields option to no-underscore-dangle (#15818) (Roberto Cestari)

Bug Fixes

8bf9440 fix: “use strict” should not trigger strict mode in ES3 (#15846) (Milos Djermanovic)

Documentation

28116cc docs: update AST node names link in no-restricted-syntax (#15843) (Milos Djermanovic)
272965f docs: fix h1 heading on formatters page (#15834) (Milos Djermanovic)
a798166 docs: update example for running individual rule tests (#15833) (Milos Djermanovic)
57e732b docs: mark SourceCode#getJSDocComment deprecated in working-with-rules (#15829) (Milos Djermanovic)
9a90abf docs: update docs directory in working-with-rules (#15830) (Milos Djermanovic)
810adda docs: add more examples for prefer-object-spread (#15831) (coderaiser)
06b1edb docs: clarify no-control-regex rule (#15808) (Milos Djermanovic)
9ecd42f docs: Fixed typo in code comment (#15812) (Addison G)
de992b7 docs: remove links to 2fa document (#15804) (Milos Djermanovic)
5222659 docs: fix ‘Related Rules’ heading in no-constant-binary-expression (#15799) (Milos Djermanovic)
e70ae81 docs: Update README team and sponsors (ESLint Jenkins)

Chores

1ba6a92 chore: upgrade @eslint/eslintrc@1.2.3 (#15847) (Milos Djermanovic)
8167aa7 chore: bump version of minimatch due to security issue PRISMA-2022-0039 (#15774) (Jan Opravil)
b8995a4 chore: Implement docs site (#15815) (Nicholas C. Zakas)
6494e3e chore: update link in codeql-analysis.yml (#15817) (Milos Djermanovic)
36503ec chore: enable no-constant-binary-expression in eslint-config-eslint (#15807) (唯然)

ESLint v8.14.0 released

2022-04-22T00:00:00Z

Highlights

One new rule has been added: no-constant-binary-expression

Features

ab6363d feat: Add rule no-constant-binary-expression (#15296) (Jordan Eldredge)

Bug Fixes

35fa1dd fix: allow project paths to have URL-encoded characters (#15795) (Milos Djermanovic)
413f1d5 fix: update astUtils.isDirectiveComment with globals and exported (#15775) (Milos Djermanovic)

c2407e8 build: add node v18 (#15791) (唯然)

Chores

735458c chore: add static frontmatter to no-constant-binary-expression docs (#15798) (Milos Djermanovic)
db28f2c chore: Add static frontmatter to docs (#15782) (Nicholas C. Zakas)
3bca59e chore: markdownlint autofix on commit (#15783) (Nicholas C. Zakas)

ESLint v8.13.0 released

2022-04-08T00:00:00Z

Features

274acbd feat: fix no-eval logic for this in arrow functions (#15755) (Milos Djermanovic)

Bug Fixes

97b57ae fix: invalid operator in operator-assignment messages (#15759) (Milos Djermanovic)

Documentation

c32482e docs: Typo in space-infix-ops docs (#15754) (kmin-jeong)
f2c2d35 docs: disambiguate types FormatterFunction and LoadedFormatter (#15727) (Francesco Trotta)

Chores

bb4c0d5 chore: Refactor docs to work with docs.eslint.org (#15744) (Nicholas C. Zakas)
d36f12f chore: remove lib/init from eslint config (#15748) (Milos Djermanovic)
a59a4e6 chore: replace trimLeft/trimRight with trimStart/trimEnd (#15750) (Milos Djermanovic)

ESLint v8.12.0 released

2022-03-25T00:00:00Z

Features

685a67a feat: fix logic for top-level this in no-invalid-this and no-eval (#15712) (Milos Djermanovic)

Chores

18f5e05 chore: padding-line-between-statements remove useless additionalItems (#15706) (Martin Sadovy)

ESLint v8.11.0 released

2022-03-11T00:00:00Z

Highlights

The no-unused-vars rule has a new destructuredArrayIgnorePattern option.

Features

800bd25 feat: add destructuredArrayIgnorePattern option in no-unused-vars (#15649) (Nitin Kumar)
8933fe7 feat: Catch undefined and Boolean() in no-constant-condition (#15613) (Jordan Eldredge)
f90fd9d feat: Add ESLint favicon to the HTML report document (#15671) (Mahdi Hosseinzadeh)
57b8a57 feat: valid-typeof always ban undefined (#15635) (Zzzen)

Bug Fixes

6814922 fix: escaping for square brackets in ignore patterns (#15666) (Milos Djermanovic)
c178ce7 fix: extend the autofix range in comma-dangle to ensure the last element (#15669) (Milos Djermanovic)

Documentation

c481cec docs: add fast-eslint-8 to atom integrations (userguide) (#15695) (db developer)
d2255db docs: Add clarification about eslint-enable (#15680) (dosisod)
8b9433c docs: add object pattern to first section of computed-property-spacing (#15679) (Milos Djermanovic)
de800c3 docs: link to minimatch docs added. (#15688) (Gaurav Tewari)
8f675b1 docs: sort-imports add single named import example (#15675) (Arye Eidelman)

Chores

385c9ad chore: rm trailing space in docs (#15689) (唯然)

ESLint v8.10.0 released

2022-02-25T00:00:00Z

Highlights

The no-shadow rule has a new ignoreOnInitialization option.
The no-confusing-arrow rule has a new onlyOneSimpleParam option.

Features

6e2c325 feat: Add ignoreOnInitialization option to no-shadow rule (#14963) (Soufiane Boutahlil)
115cae5 feat: --debug prints time it takes to parse a file (#15609) (Bartek Iwańczuk)
345e70d feat: Add onlyOneSimpleParam option to no-confusing-arrow rule (#15566) (Gautam Arora)

Bug Fixes

cdc5802 fix: Avoid __dirname for built-in configs (#15616) (DoZerg)
ee7c5d1 fix: false positive in camelcase with combined properties (#15581) (Nitin Kumar)

Documentation

1005bd5 docs: update CLA information (#15630) (Nitin Kumar)
5d65c3b docs: Fix typo in no-irregular-whitespace (#15634) (Ryota Sekiya)
b93af98 docs: add links between rules about whitespace around block curly braces (#15625) (Milos Djermanovic)
ebc0460 docs: update babel links (#15624) (Milos Djermanovic)

Chores

7cec74e chore: upgrade @eslint/eslintrc@1.2.0 (#15648) (Milos Djermanovic)
11c8580 chore: read ESLINT_MOCHA_TIMEOUT env var in Makefile.js (#15626) (Piggy)
bfaa548 test: add integration tests with built-in configs (#15612) (Milos Djermanovic)
39a2fb3 perf: fix lazy loading of core rules (#15606) (Milos Djermanovic)
3fc9196 chore: include tests/conf in test runs (#15610) (Milos Djermanovic)

Paying contributors, sponsoring projects, and more: ESLint's 2022 spending plan

2022-02-23T00:00:00Z

In our last update on paying contributors, we noted some of the successes and challenges we had as a team. At that time, we were still trying to figure out ESLint’s model for sustainability. Having money to spend is one thing but knowing how to best use that money is another. Because we didn’t have enough money to pay anyone full time, we tried one maintainer at part time, and that didn’t work. After that experiment, we decided to regroup and reevaluate, ultimately deciding to use a per-hour payment system for team members.

Once we settled into the per-hour system, that also gave us information on how many hours each month people were spending on the project. That, in turn, showed us how much money we actually needed each month to continue maintaining ESLint. As a result of that information, we have arrived at a system that we are very pleased with.

The guiding principle

Before explaining how ESLint is using the money it collects now, it helps to take a step back to understand the guiding principles upon which this approach is based. Each project has different goals for why they are raising money and how it should be spent. For many projects, the goal is to allow the maintainer(s) to work full time on the project. That is a worthy goal provided that the maintainers actually want to work full time on the project. This is a narrow approach to distributing funds in that most or all of the money goes to one or a few people.

On ESLint, we discovered that we didn’t have any team members interested in working on the project full time. So we thought: what if we went in the complete opposite direction? Given that we know people will only work part time, and probably just in their spare time, how could we distribute the funds as widely as possible for the maximum positive impact?

When we asked ourselves this question, we realized that we were circling around a common theme: anything that benefits the ESLint ecosystem is worth supporting financially. The first and most obvious thing that benefits the ecosystem is having people maintaining ESLint, so we clearly need to make sure people are paid fairly for spending their time working on the project. But what else benefits the ecosystem? Well, ESLint is built on top of a bunch of dependencies, and we’d like to support those projects, so what if we donated some of our funds to those projects? There’s also a wide range of plugins, parsers, and extensions that help fuel use of ESLint, so what if we started sponsoring some of these projects as well? And we also get a bunch of contributions from outside contributors…what if we paid them?

So by aligning around the idea that anything that benefits the ESLint ecosystem is worth funding, we were able to find ways to spread the money we collected more widely, and we’re excited to share the results.

How we are spending our money now

In general, we regularly spend money on the following things.

Paying team members per hour

Each month, all ESLint team members can submit an invoice for the number of hours they worked on the project. Anything they do on the project counts, whether that is writing code, writing documentation, triaging issues, participating in our Discord server, attending meetings on behalf of ESLint, contributing to our upstream dependencies, and so on. All contributions to an open source project are valuable, and we feel like compensating team members for any time they spend on the project is the right thing to do.

Right now, the per-hour rate for Technical Steering Committee (TSC) members and Reviewers is $80/hour; the per-hour rate for Committers is $50/hour.

The contributor pool

One of the things we struggled with was how to fairly pay outside contributors for working on ESLint. We didn’t think a standard per-hour rate made much sense because 1) people might contribute without knowing to track their hours ahead of time and 2) trusting people you don’t know to accurately report their hours spend is a system that is too easy to exploit. Still, we felt like it wasn’t fair for us to pay for team member contributions but not for outside contributions, and so we created the contributor pool.

Each month, we set aside $1,000 specifically to give to outside contributors for any contributions to ESLint. The TSC reviews outside contributions at the end of each month and awards at least $100 to every outside contributor who has made a non-trivial contribution to ESLint. Once again, these contributions are not limited to coding, but can be anything that positively impacts the project. The contributors don’t need to apply ahead of time or ask for permission; if you make a significant contribution, you’ll get an email from the TSC letting you know how to collect your payment.

In 2021, we awarded over $6,000 to outside contributors, and we look forward to awarding more in 2022. The bottom line here: if you make any non-trivial contribution to ESLint, you will get paid for it.

Supporting our dependencies

As we announced in 2020, we actively seek out and donate to our dependencies. In general, any project we directly depend on that has an Open Collective account will be considered to receive a donation from ESLint. We are currently supporting five of our dependencies with monthly donations of $150:

Ajv is a JSON schema validator that ESLint uses to validate configuration.
Eleventy is a Node.js-based static site generator that we use to create eslint.org.
Sindre Sorhus is a prolific open source developer, and ESLint uses several of his modules, including chalk, globals, import-fresh, strip-ansi, and strip-json-comments.
debug is a small tool ESLint uses to output debugging messages when you use the --debug flag.
lint-staged is a simple precommit hook manager that makes it easy to setup linting in your development process.

We think it’s important for open source projects that receive a lot of donations to take care of their dependencies. After all, if your project couldn’t exist without those dependencies, then they deserve your support.

You can always check to see which projects ESLint is supporting on our Open Collective page.

Supporting the community

Once we started supporting our upstream dependencies, we thought, what about the downstream dependencies? There are a lot of projects related to ESLint that enrich the ESLint ecosystem, whether that be a different set of rules, a custom parser, or anything that makes ESLint better to use. We are currently donating $150 per month to these projects:

typescript-eslint is the plugin that makes ESLint work with TypeScript.
eslint-plugin-import is a plugin to help you manage your module imports.
eslint-plugin-jsx-a11y is a plugin to help you ensure your JSX code is accessible.

Going forward, we are looking to continue supporting community projects like these. The strength of ESLint is in the ecosystem built by you, and we want to support as much of that ecosystem as possible.

Big projects

The last way we decided to spend money is on what we playfully called “big projects.” These are projects that take a lot of time and effort, and that the team doesn’t have the time, interest, or expertise to accomplish on our own. Every project has a backlog of tasks that seem too big to ever accomplish, and we realized that we could start making our way through that list by hiring professionals to do the work.

The first of our big projects is an ambitious project to redesign the ESLint website. We had wanted to redesign our website for several years, and tried at least three separate times to do it in the spirit of open source, with volunteers and designing by consensus. Each of those times the efforts failed, and so we decided it was time to hire some folks to help us out.

The entire scope of the project is fairly large and includes:

A brand design including a logo refresh
A new website design that explains more about what ESLint is and how people use it
Separating the documentation into its own website that is easier to navigate
Separating the demo into its own single-page application to make it easier to maintain and deploy
Rewriting and updating our documentation (from scratch)
Translating our documentation into different languages

So far, we have finished step 1 and are getting close to finishing step 2. To do this, we hired:

JellyPepper for the brand refresh and visual design of the website.
Gavin Barnett to design our new blog images.
Sara Soueidan to implement the new website, documentation site, and demo skeleton.
Cassie Evans to implement a custom homepage animation.

The total cost of this effort has come to about $46,000 and we are thrilled with how everything has gone. This is a perfect example of where hiring professionals to do the work allowed us to move faster and (soon!) improve the website experience for all ESLint users.

Wrapping up

It took us a while to figure out the right way to use our sponsorship money, but now that we have, we think we’ve found the best way to sustain ESLint for the future. Making sure that everyone gets paid for non-trivial contributions was a goal we had from the start and we are happy that we finally figured out a way to do that.

Additionally, moving to a model where we share some of our funds with both our dependencies and other ecosystem projects feels more in the spirit of open source. We are an interconnected ecosystem where projects mix and reuse other projects to create even more interesting projects. Just as we would consider contributing code to projects that help us, we also need to consider donating money to those projects. The ESLint team feels grateful for the funding we have received and equally grateful to our dependencies without which ESLint couldn’t exist. We hope that this model will spread to other open source projects as well.

And last, we intend to continue hiring professionals to work on big projects. There are a lot of different aspects to running an open source project, and expecting volunteers to handle all of those aspects in unrealistic. We’ve had a great experience on the website project (which should be completed in the next few months) and we’ll be looking for other ways to create more value for the ESLint community going forward.

ESLint v8.9.0 released

2022-02-11T00:00:00Z

Highlights

New es2022 environment has been added. When enabled, it adds all ECMAScript 2022 globals (which are currently the same as ECMAScript 2021 globals) and automatically sets the ecmaVersion parser option to 13. Previously, we used to add new ES environments only if they contain new globals compared to previous years. New es2016, es2018, and es2019 environments have also been added to fill in the gaps between years.
eslint-scope has been updated to ignore "use strict" directives in ES3 code.
eslint-visitor-keys package now contains built-in TypeScript declarations.

Features

68f64a9 feat: update eslint-scope to ignore "use strict" directives in ES3 (#15595) (Milos Djermanovic)
db57639 feat: add es2016, es2018, es2019, and es2022 environments (#15587) (Milos Djermanovic)
2dc38aa feat: fix bug with arrow function return types in function-paren-newline (#15541) (Milos Djermanovic)
6f940c3 feat: Implement FlatRuleTester (#15519) (Nicholas C. Zakas)

Documentation

570a036 docs: add one-var example with for-loop initializer (#15596) (Milos Djermanovic)
417191d docs: Remove the $ prefix in terminal commands (#15565) (Andreas Lewis)
389ff34 docs: add missing Variable#scope property in the scope manager docs (#15571) (Milos Djermanovic)
f63795d docs: no-eval replace dead link with working one (#15568) (rasenplanscher)
0383591 docs: Remove old Markdown issue template (#15556) (Brandon Mills)
a8dd5a2 docs: add ‘when not to use it’ section in no-duplicate-case docs (#15563) (Milos Djermanovic)
1ad439e docs: add missed verb in docs (#15550) (Jeff Mosawy)

Chores

586d45c chore: Upgrade to espree@9.3.1 (#15600) (Milos Djermanovic)
623e1e2 chore: Upgrade to eslint-visitor-keys@3.3.0 (#15599) (Milos Djermanovic)
355b23d chore: fix outdated link to Code of Conduct in PR template (#15578) (Rich Trott)
b10fef2 ci: use Node 16 for browser test (#15569) (Milos Djermanovic)
92f89fb chore: suggest demo link in bug report template (#15557) (Brandon Mills)

ESLint v8.8.0 released

2022-01-28T00:00:00Z

Highlights

Suppressed Messages

Suppressed messages are lint messages (errors and warnings) that were suppressed by eslint-disable, eslint-disable-line and eslint-disable-next-line comments.

ESLint API now provides information about suppressed lint messages. This information is available to custom formatters and API users as a new property suppressedMessages (array of SuppressedLintMessage objects) on LintResult objects.

Features

5d60812 feat: implement rfc 2021-suppression-support (#15459) (Yiwei Ding)

Documentation

5769cc2 docs: fix relative link (#15544) (Nick Schonning)
ccbc35f docs: trimmed rules h1s to just be rule names (#15514) (Josh Goldberg)
851f1f1 docs: fixed typo in comment (#15531) (Jiapei Liang)
7d7af55 docs: address upcoming violation of markdownlint rule MD050/strong-style (#15529) (David Anson)

ESLint v8.7.0 released

2022-01-15T00:00:00Z

Highlights

The functionality behind eslint --init has been pulled into a standalone @eslint/create-config package. Now, you can initialize ESLint in a new project with npm init @eslint/config, npx @eslint/create-config, or yarn create @eslint/config.
Several rules gained support for arbitrary module namespace names.

Features

19ad061 feat: no-restricted-imports support casing (#15439) (gfyoung)
564ecdb feat: Support arbitrary module namespace names in no-restricted-imports (#15491) (Milos Djermanovic)
968a02a feat: Support arbitrary module namespace names in no-useless-rename (#15493) (Milos Djermanovic)
0d2b9a6 feat: move eslint --init to @eslint/create-config (#15150) (唯然)
127f524 feat: false negative with property option in id-match (#15474) (Nitin Kumar)
359b2c1 feat: Support arbitrary module namespace names in the camelcase rule (#15490) (Milos Djermanovic)
3549571 feat: Support arbitrary module namespace names in the quotes rule (#15479) (Milos Djermanovic)
5563c45 feat: Support arbitrary module namespace names in keyword-spacing (#15481) (Milos Djermanovic)
fd3683f feat: Support arbitrary module namespace names in no-restricted-exports (#15478) (Milos Djermanovic)

Bug Fixes

a8db9a5 fix: no-invalid-this false positive in class field initializer (#15495) (Milos Djermanovic)
02d6426 fix: Correctly consume RuleTester statics (#15507) (Brad Zacher)
db15802 fix: Add property fatalErrorCount to ignored file results (#15520) (Francesco Trotta)
03ac8cf fix: Prevent false positives with no-constant-condition (#15486) (Jordan Eldredge)

Documentation

f50f849 docs: Update CLI docs to prefer local install (#15513) (Nicholas C. Zakas)
0469eb1 docs: Update shell code fences for new website (#15522) (Olga)

Chores

369fb1b chore: Upgrade to eslint-visitor-keys@3.2.0 (#15526) (Brandon Mills)
ba6317b ci: remove master branch from CI configs (#15501) (Milos Djermanovic)
79b6340 chore: fixed typo in client-Engine (#15497) (Abhay Gupta)
6278281 chore: switch new syntax issue template to forms (#15480) (Nitin Kumar)

ESLint v8.6.0 released

2021-12-31T00:00:00Z

Highlights

ESLint v8.6.0 allows rule lists or descriptions in eslint-disable-next-line comments to wrap lines:

/* eslint-disable-next-line no-console --
 * Here's a very long description about why this configuration is necessary
 * along with some additional information.
 */
console.log('hello');

Features

6802a54 feat: handle logical assignment in no-self-assign (#14152) (Zzzen)
3b38018 feat: allow to define eslint-disable-next-line in multiple lines (#15436) (Nitin Kumar)
9d6fe5a feat: false negative with onlyDeclarations + properties in id-match (#15431) (Nitin Kumar)

Documentation

6c4dee2 docs: Document homedir is a configuration root (#15469) (Bas Bosman)
51c37b1 docs: consistency changes (#15404) (Bas Bosman)
775d181 docs: Mention character classes in no-useless-escape (#15421) (Sebastian Simon)

Chores

3a384fc chore: Upgrade espree to 9.3.0 (#15473) (Brandon Mills)
1443cc2 chore: Update blogpost.md.ejs (#15468) (Nicholas C. Zakas)
28e907a refactor: remove unused parameter in linter.js (#15451) (Milos Djermanovic)
eaa08d3 test: add tests for allowReserved parser option with flat config (#15450) (Milos Djermanovic)

ESLint v8.5.0 released

2021-12-17T00:00:00Z

Highlights

One new rule has been added: prefer-object-has-own.
The prefer-regex-literals rule now provides suggestions.

Features

94e77a6 feat: Suggestions support for prefer-regex-literals (#15077) (Yash Singh)
eafaf52 feat: add prefer-object-has-own rule (#15346) (Nitin Kumar)

Bug Fixes

7d832d4 fix: improve prefer-template fixer (#15230) (Nitin Kumar)
981fb48 fix: do not report global references in id-match rule (#15420) (Nitin Kumar)
f13d4a6 fix: improve autofix of prefer-object-has-own (#15419) (Nitin Kumar)
f4559a0 fix: add helpful message when test case has non-string code/name (#15425) (Bryan Mishkin)

Documentation

314c84c docs: add an incorrect code example in for-direction (#15434) (Holger Jeromin)
3928175 docs: add destructuring examples for computed-property-spacing (#15423) (Nitin Kumar)
a53e59e docs: add more examples for array-element-newline rule (#15427) (Nitin Kumar)
74cf0a0 docs: update CLA info (#15370) (Nitin Kumar)
e84195e docs: fix heading level for an option in class-methods-use-this rule (#15399) (Takuya Fukuju)

Chores

225f211 test: add destructuring test cases for computed-property-spacing (#15424) (Nitin Kumar)
f2c7ba6 ci: use node v16 for macOS and windows jobs (#15418) (Nitin Kumar)

ESLint v8.4.1 released

2021-12-06T00:00:00Z

Bug Fixes

234e3d9 fix: revert changes to reported locations in max-lines-per-function (#15397) (Milos Djermanovic)

Documentation

fa4d483 docs: fix typo in example for sort-keys rule (#15393) (Nitin Kumar)

ESLint v8.4.0 released

2021-12-03T00:00:00Z

Highlights

New Parser Option

The default parser has a new option allowReserved (boolean, default false). When set to true, reserved words can be used as identifiers.

This option can only be used with "ecmaVersion": 3.

{
    "parserOptions": {
        "ecmaVersion": 3,
        "allowReserved": true
    }
}

New Features for Custom Formatters

This release adds two new features for custom formatters.

Async Formatters

Formatters are now allowed to return Promise<string>. That is, a formatter can be an async function.

//------ my-formatter.js ------
module.exports = async function(results, context) {
    const something = await getSomethingAsync();
    // ...
    return formattedResults;
};

`context.cwd`

The context argument has a new property cwd (string, absolute path). It represents the working directory used for linting. This value comes from the cwd constructor option of the ESLint class, and formatters can use it to output relative paths more reliably than by using process.cwd().

//------ my-formatter.js ------
module.exports = function(results, context) {
    const cwd = context.cwd;
    // ...
};

Features

5771663 feat: add allowReserved parser option (#15387) (Milos Djermanovic)
32ac37a feat: Flat config support in Linter (refs #13481) (#15185) (Nicholas C. Zakas)
d041f34 feat: Treat Class/New Expressions as truthy in no-constant-condition (#15326) (Jordan Eldredge)
8f44cf5 feat: report only lines that exceed the limit in max-lines-per-function (#15140) (Sneh Khatri)
808ad35 feat: pass cwd to formatters (refs eslint/rfcs#57) (#13392) (Toru Nagashima)
f1b7499 feat: support async formatters (#15243) (MO)

Bug Fixes

4940cc5 fix: mark --rulesdir option as deprecated in CLI docs (#15310) (Kevin Partington)

Documentation

54deec5 docs: update integrations.md (#15380) (Vlad Sholokhov)
fa0423a docs: fix typo in PR template (#15365) (Nitin Kumar)
e233920 docs: enable a few more markdownlint rules and fix violations (#15368) (Bryan Mishkin)
632176d docs: Dedent needlessly indented example in getter-return docs (#15363) (Jordan Eldredge)
4497e88 docs: Update release notes blog post template (#15285) (Nicholas C. Zakas)

Chores

efede90 chore: upgrade @eslint/eslintrc@1.0.5 (#15389) (Milos Djermanovic)
0b8c846 chore: fix update-readme to avoid multiple consecutive blank lines (#15375) (Milos Djermanovic)
94b2a8b chore: Use default Chromium binary in M1 Mac tests (#15371) (Brandon Mills)
ba58d94 ci: use node v16 for Verify Files (#15364) (Nitin Kumar)
1e32ee5 chore: add jsdoc type annotation to rules (#15291) (Bryan Mishkin)

Contra becomes ESLint gold sponsor

2021-12-01T00:00:00Z

We are happy to share that Contra has become an ESLint gold sponsor, donating $1,000 each month for the ongoing maintenance and development of ESLint! Contra is a professional network built around independent work, allowing designers, developers, and more, to live and work the way they want.

Here’s what the folks at Contra had to say about ESLint:

“ESLint plays a major role in helping us create a safe and consistent experience across a growing number of codebases and engineers. We are grateful for all the open-source projects that are helping us build Contra, and ESLint is the first of many open-source projects that we are committed to back.” -– Gajus Kuizinas, Co-Founder / CTO at Contra

ESLint is grateful for the support of the Contra team, and we are putting these funds to work by paying more contributors to help maintain and develop ESLint. Donations such as these have allowed us to take on more ambitious projects, such as redesigning the ESLint website, with more to come in 2022.

ESLint v8.3.0 released

2021-11-21T00:00:00Z

Highlights

This release supports ES2022 class static blocks in rules, the default parser, and scope analysis.

class C {
    static x = ...;
    static y;
    static z;
    static {
        try {
            const obj = doSomethingWith(this.x);
            this.y = obj.y;
            this.z = obj.z;
        }
        catch {
            this.y = ...;
            this.z = ...;
        }
    }
}

It also supports #x in obj, officially known as ergonomic brand checks for private fields.

Features

60b0a29 feat: add allowProperties option to require-atomic-updates (#15238) (Milos Djermanovic)
79278a1 feat: update no-use-before-define for class static blocks (#15312) (Milos Djermanovic)
ddd01dc feat: update no-redeclare for class static blocks (#15313) (Milos Djermanovic)
de69cec feat: update no-inner-declarations for class static blocks (#15290) (Milos Djermanovic)
e2fe7ef feat: support for private-in syntax (fixes #14811) (#15060) (Yosuke Ota)
34bc8d7 feat: Update espree and eslint-scope (#15338) (Brandon Mills)
b171cd7 feat: update max-depth for class static blocks (#15316) (Milos Djermanovic)
6487df3 feat: update padded-blocks for class static blocks (#15333) (Milos Djermanovic)
194f36d feat: update the complexity rule for class static blocks (#15328) (Milos Djermanovic)
3530337 feat: update the indent rule for class static blocks (#15324) (Milos Djermanovic)
f03cd14 feat: update lines-around-comment for class static blocks (#15323) (Milos Djermanovic)
5c64747 feat: update brace-style for class static blocks (#15322) (Milos Djermanovic)
df2f1cc feat: update max-statements for class static blocks (#15315) (Milos Djermanovic)
fd5a0b8 feat: update prefer-const for class static blocks (#15325) (Milos Djermanovic)
b3669fd feat: code path analysis for class static blocks (#15282) (Milos Djermanovic)
15c1397 feat: update eslint-scope for class static blocks (#15321) (Milos Djermanovic)
1a1bb4b feat: update one-var for class static blocks (#15317) (Milos Djermanovic)
9b666e0 feat: update padding-line-between-statements for class static blocks (#15318) (Milos Djermanovic)
d3a267f feat: update class-methods-use-this for class static blocks (#15298) (Milos Djermanovic)
cdaa541 feat: update no-lone-blocks for class static blocks (#15295) (Milos Djermanovic)
8611538 feat: update block-spacing for class static blocks (#15297) (Milos Djermanovic)
7b56844 feat: update keyword-spacing for class static blocks (#15289) (Milos Djermanovic)
ea18711 feat: update no-extra-semi for class static blocks (#15287) (Milos Djermanovic)
0f0971f feat: update semi rule for class static blocks (#15286) (Milos Djermanovic)
abe740c feat: add examples for block-scoped-var with class static blocks (#15302) (Milos Djermanovic)
0338fd2 feat: Normalize ecmaVersion to eslint-scope when using custom parser (#15268) (Yosuke Ota)

Bug Fixes

8aa7645 fix: update vars-on-top for class static blocks (#15306) (Milos Djermanovic)
479a4cb fix: update semi-style for class static blocks (#15309) (Milos Djermanovic)
6d1c666 fix: update no-invalid-this and no-eval for class static blocks (#15300) (Milos Djermanovic)

Documentation

6b85426 docs: Expand --debug option description in the CLI documentation (#15308) (darkred)
3ae5258 docs: the strict rule does not apply to class static blocks (#15314) (Milos Djermanovic)
9309841 docs: Remove inconsistent colon in pull request docs (#15303) (Jordan Eldredge)
da238cc docs: remove deprecation note from lines-around-comment (#15293) (Milos Djermanovic)
1055f16 docs: no-unused-expressions - class static blocks don’t have directives (#15283) (Milos Djermanovic)
4c55216 docs: Add variables option to no-use-before-define (#15276) (Mathias Rasmussen)

Chores

edd8d24 chore: upgrade eslint-visitor-keys for class static blocks (#15277) (Milos Djermanovic)

The inception of ESLint

2021-11-09T00:00:00Z

If you’re like me, you probably use a lot of open source tools every day without thinking about how they got started. Few projects share the “why” of their creation: the actual problem they were trying to solve and when they first came across that problem. You can, of course, benefit from open source projects without understanding their origin story, but I always find it interesting to hear about how it all started.

I recently realized that I’d never shared the origin story of ESLint. I’ve shared some of the decisions I made along the way in previous posts but never the initial domino that fell and led to ESLint’s creation. As you will see, ESLint wasn’t created through some divine intervention or stroke of insight, but rather through a series of events that eventually built up to ESLint’s creation.

The bug

I was still fairly new at Box when a teammate was working on a strange bug. A client had reported problems using the web application in Internet Explorer 7 (we were probably one of the last companies supporting IE7 at that point). A developer had apparently used the native XMLHttpRequest object in some JavaScript code instead of our in-house wrapper. This wasn’t a problem for any other browser, and there wasn’t a problem testing with IE7 internally. The problem occurred because the client had an internal security policy that disabled ActiveX in Internet Explorer, and since the native XMLHttpRequest object in IE7 was really just a wrapper around the ActiveX object, it was blocked as well.

The solution was easy enough, just make sure everyone knows to use the in-house Ajax wrapper instead of the native XMLHttpRequest object. But how could we enforce this? It turned out that Box had a JavaScript “linter” as part of the build system. I put the word linter in quotes because it was really just a series of regular expressions that were run against JavaScript code. For this case, my teammate added a regular expression for “XMLHttpRequest” and that was the solution. The build would break going forward if someone tried to commit a JavaScript file matching that pattern.

In my experience, using regular expressions on source code was never a good idea. I wished that there was a better way to do checks like this one during the build. I figured that someone must have already solved this problem and so I started looking for solutions.

Could it be JSHint?

The first thing I did was email the maintainer of JSHint at that time, Anton Kovalyov[1]. I had remembered reading a blog post[2] that said JSHint was planning to support plugins but couldn’t find any information about that feature being implemented. From past experience contributing to JSHint and from modifying JSLint for a project at Yahoo, I knew JSHint hadn’t initially been setup to support plugins, and without formal support there wouldn’t be an easy way to modify JSHint to do what I wanted.

Anton informed me that the plugin proposal had stalled and didn’t look like it would be implemented. I was disappointed, as this seemed like the most direct path to solving the problem. I thanked him and asked him to please not be offended if I create a linter that did what I needed. I wanted to support JSHint, but I felt like this was a problem that needed to be solved with JSHint or without it.

The inspiration

After digging around in the build system at Box, I found there was actually a PHP linter running in addition to the makeshift JavaScript linter. The PHP linter, however, was a lot more involved that the JavaScript one. Instead of using regular expressions, the PHP linter parsed the code into an abstract syntax tree (AST) and then inspected the AST for the patterns to report.

I was probably shaking my head “yes” as I read through that code. Immediately I realized that this was exactly what I needed to do for JavaScript. If only there was some way to parse JavaScript into an AST and then inspect the AST for problems.

The groundwork

With all of this floating around in my brain, I invited Ariya Hidayat[3] to give a talk at Box about whatever topic he pleased. It just so happened that he gave a talk on Esprima[4], the JavaScript parser he wrote in JavaScript. During that talk, Ariya discussed why having an AST representation of JavaScript was useful and referenced several already-existing tools built on top of Esprima. Among those tools were estraverse for traversing the AST and escope for scope analysis, both written by Yusuke Suzuki.

As Ariya continued talking and giving examples of the types of problems an AST can solve, the idea for a new tool formed in my head. It made sense to me that there should be one tool that could perform all of the evaluations Ariya mentioned. After all, they are all just using the AST for different purposes. Why not have one AST they all can use?

The beginning

Thanks largely to the availability of Esprima, estraverse, and escope, I was able to put together the first prototype of ESLint over a couple of weekends. To me, these three utilities represented everything that I needed to create a new tool that could easily find problem patterns in JavaScript code. If I had to create those from scratch, I have no doubt that ESLint would not exist today. Building on top of those tools, I was able to iterate quickly, and eventually, the tool you know today as ESLint was born.

(I feel it’s important to point out that I was not the only one looking to create an AST-based linter at the time. JSCS[5] was also under development at around the same time, and current ESLint maintainer Ilya Volodin was working on his own project before discovering ESLint. If I had not come up with something like ESLint then someone else undoubtedly would have. All of the pieces were already out there thanks to Ariya and Yusuke, someone just had to put them together in a useful way.)

References

Anton Kovalyov (antonkovalyov.com)
JSHint 3 Plans (jshint.com)
Ariya Hidayat (ariya.io)
JavaScript Code Analysis (speakerdeck.com)
JSCS (jscs.info)

ESLint v8.2.0 released

2021-11-05T00:00:00Z

Features

c9fefd2 feat: report class evaluation TDZ errors in no-use-before-define (#15134) (Milos Djermanovic)

Documentation

c415c04 docs: Use string rule severity in CLI examples (#15253) (Kevin Partington)
12b627d docs: fix typo in working-with-rules.md (#15233) (Nitin Kumar)
a86ffc0 docs: fix broken anchor in configuration files (#15223) (Pierre Berger)
ee8af5f docs: Link to unit tests from rule documentation (#15207) (Brandon Mills)
1c0ca3c docs: add ci and perf tags for commit (#15215) (Nitin Kumar)

796587a build: upgrade eslint-release to v3.2.0 to support conventional commits (#15246) (Milos Djermanovic)

Chores

cf5b6be chore: update @eslint/eslintrc to avoid different versions of js-yaml (#15265) (Milos Djermanovic)
4fd7a6c perf: don’t prepare a fix for valid code in key-spacing (#15239) (Milos Djermanovic)
fda533c chore: update strip-ansi dependency (#15221) (Nitin Kumar)
67949bd ci: Remove Node 16 CI prerelease workaround (#14935) (Brandon Mills)

ESLint v8.1.0 released

2021-10-22T00:00:00Z

Highlights

One new rule has been added: no-unused-private-class-members. This rule reports unused class private fields, methods and accessors.
RuleTester now allows name property in test case objects. If you specify name, it will be output instead of the code.

Features

3d370fb New: Add no-unused-private-class-members rule (fixes #14859) (#14895) (Tim van der Lippe)
e926b17 New: Add name to RuleTester (#15179) (Gareth Jones)

Bug Fixes

d9d84a0 Fix: keyword-spacing conflict with space-infix-ops on > (fixes #14712) (#15172) (Milos Djermanovic)
a1f7ad7 Fix: allow baseConfig to extend preloaded plugin config (fixes #15079) (#15187) (Milos Djermanovic)

Documentation

446b4b3 Docs: Update commit message format docs (#15200) (Nicholas C. Zakas)
0fb3bb2 Docs: remove instanceof from keyword-spacing docs (#15180) (Milos Djermanovic)
35f3254 Docs: Describe range in rule docs (fixes #14162) (#15174) (Nicholas C. Zakas)
2b32f50 Docs: Fix typo in README.md (#15168) (Dmitriy Fishman)
2cfbd4b Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

249a040 Upgrade: eslint-plugin-eslint-plugin to v4 (#15169) (Bryan Mishkin)

1b87fa8 Build: add node v17 (#15193) (唯然)

Chores

90a5b6b Chore: improve performance of :function selector (#15181) (Milos Djermanovic)
31af1c8 Chore: fix counting of files in performance test (#15190) (Milos Djermanovic)
b5049c8 Chore: Update stale bot settings (#15173) (Nicholas C. Zakas)
dd58cd4 Chore: migrate master to main (#15062) (Nitesh Seram)
ec0f8e0 Chore: Add stale issue/PR checker (#15151) (Nicholas C. Zakas)

ESLint v8.0.1 released

2021-10-13T00:00:00Z

This release contains a workaround that will allow Jest to work with ESLint v8.

Documentation

ff5fcd4 Docs: add 13 as allowed ecma version (fixes #15159) (#15162) (唯然)

Dependency Upgrades

f9217e5 Upgrade: @eslint/eslintrc@1.0.3 for Jest workaround (#15164) (Brandon Mills)

Chores

c584a63 Chore: add ecmaVersion 13 to types.js (#15163) (Milos Djermanovic)

ESLint v8.0.0 released

2021-10-09T00:00:00Z

Highlights

There are several breaking changes in v8.0.0. We’ve created a migration guide to explain the breaking changes and describe how to upgrade. In addition, there are several new features:

ESLint’s default parser and all core rules now fully support the following ES2022 syntax:
- Class public instance fields and private instance fields
- Class public static fields and private static fields
- Class private instance methods and accessors
- Class private static methods and accessors
- RegExp match indices
- Top-level await
Autofix can now remove unused disable directives when --fix and --report-unused-disable-directives are used together.
The use of reserved words as identifiers in ES3 is now disallowed. This change only affects users with default parser configured with { "ecmaVersion": 3 } in parser options.
The class-methods-use-this rule has a new enforceForClassFields option.
The max-classes-per-file rule has a new ignoreExpressions option.
The meta.docs.category property has been removed from all core rules.

Breaking Changes

7cf96cf Breaking: Disallow reserved words in ES3 (fixes #15017) (#15046) (Milos Djermanovic)
305e14a Breaking: remove meta.docs.category in core rules (fixes #13398) (#14594) (薛定谔的猫)
24c9f2a Breaking: Strict package exports (refs #13654) (#14706) (Nicholas C. Zakas)
86d31a4 Breaking: disallow SourceCode#getComments() in RuleTester (refs #14744) (#14769) (Milos Djermanovic)
1d2213d Breaking: Fixable disable directives (fixes #11815) (#14617) (Josh Goldberg)
4a7aab7 Breaking: require meta for fixable rules (fixes #13349) (#14634) (Milos Djermanovic)
d6a761f Breaking: Require meta.hasSuggestions for rules with suggestions (#14573) (Bryan Mishkin)
6bd747b Breaking: support new regex d flag (fixes #14640) (#14653) (Yosuke Ota)
8b4f3ab Breaking: fix comma-dangle schema (fixes #13739) (#14030) (Joakim Nilsson)
b953a4e Breaking: upgrade espree and support new class features (refs #14343) (#14591) (Toru Nagashima)
8cce06c Breaking: add some rules to eslint:recommended (refs #14673) (#14691) (薛定谔的猫)
86bb63b Breaking: Drop codeframe and table formatters (#14316) (Federico Brigante)
f3cb320 Breaking: drop node v10/v13/v15 (fixes #14023) (#14592) (薛定谔的猫)

Enhancements

67c0074 Update: Suggest missing rule in flat config (fixes #14027) (#15074) (Nicholas C. Zakas)
cf34e5c Update: space-before-blocks ignore after switch colons (fixes #15082) (#15093) (Milos Djermanovic)
14a4739 Update: no-new-func rule catching eval case of MemberExpression (#14860) (Mojtaba Samimi)
0a1a850 Update: include ruleId in error logs (fixes #15037) (#15053) (Ari Perkkiö)
88a3952 Update: support class fields in the complexity rule (refs #14857) (#14957) (Milos Djermanovic)
6d1ccb6 Update: enforceForClassFields in class-methods-use-this (refs #14857) (#15018) (YeonJuan)
dd10937 Update: added ignoreExpressions option to max-classes-per-file (#15000) (Josh Goldberg)
05ca24c Update: Code path analysis for class fields (fixes #14343) (#14886) (Nicholas C. Zakas)
44c6fc8 Update: support class fields in func-name-matching (refs #14857) (#14964) (Milos Djermanovic)
3d7d5fb Update: reporting loc for never option in eol-last (refs #12334) (#14840) (Nitin Kumar)
f110926 Update: fix no-unused-vars false negative with comma operator (#14928) (Sachin)
26b0cd9 Update: fix no-unreachable logic for class fields (refs #14857) (#14920) (Milos Djermanovic)
9052eee Update: check class fields in no-extra-parens (refs #14857) (#14906) (Milos Djermanovic)

Bug Fixes

2174a6f Fix: require-atomic-updates property assignment message (fixes #15076) (#15109) (Milos Djermanovic)
c9efb5f Fix: preserve formatting when rules are removed from disable directives (#15081) (Milos Djermanovic)
9bd3d87 Fix: semicolon-less style in lines-between-class-members (refs #14857) (#15045) (Milos Djermanovic)
f966fe6 Fix: Update semi for class-fields (refs #14857) (#14945) (Nicholas C. Zakas)
e9764f3 Fix: no-undef-init should not apply to class fields (refs #14857) (#14994) (Milos Djermanovic)
3409785 Fix: camelcase ignoreGlobals shouldn’t apply to undef vars (refs #14857) (#14966) (Milos Djermanovic)
ee1b54f Fix: keyword-spacing private name compat (refs #14857) (#14946) (Nicholas C. Zakas)
af96584 Fix: handle computed class fields in operator-linebreak (refs #14857) (#14915) (Milos Djermanovic)
a773b99 Fix: no-useless-computed-key edge cases with class fields (refs #14857) (#14903) (Milos Djermanovic)
cbc43da Fix: prefer-destructuring PrivateIdentifier false positive (refs #14857) (#14897) (Milos Djermanovic)
ccb9a91 Fix: dot-notation false positive with private identifier (refs #14857) (#14898) (Milos Djermanovic)

Documentation

f885fe0 Docs: add note and example for extending the range of fix (refs #13706) (#13748) (Milos Djermanovic)
3da1509 Docs: Add jsdoc type annotation to sample rule (#15085) (Bryan Mishkin)
68a49a9 Docs: Update Rollup Integrations (#15142) (xiaohai)
d867f81 Docs: Remove a dot from curly link (#15128) (Mauro Murru)
2d654f1 Docs: add example .eslintrc.json (#15087) (Nicolas Mattia)
16034f0 Docs: fix fixable example (#15107) (QiChang Li)
7f2346b Docs: Update release blog post template (#15094) (Nicholas C. Zakas)
a744dfa Docs: Update CLA info (#15058) (Brian Warner)
91e82f5 Docs: LintMessage.line and column are possibly undefined (#15032) (Brandon Mills)
dd56631 Docs: remove duplicate code path analysis document (#15033) (Milos Djermanovic)
8c61f5a Docs: add info about non-capturing groups to prefer-named-capture-group (#15009) (Andrzej Wódkiewicz)
4338b74 Docs: add no-dupe-class-members examples with class fields (refs #14857) (#15005) (Milos Djermanovic)
88b4e3d Docs: Make clear how rule options are overridden (fixes #14962) (#14976) (Jake Ob)
4165c7f Docs: Clarify Linter vs ESLint in node.js api docs (fixes #14953) (#14995) (Brian Bartels)
80cfb8f Docs: fix typo in migration guide (#14985) (Nitin Kumar)
396a0e3 Docs: update ScopeManager with class fields (#14974) (Milos Djermanovic)
6663e7a Docs: remove docs script (fixes #14288) (#14971) (Nitin Kumar)
44f7de5 Docs: Update deprecated information (#14961) (TagawaHirotaka)
a8bcef7 Docs: Add 2021 and 2022 to supported ECMAScript versions (#14952) (coderaiser)
b301069 Docs: fix ‘When Not To Use’ in prefer-named-capture-group (refs #14959) (#14969) (Milos Djermanovic)
e98f14d Docs: Fix typo in no-implicit-globals.md (#14954) (jwbth)
81c60f4 Docs: document ESLint api (#14934) (Sam Chen)
28fe19c Docs: Add v8.0.0 migration guide (fixes #14856) (#14884) (Nicholas C. Zakas)
1f5d088 Docs: add an example Object.assign() for rule no-import-assign (#14916) (薛定谔的猫)
c4e5802 Docs: improve rule details for no-console (fixes #14793) (#14901) (Nitin Kumar)
5c3a470 Docs: add class fields in no-multi-assign documentation (refs #14857) (#14907) (Milos Djermanovic)
d234d89 Docs: add class fields in func-names documentation (refs #14857) (#14908) (Milos Djermanovic)
e037d61 Docs: Mention workaround for escaping the slash character in selectors (#14675) (Aria)
81f03b6 Docs: Update license copyright (#14877) (Nicholas C. Zakas)

Dependency Upgrades

7d3f7f0 Upgrade: unfrozen @eslint/eslintrc (fixes #15036) (#15146) (Brandon Mills)
9e5c2e8 Upgrade: @eslint/eslintrc@1.0.1 (#15047) (Milos Djermanovic)
ec9db63 Upgrade: @eslint/eslintrc@1.0.0 (#14865) (Milos Djermanovic)
62c6fe7 Upgrade: Debug 4.0.1 > 4.3.2 (#14892) (sandesh bafna)
88db3f5 Upgrade: js-yaml to v4 (#14890) (Bryan Mishkin)
ae6072b Upgrade: eslint-visitor-keys to v3 (#14902) (Bryan Mishkin)
e53d8cf Upgrade: markdownlint dev dependencies (#14883) (Bryan Mishkin)
d66e941 Upgrade: @humanwhocodes/config-array to 0.6 (#14891) (Bryan Mishkin)

71faa38 Build: changelog update for 8.0.0-rc.0 (ESLint Jenkins)
d148ffd Build: changelog update for 8.0.0-beta.2 (ESLint Jenkins)
95cc61e Build: changelog update for 8.0.0-beta.1 (ESLint Jenkins)
c74fe08 Build: Force prerelease peer dep for Node 16 in CI (#14933) (Brandon Mills)
027165c Build: changelog update for 8.0.0-beta.0 (ESLint Jenkins)
b8b2d55 Build: add codeql (#14729) (薛定谔的猫)

Chores

fabdf8a Chore: Remove target.all from Makefile.js (#15088) (Hirotaka Tagawa / wafuwafu13)
05d7140 Chore: document target global in Makefile.js (#15084) (Hirotaka Tagawa / wafuwafu13)
47be800 Chore: test Property > .key with { a = 1 } pattern (fixes #14799) (#15072) (Milos Djermanovic)
9fb0f70 Chore: fix bug report template (#15061) (Milos Djermanovic)
f87e199 Chore: Cleanup issue templates (#15039) (Nicholas C. Zakas)
921ba1e Chore: fix failing cli test (#15041) (Milos Djermanovic)
143a598 Chore: Switch issues to use forms (#15024) (Nicholas C. Zakas)
b4232d4 Chore: Add test that deprecated rules display a deprecated notice (#14989) (TagawaHirotaka)
db15183 Chore: Refactor comments of tests (#14956) (TagawaHirotaka)
a79c9f3 Chore: Enforce jsdoc check-line-alignment never (#14955) (Brett Zamir)
2d18db6 Chore: add test for merging parserOptions in Linter (#14948) (Milos Djermanovic)
9a4ae3b Chore: Apply comment require-description and check ClassDeclaration (#14949) (Brett Zamir)
8344675 Chore: fix small typo (#14951) (Sosuke Suzuki)
58840ac Chore: Update jsdoc plugin and tweak rules in effect (#14814) (Brett Zamir)
be334f9 Chore: Fix Makefile call to linter.getRules() (#14932) (Brandon Mills)
0c86b68 Chore: Replace old syntax for Array flat/flatMap (#14614) (Stephen Wade)
6a89f3f Chore: ignore yarn-error.log and .pnpm-debug.log (#14925) (Nitin Kumar)
3b6cd89 Chore: Add rel/abs path tests in no-restricted-{imports/modules} rules (#14910) (Bryan Mishkin)
f984515 Chore: add assertions on reporting location in semi (#14899) (Nitin Kumar)
149230c Chore: Specify Node 14.x for Verify Files CI job (#14896) (Milos Djermanovic)
537cf6a Chore: update glob-parent (fixes #14879)(#14887) (Nitin Kumar)
f7b4a3f Chore: update dev deps to latest (#14624) (薛定谔的猫)

ESLint v8.0.0-rc.0 released

2021-09-24T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

This version of ESLint is provided to gather feedback from the community before releasing the final version. Please try it and report any unexpected issues.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@8.0.0-rc.0 --save-dev

Migration Guide

Enhancements

67c0074 Update: Suggest missing rule in flat config (fixes #14027) (#15074) (Nicholas C. Zakas)
cf34e5c Update: space-before-blocks ignore after switch colons (fixes #15082) (#15093) (Milos Djermanovic)
14a4739 Update: no-new-func rule catching eval case of MemberExpression (#14860) (Mojtaba Samimi)
0a1a850 Update: include ruleId in error logs (fixes #15037) (#15053) (Ari Perkkiö)

Bug Fixes

c9efb5f Fix: preserve formatting when rules are removed from disable directives (#15081) (Milos Djermanovic)

Documentation

7f2346b Docs: Update release blog post template (#15094) (Nicholas C. Zakas)
a744dfa Docs: Update CLA info (#15058) (Brian Warner)

Chores

fabdf8a Chore: Remove target.all from Makefile.js (#15088) (Hirotaka Tagawa / wafuwafu13)
05d7140 Chore: document target global in Makefile.js (#15084) (Hirotaka Tagawa / wafuwafu13)
47be800 Chore: test Property > .key with { a = 1 } pattern (fixes #14799) (#15072) (Milos Djermanovic)
9fb0f70 Chore: fix bug report template (#15061) (Milos Djermanovic)
f87e199 Chore: Cleanup issue templates (#15039) (Nicholas C. Zakas)

ESLint v8.0.0-beta.2 released

2021-09-10T00:00:00Z

Highlights

The use of reserved words as identifiers in ES3 is now disallowed. This change only affects users with default parser configured with { "ecmaVersion": 3 } in parser options.
All core rules have been updated to support ES2022 class fields and private class members. ESLint now fully supports the following ES2022 syntax:
- Class public instance fields and private instance fields
- Class public static fields and private static fields
- Class private instance methods and accessors
- Class private static methods and accessors
- RegExp match indices
- Top-level await
The class-methods-use-this rule has a new enforceForClassFields option.
The max-classes-per-file rule has a new ignoreExpressions option.

Since this is a beta release, it is not expected to be ready for production, but please try it and report any unexpected issues.

Notes

VS Code ESLint extension has added support for ESLint v8.0.0, you’ll just need to install the latest v2.1.25 of the extension.
We have received reports from plugin authors about problems with testing plugin rules with Jest, as Jest’s resolver currently doesn’t support subpath exports. For a workaround, please see this comment.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@8.0.0-beta.2 --save-dev

Migration Guide

Breaking Changes

7cf96cf Breaking: Disallow reserved words in ES3 (fixes #15017) (#15046) (Milos Djermanovic)

Enhancements

88a3952 Update: support class fields in the complexity rule (refs #14857) (#14957) (Milos Djermanovic)
6d1ccb6 Update: enforceForClassFields in class-methods-use-this (refs #14857) (#15018) (YeonJuan)
dd10937 Update: added ignoreExpressions option to max-classes-per-file (#15000) (Josh Goldberg)

Bug Fixes

9bd3d87 Fix: semicolon-less style in lines-between-class-members (refs #14857) (#15045) (Milos Djermanovic)
f966fe6 Fix: Update semi for class-fields (refs #14857) (#14945) (Nicholas C. Zakas)
e9764f3 Fix: no-undef-init should not apply to class fields (refs #14857) (#14994) (Milos Djermanovic)

Documentation

91e82f5 Docs: LintMessage.line and column are possibly undefined (#15032) (Brandon Mills)
dd56631 Docs: remove duplicate code path analysis document (#15033) (Milos Djermanovic)
8c61f5a Docs: add info about non-capturing groups to prefer-named-capture-group (#15009) (Andrzej Wódkiewicz)
4338b74 Docs: add no-dupe-class-members examples with class fields (refs #14857) (#15005) (Milos Djermanovic)
88b4e3d Docs: Make clear how rule options are overridden (fixes #14962) (#14976) (Jake Ob)
4165c7f Docs: Clarify Linter vs ESLint in node.js api docs (fixes #14953) (#14995) (Brian Bartels)
80cfb8f Docs: fix typo in migration guide (#14985) (Nitin Kumar)

Dependency Upgrades

9e5c2e8 Upgrade: @eslint/eslintrc@1.0.1 (#15047) (Milos Djermanovic)

Chores

921ba1e Chore: fix failing cli test (#15041) (Milos Djermanovic)
143a598 Chore: Switch issues to use forms (#15024) (Nicholas C. Zakas)
b4232d4 Chore: Add test that deprecated rules display a deprecated notice (#14989) (TagawaHirotaka)

ESLint v8.0.0-beta.1 released

2021-08-27T00:00:00Z

Highlights

Beta testing revealed that the impact of the breaking change to allow line comment directives for all directives that previously required block comments outweighs the benefits of this feature due to a high number of accidental directives, so we decided to revert this change and exclude this feature from v8.0.0.
Code Path Analysis now supports ES2022 class fields. In particular, each class field initializer now starts a separate code path. A new origin property has been added to CodePath objects.
The meta.docs.category property has been removed from all core rules.

Since this is a beta release, it is not expected to be ready for production, but please try it and report any unexpected issues.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@8.0.0-beta.1 --save-dev

Migration Guide

Breaking Changes

305e14a Breaking: remove meta.docs.category in core rules (fixes #13398) (#14594) (薛定谔的猫)

Enhancements

05ca24c Update: Code path analysis for class fields (fixes #14343) (#14886) (Nicholas C. Zakas)
44c6fc8 Update: support class fields in func-name-matching (refs #14857) (#14964) (Milos Djermanovic)
3d7d5fb Update: reporting loc for never option in eol-last (refs #12334) (#14840) (Nitin Kumar)
f110926 Update: fix no-unused-vars false negative with comma operator (#14928) (Sachin)
26b0cd9 Update: fix no-unreachable logic for class fields (refs #14857) (#14920) (Milos Djermanovic)

Bug Fixes

3409785 Fix: camelcase ignoreGlobals shouldn’t apply to undef vars (refs #14857) (#14966) (Milos Djermanovic)
ee1b54f Fix: keyword-spacing private name compat (refs #14857) (#14946) (Nicholas C. Zakas)

Documentation

396a0e3 Docs: update ScopeManager with class fields (#14974) (Milos Djermanovic)
6663e7a Docs: remove docs script (fixes #14288) (#14971) (Nitin Kumar)
44f7de5 Docs: Update deprecated information (#14961) (TagawaHirotaka)
a8bcef7 Docs: Add 2021 and 2022 to supported ECMAScript versions (#14952) (coderaiser)
b301069 Docs: fix ‘When Not To Use’ in prefer-named-capture-group (refs #14959) (#14969) (Milos Djermanovic)
e98f14d Docs: Fix typo in no-implicit-globals.md (#14954) (jwbth)
81c60f4 Docs: document ESLint api (#14934) (Sam Chen)

c74fe08 Build: Force prerelease peer dep for Node 16 in CI (#14933) (Brandon Mills)

Chores

db15183 Chore: Refactor comments of tests (#14956) (TagawaHirotaka)
a79c9f3 Chore: Enforce jsdoc check-line-alignment never (#14955) (Brett Zamir)
2d18db6 Chore: add test for merging parserOptions in Linter (#14948) (Milos Djermanovic)
9a4ae3b Chore: Apply comment require-description and check ClassDeclaration (#14949) (Brett Zamir)
8344675 Chore: fix small typo (#14951) (Sosuke Suzuki)
58840ac Chore: Update jsdoc plugin and tweak rules in effect (#14814) (Brett Zamir)

ESLint v8.0.0-beta.0 released

2021-08-14T00:00:00Z

Highlights

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide. In addition, there are some new features:

The default parser now supports ES2022 syntax, including class fields and top-level await. Some rules still need to be updated, and you can follow progress on the tracking issue.
Autofix gained support for removing unused disable directives when using --fix with --report-unused-disable-directives.

Since this is a beta release, it is not expected to be ready for production, but please try it and report any unexpected issues.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@8.0.0-beta.0 --save-dev

Migration Guide

Breaking Changes

24c9f2a Breaking: Strict package exports (refs #13654) (#14706) (Nicholas C. Zakas)
86d31a4 Breaking: disallow SourceCode#getComments() in RuleTester (refs #14744) (#14769) (Milos Djermanovic)
1d2213d Breaking: Fixable disable directives (fixes #11815) (#14617) (Josh Goldberg)
4a7aab7 Breaking: require meta for fixable rules (fixes #13349) (#14634) (Milos Djermanovic)
d6a761f Breaking: Require meta.hasSuggestions for rules with suggestions (#14573) (Bryan Mishkin)
4c841b8 Breaking: allow all directives in line comments (fixes #14575) (#14656) (薛定谔的猫)
6bd747b Breaking: support new regex d flag (fixes #14640) (#14653) (Yosuke Ota)
8b4f3ab Breaking: fix comma-dangle schema (fixes #13739) (#14030) (Joakim Nilsson)
b953a4e Breaking: upgrade espree and support new class features (refs #14343) (#14591) (Toru Nagashima)
8cce06c Breaking: add some rules to eslint:recommended (refs #14673) (#14691) (薛定谔的猫)
86bb63b Breaking: Drop codeframe and table formatters (#14316) (Federico Brigante)
f3cb320 Breaking: drop node v10/v13/v15 (fixes #14023) (#14592) (薛定谔的猫)

Enhancements

9052eee Update: check class fields in no-extra-parens (refs #14857) (#14906) (Milos Djermanovic)

Bug Fixes

af96584 Fix: handle computed class fields in operator-linebreak (refs #14857) (#14915) (Milos Djermanovic)
a773b99 Fix: no-useless-computed-key edge cases with class fields (refs #14857) (#14903) (Milos Djermanovic)
cbc43da Fix: prefer-destructuring PrivateIdentifier false positive (refs #14857) (#14897) (Milos Djermanovic)
ccb9a91 Fix: dot-notation false positive with private identifier (refs #14857) (#14898) (Milos Djermanovic)

Documentation

28fe19c Docs: Add v8.0.0 migration guide (fixes #14856) (#14884) (Nicholas C. Zakas)
1f5d088 Docs: add an example Object.assign() for rule no-import-assign (#14916) (薛定谔的猫)
c4e5802 Docs: improve rule details for no-console (fixes #14793) (#14901) (Nitin Kumar)
5c3a470 Docs: add class fields in no-multi-assign documentation (refs #14857) (#14907) (Milos Djermanovic)
d234d89 Docs: add class fields in func-names documentation (refs #14857) (#14908) (Milos Djermanovic)
e037d61 Docs: Mention workaround for escaping the slash character in selectors (#14675) (Aria)
81f03b6 Docs: Update license copyright (#14877) (Nicholas C. Zakas)

Dependency Upgrades

ec9db63 Upgrade: @eslint/eslintrc@1.0.0 (#14865) (Milos Djermanovic)
62c6fe7 Upgrade: Debug 4.0.1 > 4.3.2 (#14892) (sandesh bafna)
88db3f5 Upgrade: js-yaml to v4 (#14890) (Bryan Mishkin)
ae6072b Upgrade: eslint-visitor-keys to v3 (#14902) (Bryan Mishkin)
e53d8cf Upgrade: markdownlint dev dependencies (#14883) (Bryan Mishkin)
d66e941 Upgrade: @humanwhocodes/config-array to 0.6 (#14891) (Bryan Mishkin)

b8b2d55 Build: add codeql (#14729) (薛定谔的猫)

Chores

be334f9 Chore: Fix Makefile call to linter.getRules() (#14932) (Brandon Mills)
0c86b68 Chore: Replace old syntax for Array flat/flatMap (#14614) (Stephen Wade)
6a89f3f Chore: ignore yarn-error.log and .pnpm-debug.log (#14925) (Nitin Kumar)
3b6cd89 Chore: Add rel/abs path tests in no-restricted-{imports/modules} rules (#14910) (Bryan Mishkin)
f984515 Chore: add assertions on reporting location in semi (#14899) (Nitin Kumar)
149230c Chore: Specify Node 14.x for Verify Files CI job (#14896) (Milos Djermanovic)
537cf6a Chore: update glob-parent (fixes #14879)(#14887) (Nitin Kumar)
f7b4a3f Chore: update dev deps to latest (#14624) (薛定谔的猫)

ESLint v7.32.0 released

2021-07-30T00:00:00Z

Highlights

The new --exit-on-fatal-error option will treat parsing errors as fatal and return exit code 2. By default, parsing errors return exit code 1 like rule violations.

Features

1bfbefd New: Exit on fatal error (fixes #13711) (#14730) (Antonios Katopodis)

Enhancements

faecf56 Update: change reporting location for curly rule (refs #12334) (#14766) (Nitin Kumar)

Bug Fixes

d7dc07a Fix: ignore lines with empty elements (fixes #12756) (#14837) (Soufiane Boutahlil)

Documentation

d53d906 Docs: Prepare data for website to indicate rules with suggestions (#14830) (Bryan Mishkin)
d28f2ff Docs: Reference eslint-config-eslint to avoid potential for staleness (#14805) (Brett Zamir)
f9c164f Docs: New syntax issue template (#14826) (Nicholas C. Zakas)
ed945bd Docs: fix multiple broken links (#14833) (Sam Chen)
6641d88 Docs: Update README team and sponsors (ESLint Jenkins)

Chores

3c78a7b Chore: Adopt eslint-plugin/prefer-message-ids rule internally (#14841) (Bryan Mishkin)
ed007c8 Chore: Simplify internal no-invalid-meta rule (#14842) (Bryan Mishkin)
8be8a36 Chore: Adopt eslint-plugin/require-meta-docs-url rule internally (#14823) (Bryan Mishkin)
eba0c45 Chore: assertions on reporting loc in unicode-bom (refs #12334) (#14809) (Nitin Kumar)
60df44c Chore: use actions/setup-node@v2 (#14816) (Nitin Kumar)

ESLint v7.31.0 released

2021-07-17T00:00:00Z

Enhancements

a96b05f Update: add end location to report in consistent-return (refs #12334) (#14798) (Nitin Kumar)
ddffa8a Update: Indicating the operator in question (#14764) (Paul Smith)
bba714c Update: Clarifying what changes need to be made in no-mixed-operators (#14765) (Paul Smith)

Documentation

e0e8e30 Docs: update BUG_REPORT template (#14787) (Nitin Kumar)
39115c8 Docs: provide more context to no-eq-null (#14801) (gfyoung)
9a3c73c Docs: fix a broken link (#14790) (Sam Chen)
b0d22e3 Docs: Mention benefit of providing meta.docs.url (#14774) (Bryan Mishkin)

Dependency Upgrades

efdbb12 Upgrade: @eslint/eslintrc to v0.4.3 (#14808) (Brandon Mills)

Chores

a6a7438 Chore: pin fs-teardown@0.1.1 (#14771) (Milos Djermanovic)

ESLint v7.30.0 released

2021-07-02T00:00:00Z

Highlights

You can now set "ecmaVersion" to "latest" under parserOptions in your configuration file:

{
    "parserOptions": {
        "ecmaVersion": "latest"
    }
}

"ecmaVersion": "latest" always enables the latest supported ECMAScript version in ESLint’s default parser.

Please note that this feature applies only if you are using the default parser. If you’re using a custom parser, refer to the parser’s documentation for the list of available options.

Enhancements

ed1da5d Update: ecmaVersion allows “latest” (#14720) (薛定谔的猫)
104c0b5 Update: improve use-isnan rule to detect Number.NaN (fixes #14715) (#14718) (Nitin Kumar)
b08170b Update: Implement FlatConfigArray (refs #13481) (#14321) (Nicholas C. Zakas)

Documentation

19a871a Docs: Suggest linting plugins for ESLint plugin developers (#14754) (Bryan Mishkin)
aa87329 Docs: fix broken links (#14756) (Sam Chen)
278813a Docs: fix and add more examples for new-cap rule (fixes #12874) (#14725) (Nitin Kumar)
1b8997a Docs: Fix getRulesMetaForResults link syntax (#14723) (Brandon Mills)
aada733 Docs: fix two broken links (#14726) (Sam Chen)
8972529 Docs: Update README team and sponsors (ESLint Jenkins)

Chores

5f74642 Chore: don’t check Program.start in SourceCode#getComments (refs #14744) (#14748) (Milos Djermanovic)
f113cdd Chore: upgrade eslint-plugin-eslint-plugin (#14738) (薛定谔的猫)

ESLint v7.29.0 released

2021-06-18T00:00:00Z

Highlights

The ESLint class has a new getRulesMetaForResults() method that returns meta information for rules in lint results. ESLint integrations should migrate to ESLint#getRulesMetaForResults() from the getRules() method on the deprecated CLIEngine class.

RuleTester test cases now support an optional only boolean property that allows running a single test case in isolation for easier debugging.

Features

bfbfe5c New: Add only to RuleTester (refs eslint/rfcs#73) (#14677) (Brandon Mills)
c2cd7b4 New: Add ESLint#getRulesMetaForResults() (refs #13654) (#14716) (Nicholas C. Zakas)

Bug Fixes

6a1c7a0 Fix: allow fallthrough comment inside block (fixes #14701) (#14702) (Kevin Gibbons)

Documentation

a47e5e3 Docs: Add Mega-Linter to the list of integrations (#14707) (Nicolas Vuillamy)
c93a222 Docs: fix a broken link (#14697) (Sam Chen)

Chores

eea7e0d Chore: remove duplicate code (#14719) (Nitin Kumar)
353ddf9 Chore: enable reportUnusedDisableDirectives in eslint-config-eslint (#14699) (薛定谔的猫)
757c495 Chore: add some rules to eslint-config-eslint (#14692) (薛定谔的猫)

What's coming in ESLint v8.0.0

2021-06-08T00:00:00Z

Last week, the Technical Steering Committee (TSC) met to finalize the features for ESLint v8.0.0. This feature set had not yet been locked down even as v8.0.0 work began and so this represented an important milestone that allows us to focus on getting this next major release shipped. You can see everything that is planned for v8.0.0 on our project board.

Significant changes in v8.0.0

The following changes are important to understand as we move towards v8.0.0.

Dropping support for Node.js v10.x, 13.x, and 15.x

Node.js v10.x end-of-life was April 30, 2021, Node.js v13.x end-of-life was June 1, 2020, and Node.js v15.x end-of-life is this month (June 2021). As a result, ESLint v8.0.0 removes support for all three of these Node.js versions.

Removing the `codeframe` and `table` formatters

In an ongoing effort to reduce the install size of ESLint, we have decided to remove the codeframe and table formatters from the core of ESLint. Both of these formatters include dependencies that aren’t used anywhere else in ESLint. If you are using these formatters currently, you’ll need to install the standalone packages (eslint-formatter-codeframe and eslint-formatter-table) for use with ESLint v8.0.0.

Support for ES2022 class fields, top-level `await`, and regexp matching indices

Support for ES2022 comes to ESLint v8.0.0 with native support for class fields, top-level await, and regexp matching indices.

Rules with suggestions now require the `meta.hasSuggestions` property

Beginning in ESLint v8.0.0, rules that provide suggestions must include a meta.hasSuggestions: true property. This allows ESLint to understand what a rule’s capabilities are just by inspecting the rule object. Rules that provide suggestions without meta.hasSuggestions: true will cause an error.

Fixable rules now require `meta.fixable` property

In ESLint v7.0.0 and earlier, it was possible to write a rule as a function instead of an object and to provide fixes without specifying a meta.fixable property. Beginning in v8.0.0, ESLint requires all rules that provide fixes to be specified in object format and include meta.fixable: code|whitespace.

Unused disable directives are now fixable

ESLint v8.0.0 will now automatically remove unused disable directives when using the --fix command line flag along with --report-unused-disable-directives.

Line comment directives

ESLint v8.0.0 now allows line comment directives for all directives that previously required block comments.

Stricter rule schema validation

With an upgrade to Ajv 8, ESLint v8.0.0 will have improved error detection for rule schemas. There were several areas where the validation would fail silently with Ajv 6, which could lead to end-user errors that were hard to detect. This stricter validation will help catch more errors earlier in the rule development process.

Removal of undocumented APIs; removal of `CLIEngine` and `linter`

ESLint v8.0.0 defines an exports field to remove access to undocumented internal APIs that some packages were accessing.

As part of this change, we have removed the deprecated CLIEngine class to encourage adoption of the replacement ESLint class. CLIEngine was deprecated in 2020 and we can’t continue to support it as we move forward with more ambitious features for ESLint.

Additionally, we are removing the linter object as the Linter class allows you to create any number of instances.

When to expect ESLint v8.0.0

We expect the first beta release of ESLint v8.0.0 to be released at the end of June or the beginning of July. At that point, we will gather feedback from the community and fix any outstanding issues that make it difficult for people to upgrade. Availability of the first beta will be announced on this blog and on our Twitter account, so please stay tuned!

ESLint v7.28.0 released

2021-06-04T00:00:00Z

Highlights

`context.getPhysicalFilename()`

Rules can now use the new method getPhysicalFilename() on the context object to get the full path of the file on disk without any code block information.

The difference between getPhysicalFilename and getFilename is observable when ESLint is used with processors:

context.getPhysicalFilename() // "/project/example.md"        - original file
context.getFilename()         // "/project/example.md/0_0.js" - virtual filename assigned to a code block

Features

bb66a3d New: add getPhysicalFilename() method to rule context (fixes #11989) (#14616) (Nitin Kumar)

Enhancements

c545163 Update: support multiline /*eslint-env*/ directives (fixes #14652) (#14660) (薛定谔的猫)

Bug Fixes

1f048cb Fix: no-implicit-coercion false positive with String() (fixes #14623) (#14641) (Milos Djermanovic)
e44ce0a Fix: no-duplicate-imports allow unmergeable (fixes #12758, fixes #12760) (#14238) (Soufiane Boutahlil)
e4f111b Fix: arrow-body-style crash with object pattern (fixes #14633) (#14635) (Milos Djermanovic)

Documentation

123fb86 Docs: Add Feedback Needed triage description (#14670) (Nicholas C. Zakas)
2e43dac Docs: fix no-sequences example (#14643) (Nitin Kumar)
958ff4e Docs: add note for arrow functions in no-seq rule (#14578) (Nitin Kumar)
85a2725 Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

1237705 Upgrade: @eslint/eslintrc to 0.4.2 (#14672) (Milos Djermanovic)
8d1e75a Upgrade: glob-parent version in package.json (#14658) (Hamza Najeeb)

Chores

d709abf Chore: fix comment location in no-unused-vars (#14648) (Milos Djermanovic)
ec28b5a Chore: upgrade eslint-plugin-eslint-plugin (#14590) (薛定谔的猫)

ESLint v7.27.0 released

2021-05-21T00:00:00Z

Highlights

The no-restricted-imports rule now allows specifying custom error messages for patterns.

Enhancements

9e9b5e0 Update: no-unused-vars false negative with comma operator (fixes #14325) (#14354) (Nitin Kumar)
52655dd Update: no-restricted-imports custom message for patterns (fixes #11843) (#14580) (Alex Holden)

Documentation

6a2ced8 Docs: Update README team and sponsors (ESLint Jenkins)

Chores

2c0868c Chore: merge all html formatter files into html.js (#14612) (Milos Djermanovic)
afe9569 Chore: use includes instead of indexOf (#14607) (Mikhail Bodrov)
c0f418e Chore: Remove lodash (#14287) (Stephen Wade)
967b1c4 Chore: Fix typo in large.js (#14589) (Ikko Ashimine)
086c1d6 Chore: add more test cases for no-sequences (#14579) (Nitin Kumar)

ESLint v7.26.0 released

2021-05-07T00:00:00Z

Features

0b6a3f3 New: Include XO style guide in eslint --init (#14193) (Federico Brigante)

Enhancements

f071d1e Update: Add automated suggestion to radix rule for parsing decimals (#14291) (Bryan Mishkin)

Bug Fixes

ae6dbd1 Fix: track variables, not names in require-atomic-updates (fixes #14208) (#14282) (Patrick Ahmetovic)
ee3a3ea Fix: create .eslintrc.cjs for module type (#14304) (Nitin Kumar)

Documentation

6791dec Docs: fix example for require-atomic-updates (#14562) (Milos Djermanovic)

Dependency Upgrades

aaf65e6 Upgrade: eslintrc for ModuleResolver fix (#14577) (Brandon Mills)

Chores

6a86e50 Chore: remove loose-parser tests (fixes #14315) (#14569) (Milos Djermanovic)

ESLint v7.25.0 released

2021-04-23T00:00:00Z

Enhancements

5df5e4a Update: highlight last write reference for no-unused-vars (fixes #14324) (#14335) (Nitin Kumar)
41b3570 Update: lint code block with same extension but different content (#14227) (JounQin)

Documentation

0023872 Docs: Add deprecated note to working-with-rules-deprecated page (#14344) (Michael Novotny)
f2babb1 Docs: update pull request template (#14336) (Nitin Kumar)
02dde29 Docs: Fix anchor in ‘docs/developer-guide/working-with-rules.md’ (#14332) (Nate-Wilkins)
eb29996 Docs: add more examples with arrow functions for no-sequences rule (#14313) (Nitin Kumar)

Chores

36fca70 Chore: Upgrade eslump to 3.0.0 (#14350) (Stephen Wade)
59b689a Chore: add node v16 (#14355) (薛定谔的猫)
fb0a92b Chore: rename misspelled identifier in test (#14346) (Tobias Nießen)
07d14c3 Chore: remove extraneous command from lint-staged config (#14314) (James George)

ESLint v7.24.0 released

2021-04-09T00:00:00Z

Highlights

The no-implicit-coercion rule has a new disallowTemplateShorthand option.
The no-multi-assign rule has a new ignoreNonDeclaration option.

Enhancements

f06ecdf Update: Add disallowTemplateShorthand option in no-implicit-coercion (#13579) (Remco Haszing)
b51d077 Update: add ignoreNonDeclaration to no-multi-assign rule (fixes #12545) (#14185) (t-mangoe)

Bug Fixes

c4d8b0d Fix: no-unused-vars ignoreRestSiblings check assignments (fixes #14163) (#14264) (YeonJuan)

Documentation

71a80e3 Docs: fix broken links in Node.js API docs toc (#14296) (u-sho (Shouhei Uechi))
bd46dc4 Docs: Fix incorrect reference to “braces” in arrow-parens (#14300) (emclain)
0d6235e Docs: update header in max-lines (#14273) (Shinigami)
70c9216 Docs: Update issue triage to include blocked column (#14275) (Nicholas C. Zakas)
abca186 Docs: Fix typo in suggestions section (#14293) (Kevin Partington)
147fc04 Docs: Fix repro:needed label in bug report template (#14285) (Milos Djermanovic)
e1cfde9 Docs: Update bug report template (#14276) (Nicholas C. Zakas)
c85c2f1 Docs: Add fatal to Node.js API LintMessage type (#14251) (Brandon Mills)

Chores

0c346c8 Chore: ignore pnpm-lock.yaml (#14303) (Nitin Kumar)
c981fb1 Chore: Upgrade mocha to 8.3.2 (#14278) (Stephen Wade)

ESLint v7.23.0 released

2021-03-26T00:00:00Z

Highlights

The no-sequences rule has a new option allowInParentheses.

Enhancements

687ccae Update: add option “allowInParentheses” to no-sequences (fixes #14197) (#14199) (Daniel Rentz)
43f1685 Update: --quiet should not supress --max-warnings (fixes #14202) (#14242) (Milos Djermanovic)
8984c91 Update: eslint --env-info output os info (#14059) (薛定谔的猫)

Bug Fixes

28583eb Fix: no-mixed-operators false positives with ? : (fixes #14223) (#14226) (Milos Djermanovic)
a99eb2d Fix: Clarify line breaks in object-curly-newline (fixes #14024) (#14063) (armin yahya)

Documentation

909c727 Docs: Add valid example that shows vars in a block scope (#14230) (Ed S)
ebd7026 Docs: Fix typo (#14225) (Greg Finley)

Chores

49d1697 Chore: Upgrade eslint-plugin-jsdoc to v25 and remove --legacy-peer-deps (#14244) (Brandon Mills)

ESLint v7.22.0 released

2021-03-12T00:00:00Z

Enhancements

f62ec8d Update: throw error when fix range is invalid (#14142) (Jacob Bandes-Storch)
5ad91aa Update: report es2021 globals in no-extend-native (refs #13602) (#14177) (Milos Djermanovic)

Documentation

3a432d8 Docs: Improve documentation for indent rule (#14168) (Serkan Özel)
3ba029f Docs: Remove Extraneous Dash (#14164) (Danny Hurlburt)
ddf361c Docs: Fix Formatting (#14154) (Danny Hurlburt)
a8df03e Docs: Clarify triage process (#14117) (Nicholas C. Zakas)

Dependency Upgrades

0eecad2 Upgrade: Update lodash in package.json to V 4.17.21 (#14159) (Basem Al-Nabulsi)

Chores

c295581 Chore: remove leftover JSDoc from lint-result-cache (#14176) (Milos Djermanovic)
0d541f9 Chore: Reduce lodash usage (#14178) (Stephen Wade)
459d821 Chore: upgrade dependencies of browser test (#14127) (Pig Fang)

ESLint v7.21.0 released

2021-02-27T00:00:00Z

Highlights

The new --cache-strategy CLI option can improve how ESlint detects changed files by looking at either file metadata or contents.

Features

08ae31e New: Implement cacheStrategy (refs eslint/rfcs#63) (#14119) (Manu Chambon)

Enhancements

5e51fd2 Update: do not ignore symbolic links (fixes #13551, fixes #13615) (#14126) (Pig Fang)

Bug Fixes

b8aea99 Fix: pluralize ‘line’ to ‘lines’ in max-lines-per-function description (#14115) (Trevin Hofmann)

Dependency Upgrades

3cd5440 Upgrade: @eslint/eslintrc to 0.4.0 (#14147) (Brandon Mills)
c0b8c71 Upgrade: Puppeteer to 7.1.0 (#14122) (Tim van der Lippe)

Chores

87c43a5 Chore: improve a few comments and fix typos (#14125) (Tobias Nießen)

Nx becomes ESLint gold sponsor

2021-02-18T00:00:00Z

We are happy to share that Nx has become an ESLint gold sponsor, donating $1,000 each month for the ongoing maintenance and development of ESLint! Nx is a front-end focused set of tools for working with web applications, with a special focus on monorepo setups.

Here’s what the folks at Nx had to say about ESLint:

“Nx uses ESLint to enforce code quality, library boundaries, and project visibility constraints. ESLint makes Nx more powerful, so on behalf of the Nx.dev community, we’re proud to do our part and sponsor ESLint’s continued success!” – Jeff Cross, Co-founder and Principal Architect at Nrwl

“We help many companies build large systems using Nx. To keep them maintainable, it’s important to follow community and org-specific best practices, and ESLint makes it easy.” – Victor Savkin, Co-founder at Nrwl

ESLint is grateful for the support of the Nx team and we are putting these funds to work by paying more contributors to help maintain and develop ESLint. Due to the support of companies like Nx, ESLint is well-positioned to continue being actively maintained for the foreseeable future.

ESLint v7.20.0 released

2021-02-12T00:00:00Z

Highlights

The no-unused-expressions rule has a new option enforceForJSX to flag unused JSX elements.
The following selectors have been updated to support JSX and custom parsers: :first-child, :last-child, :nth-child(n), :nth-last-child(n), sibling ~, and adjacent sibling +. All selectors now support JSX and custom parsers.

Enhancements

ad90761 Update: add enforceForJSX option to no-unused-expressions rule (#14012) (Duncan Beevers)

Bug Fixes

9d6063a Fix: Crash with esquery when using JSX (fixes #13639) (#14072) (Yosuke Ota)
d6c84af Fix: --init autoconfig shouldn’t add deprecated rules (fixes #14017) (#14060) (Milos Djermanovic)
9b277a1 Fix: Support ENOTDIR error code in the folder existence checking utility (#13973) (Constantine Genchevsky)

Documentation

f4ac3b0 Docs: fix sibling selector descriptions (#14099) (Milos Djermanovic)
a0871f1 Docs: Triage process (#14014) (Nicholas C. Zakas)
b4e2af5 Docs: Add more fields to bug report template (#14039) (Nicholas C. Zakas)

Dependency Upgrades

7aeb127 Upgrade: pin @babel/code-frame@7.12.11 (#14067) (Milos Djermanovic)

cb27b0a Build: package.json update for eslint-config-eslint release (ESLint Jenkins)

ESLint v7.19.0 released

2021-01-30T00:00:00Z

Highlights

With this release, we’re excited to publish our revamped configuration guide. Technical writer Khawar Latif Khan spent the last several months since our Google Season of Docs project announcement digging into and improving what used to be a single dense page. The new documentation is logically organized with readability improvements throughout. Thank you Khawar!

Enhancements

ce7f061 Update: add shadowed variable loc to message in no-shadow (fixes #13646) (#13841) (t-mangoe)
c60e23f Update: fix let logic in for-in and for-of loops in no-extra-parens (#14011) (Milos Djermanovic)
1a078b9 Update: check ternary : even if ? was reported in space-infix-ops (#13963) (Milos Djermanovic)
1c309eb Update: fix no-invalid-regexp false negatives with no flags specified (#14018) (Milos Djermanovic)

Bug Fixes

d76e8f6 Fix: no-useless-rename invalid autofix with parenthesized identifiers (#14032) (Milos Djermanovic)
e1da90f Fix: nested indenting for offsetTernaryExpressions: true (fixes #13971) (#13972) (Chris Brody)
fb27422 Fix: extend prefer-const fixer range to whole declaration (fixes #13899) (#14033) (Nitin Kumar)

Documentation

5800d92 Docs: Clarify stylistic rule update policy (#14052) (Brandon Mills)
0ccf6d2 Docs: remove configuring.md (#14036) (Milos Djermanovic)
e0b05c7 Docs: add a correct example to no-unsafe-optional-chaining (refs #14029) (#14050) (armin yahya)
3fc4fa4 Docs: update configuring links (#14038) (Milos Djermanovic)
8561c21 Docs: fix broken links in configuring/README.md (#14046) (Milos Djermanovic)
f6602d5 Docs: Reorganize Configuration Documentation (#13837) (klkhan)
a4fdb70 Docs: Fixed Typo (#14007) (Yash Singh)
f7ca481 Docs: Explain why we disable lock files (refs eslint/tsc-meetings#234) (#14006) (Brandon Mills)

Chores

65bb0ab Chore: Clean up new issue workflow (#14040) (Nicholas C. Zakas)

ESLint v7.18.0 released

2021-01-15T00:00:00Z

Enhancements

f17c3c3 Update: check logical assignment operators in the complexity rule (#13979) (Milos Djermanovic)

Bug Fixes

179a910 Fix: --init crash on question to upgrade/downgrade ESLint (fixes #13978) (#13995) (Milos Djermanovic)
292b1c0 Fix: no-extra-parens false positive with let identifier in for-loop (#13981) (Milos Djermanovic)

Documentation

672deb0 Docs: fix no-invalid-regexp docs regarding ecmaVersion (#13991) (Milos Djermanovic)
f2687e7 Docs: update space-in-parens related rules (#13985) (Chris Brody)
4a38bbe Docs: space-in-parens examples with no arguments etc. (#13987) (Chris Brody)
f6948f6 Docs: Update semantic versioning policy (#13970) (Nicholas C. Zakas)

Dependency Upgrades

e3264b2 Upgrade: @eslint/eslintrc to improve error message for invalid extends (#14009) (Milos Djermanovic)
9250d16 Upgrade: Bump lodash to fix security issue (#13993) (Frederik Prijck)

Chores

78cb483 Chore: test foo( ) with space-in-parens option “always” (#13986) (Chris Brody)
aeba5e5 Chore: fix typo (#13975) (Nitin Kumar)

Google Chrome becomes ESLint gold sponsor

2021-01-13T00:00:00Z

We are happy to share that Google Chrome has become an ESLint gold sponsor sponsor, donating $1,000 each month for the ongoing maintenance and development of ESLint! The Chrome team is well known for supporting web developers around the world through not just developing the browser, but also through resources like web.dev, where they document and explain the latest web technologies.

Here’s what Addy Osmani from the Chrome team told us:

“ESLint has been critical in helping developers write high-quality JavaScript for years. We love that it catches common issues early and often. With a high level of extensibility, ESLint’s ability to let teams enforce custom rules that work for them has been excellent for open-source projects and more. Chrome is happy to sponsor ESLint to help web developers write consistently high-quality code. It’s an essential piece of the modern web development toolkit” – Addy Osmani, Senior Staff Eng. Manager, Chrome

ESLint is grateful for the support of the Chrome team and to Addy for recommending us for the sponsorship. It’s because of support from companies like Google that ESLint is able to receive ongoing maintenance and development by a team of people who work in their spare time.

ESLint v7.17.0 released

2021-01-01T00:00:00Z

Highlights

The multiline-ternary rule is now auto-fixable.

Enhancements

e128e77 Update: check logical assignment in no-constant-condition (#13946) (Milos Djermanovic)
535fe47 Update: use regexpp’s default ecmaVersion in no-control-regex (#13969) (Milos Djermanovic)
0649871 Update: add autofix to rule multiline-ternary (#13958) (薛定谔的猫)

Bug Fixes

83e98cd Fix: use regexpp’s default ecmaVersion in no-invalid-regexp (#13968) (Milos Djermanovic)
f6e7e32 Fix: no-useless-escape wrong loc and fix with CRLF in template elements (#13953) (Milos Djermanovic)
19c69c0 Fix: one-var shouldn’t split declaration if it isn’t in a statement list (#13959) (Milos Djermanovic)

Documentation

7297363 Docs: fix examples for no-multi-str (#13966) (Milos Djermanovic)
e451b96 Docs: update build tool for webpack (#13962) (Sam Chen)

Chores

cc48713 Chore: refactor calculating range and loc in no-useless-escape (#13964) (Milos Djermanovic)
c3e9acc Chore: fix typos (#13960) (YeonJuan)

ESLint v7.16.0 released

2020-12-18T00:00:00Z

Enhancements

a62ad6f Update: fix false negative of no-extra-parens with NewExpression (#13930) (Milos Djermanovic)

Bug Fixes

f85b4c7 Fix: require-atomic-updates false positive across await (fixes #11954) (#13915) (buhi)
301d0c0 Fix: no-constant-condition false positives with unary expressions (#13927) (Milos Djermanovic)
555c128 Fix: false positive with await and ** in no-extra-parens (fixes #12739) (#13923) (Milos Djermanovic)
ab240d4 Fix: prefer-exponentiation-operator invalid autofix with await (#13924) (Milos Djermanovic)

Documentation

d93c935 Docs: update JSON Schema links (#13936) (Milos Djermanovic)
9247683 Docs: Remove for deleted npm run profile script (#13931) (Brandon Mills)
2124e1b Docs: Fix wrong rule name (#13913) (noisyboy25)
26fc12f Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

8d0c93a Upgrade: table@6.0.4 (#13920) (Rouven Weßling)

Chores

dc76911 Chore: Add .pre-commit-hooks.yaml file (#13628) (Álvaro Mondéjar)

Automattic becomes ESLint's first platinum sponsor

2020-12-10T00:00:00Z

We are happy to share that Automattic has become ESLint’s first platinum sponsor, donating $2,000 each month for the ongoing maintenance and development of ESLint! Automattic is the company behind WordPress.com, WooCommerce, Jetpack, Simplenote, Longreads, VaultPress, Akismet, Gravatar, Crowdsignal, Cloudup, Tumblr, and more. Further, Automattic believes in open source and makes a lot of their work public on GitHub and available via the GPL.

Here’s what Automattic engineers told us about ESLint:

“ESLint helps us keep our code consistent and clean across hundreds of developers.”
– Marcus Kazmierczak, Engineering Team Lead, Automattic

“ESLint lets me apply my brain to more important things.”
– Darren Ethier, Engineering Team Lead, Automattic

“Unlike my variables, ESLint is always used.”
– Nadir Seghir, JavaScript Engineer, Automattic

ESLint is honored and excited to be the first project that Automattic has sponsored through Open Collective. Support from companies like Automattic is why ESLint has been able to grow with the JavaScript ecosystem even after seven years in a rapidly changing landscape.

A special thanks to Sarah Gooding of WPTavern for her excellent article, ESLint Maintainers Share Challenges of Funding Open Source Utilities through Sponsorship. We heard from Automattic that it was this article that put ESLint on the team’s radar. We are grateful both for the coverage and the insights shared about funding open source projects.

ESLint v7.15.0 released

2020-12-05T00:00:00Z

Highlights

The new no-unsafe-optional-chaining rule catches cases where short-circuiting ?. in an expression can cause a TypeError.

Features

683ad00 New: no-unsafe-optional-chaining rule (fixes #13431) (#13859) (YeonJuan)

Bug Fixes

cbc57fb Fix: one-var autofixing for export (fixes #13834) (#13891) (Anix)

Documentation

110cf96 Docs: Fix a broken link in working-with-rules.md (#13875) (Anton Niklasson)

Dependency Upgrades

5c11aab Upgrade: @eslint/esintrc and espree for bug fixes (refs #13878) (#13908) (Brandon Mills)
0eb7957 Upgrade: file-entry-cache@6.0.0 (#13877) (Rouven Weßling)

ESLint v7.14.0 released

2020-11-20T00:00:00Z

Highlights

The no-nonoctal-decimal-escape rule has been added. This rule disallows the use of legacy escape sequences \8 and \9 in string literals.

Features

98c00c4 New: Add no-nonoctal-decimal-escape rule (fixes #13765) (#13845) (Milos Djermanovic)

Enhancements

5f09073 Update: fix ‘skip’ options in no-irregular-whitespace (fixes #13852) (#13853) (Milos Djermanovic)

Bug Fixes

2004b7e Fix: enable debug logs for @eslint/eslintrc (fixes #13850) (#13861) (Milos Djermanovic)
d2239a1 Fix: no-useless-constructor crash on bodyless constructor (fixes #13830) (#13842) (Ari Perkkiö)

Documentation

1861b40 Docs: correct the function-call-argument-newline ‘default’ descriptions (#13866) (Trevin Hofmann)
eda0aa1 Docs: no-restricted-imports is only for static imports (#13863) (Robat Williams)
042ae44 Docs: Fix JS syntax and doc URL in working-with-custom-formatters.md (#13828) (Raphael LANG)

Chores

95d2fe6 Chore: remove eslint comment from no-octal-escape tests (#13846) (Milos Djermanovic)
038dc73 Chore: Test on Node.js 15 (#13844) (Brandon Mills)

ESLint v7.13.0 released

2020-11-06T00:00:00Z

Highlights

Per-rule performance metrics can now show more than ten rules. Set the TIMING environment variable to the desired list size or all to display all rules.

$ TIMING=50 eslint lib

$ TIMING=100 eslint lib

$ TIMING=all eslint lib

Features

254e00f New: Configurable List Size For Per-Rule Performance Metrics (#13812) (Bryan Mishkin)

Documentation

6c3c710 Docs: fix broken url in docs (#13815) (SaintMalik)
fb6fcbf Docs: Fix reference to Code of Conduct (#13797) (Tobias Nießen)

ESLint v7.12.1 released

2020-10-26T00:00:00Z

Bug Fixes

aeef485 Fix: Pass internal config paths in FileEnumerator default (fixes #13789) (#13792) (Brandon Mills)

Dependency Upgrades

08f33e8 Upgrade: @eslint/eslintrc to fix rule schema validation (fixes #13793) (#13794) (Brandon Mills)

ESLint v7.12.0 released

2020-10-23T00:00:00Z

Enhancements

cbf3585 Update: skip keyword check for fns in space-before-blocks (fixes #13553) (#13712) (Milos Djermanovic)
bfddced Update: remove suggestion if it didn’t provide a fix (fixes #13723) (#13772) (Milos Djermanovic)
5183b14 Update: check template literal in no-script-url (#13775) (YeonJuan)
603de04 Update: treat all literals like boolean literal in no-constant-condition (#13245) (Zen)
0510621 Update: Fix && vs || short-circuiting false negatives (fixes #13634) (#13769) (Brandon Mills)
67c0605 Update: check computed keys in no-prototype-builtins (fixes #13088) (#13755) (Milos Djermanovic)

Bug Fixes

256f656 Fix: autofix shouldn’t produce template literals with \8 or \9 (#13737) (Milos Djermanovic)
b165aa5 Fix: yoda rule autofix produces syntax errors with adjacent tokens (#13760) (Milos Djermanovic)
3175316 Fix: prefer-destructuring invalid autofix with comma operator (#13761) (Milos Djermanovic)

Documentation

637f818 Docs: add more examples for no-func-assign (fixes #13705) (#13777) (Nitin Kumar)
dee0f77 Docs: add TOC to user-guide/configuring.md (#13727) (metasean)
1457509 Docs: fix broken links in Node.js API docs (#13771) (Laura Barluzzi)
7c813d4 Docs: Fix typo in v7 migration page (#13778) (Yusuke Sasaki)
b025795 Docs: Fix the format option name in the document (#13770) (Hideki Igarashi)
1faeb84 Docs: clarify that space-unary-ops doesn’t apply when space is required (#13767) (Taylor Morgan)

Chores

1a9f171 Chore: Remove more ESLintRC-related files (refs #13481) (#13762) (Nicholas C. Zakas)
17cc0dd Chore: add test case for no-func-assign (refs #13705) (#13783) (Nitin Kumar)
84fd591 Chore: Increase Mocha timeout for copying fixtures (#13768) (Brandon Mills)

ESLint v7.11.0 released

2020-10-09T00:00:00Z

Enhancements

da78fa1 Update: support async arrow fn in function-paren-newline (fixes #13728) (#13729) (Michal Dziekonski)

Bug Fixes

fa9429a Fix: don’t count line after EOF in max-lines (#13735) (Milos Djermanovic)
27f0de6 Fix: account for linebreaks before postfix ++/-- in no-extra-parens (#13731) (Milos Djermanovic)

Documentation

d973675 Docs: Update anchor links to use existing linkrefs (refs #13715) (#13741) (Brandon Mills)
2c6d774 Docs: Fix typos (#13730) (Frieder Bluemle)
ab0ac6c Docs: Fix anchor links (#13715) (Gary Moore)
fe301b8 Docs: Add configuration comments in examples (#13738) (YeonJuan)

Dependency Upgrades

cc468c0 Upgrade: eslint-visitor-keys@2.0.0 (#13732) (Milos Djermanovic)

Chores

23e966f Chore: Refactor CLIEngine tests (refs #13481) (#13709) (Nicholas C. Zakas)

A year of paying contributors: Review

2020-10-07T00:00:00Z

It was in February of 2019 that we announced the launch of the ESLint Collective to fund ESLint’s ongoing development. One of the primary reasons for seeking funding was due to the increasing amount of time required to maintain a project that, as of today, is downloaded over 13 million times each week. We waited until the last quarter of 2019 before we started paying contributors because we wanted to see what our monthly sponsorships would stabilize at and so we’d have some money saved to guarantee a certain amount would be available to pay contributors. Since then, we’ve tried a few different approaches with varying degrees of success and failure, and we’d like to share that experience.

The Technical Steering Committee

The Technical Steering Committee (TSC) is a group of five people who manage the overall direction of the ESLint project. Most of the work that goes into each ESLint release is done by TSC members, including the actual release process itself. Additionally, TSC members review issues and pull requests, as well as representing ESLint at outside events. All that is why we started by figuring out a way to pay TSC members, many of whom have been involved in the project for years prior to ESLint receiving funding.

Here’s what we came up with:

Each TSC member would be paid $50/hour for any contributions to ESLint. Contributions can include actual time working in GitHub, writing code or documentation, attending meetings (both ESLint meetings and external meetings where they represent ESLint), and providing support to the community (over e-mail, chat, etc.).
Payments are capped at $1,000/month for each member. This cap exists primarily to ensure we are saving some portion of our monthly donations and secondarily to dissuade TSC members from spending too much time on the project in addition to their full time jobs. We don’t want to fund burnout.
Later, we added a split of Tidelift funds among the TSC members. We call this the “TSC stipend” and is paid each month to each TSC member regardless of their hourly contributions. The TSC stipend counts towards the $1,000/month limit for each member, and members can invoice the project for the difference between the hours they contributed and the Tidelift amount.

So far, this arrangement has worked exceedingly well. Since starting the TSC payments, we have seen TSC member participation slowly increase. There is something to be said for paying people for valuable work: when the work is explicitly valued, people are more willing to do it. Overall, we would call this part of our program a success.

Dedicated maintainer

Back in November 2019, we announced hiring longtime maintainer Kai Cataldo as a dedicated maintainer. Having recently left his full-time job, Kai wanted to spend more time working on ESLint. We didn’t have the budget to pay him a proper full-time salary for his work, so we agreed on 20 hours per week for $5,000/month, with Kai spending the other 20 hours of his week working on other projects or freelancing.

We tried this for a few months before it became apparent that this arrangement wasn’t sustainable for Kai. While the payments from ESLint were steady, he had to spend a lot of his other 20 hours each week finding ways to make enough money. So, we updated the arrangement to be for 10 hours each week at $2,500, to give Kai more time to find other work while still providing a baseline amount of dedicated ESLint time.

Unfortunately, that arrangement also did not work. Once again, splitting time between his ESLint duties and trying to find other part-time work proved to be a more difficult task than any of us realized, and this month, Kai decided to step down as a dedicated maintainer. He will remain on the TSC and still be eligible for the TSC member payments.

This was a difficult thing for the team to work through, and we think there’s an important lesson about open source sustainability: even though we receive donations, ESLint doesn’t bring in enough to pay maintainers full-time. When that happens, maintainers face a difficult decision: we can try to make part-time development work, but it’s hard to find other part-time work to make up the monthly income we need to make it worthwhile. In some cases, doing the part-time work makes it more difficult to find other work because you are time-constrained in a way that other freelancers are not.

We are currently rethinking how (and if) we’d like to pursue dedicated maintainers in the future given Kai’s experience.

Other Experiments

Along with the TSC payments and hiring a dedicated maintainer, we’ve also tried several other things to distribute payments to more contributors. Our ultimate goal is to be able to pay most, if not all, contributors to ESLint because all contributions are helpful. We still haven’t thought through the details of how this will work, but we have tried several other experiments:

For v7.0.0, we decided to give one-time payments of $250 to several contributors who made outsized contributions to the release. The contributors were both surprised and happy, but we also learned that there are some countries where regulations are very strict regarding what we in the United States call self-employment income. Not everyone was able to participate because of this.
Longtime contributor Kevin Partington had started spending a lot of time helping out community members in our Discord, and to thank him for that, we started paying him $25/hour for any amount of help he provides. If you’ve ever stopped by our Discord and asked for help, there’s a good chance Kevin is the one who helped you out.

Wrapping up

Overall, we are always on the lookout for meaningful and impactful contributions to ESLint so we can reward pay people for those contributions. We will continue to experiment with paying contributors in different ways going forward as we look for ways to make ESLint sustainable for the foreseeable future.

Not everything we tried has worked out, nor did we expect it to, but we firmly believe that it’s worth continuing to work on this problem. Maintaining a project like ESLint takes a lot of work and a lot of contributions from a lot of people. The only way for that to continue is to pay people for their time.

ESLint v7.10.0 released

2020-09-26T00:00:00Z

Highlights

New option ignorePattern in the no-inline-comments rule.

Enhancements

07d9bea Update: Add ignorePattern to no-inline-comments (#13029) (Edie Lemoine)

Bug Fixes

cb44e93 Fix: prefer-destructuring invalid autofix with computed property access (#13704) (Milos Djermanovic)

Documentation

6919fbb Docs: Clarify that ignorePattern should be a string (refs #13029) (#13718) (Brandon Mills)
d79bbe9 Docs: fix typo (#13717) (Alexander Liu)
9b8490e Docs: grammatical error (#13687) (rajdeep)
51674a4 Docs: Add missing quotes (#13714) (Lucio Paiva)
30b76c9 Docs: Clarify package.json requirement in Getting Started (refs #13549) (#13696) (Nicholas C. Zakas)

Dependency Upgrades

46c73b1 Upgrade: eslint-scope@5.1.1 (#13716) (Milos Djermanovic)

Chores

b7b12ba Chore: Move comment to make tests more organized (#13707) (Yusuke Tanaka)
7c34a98 Chore: remove mistakenly added file (#13710) (Milos Djermanovic)

Supporting ESLint's dependencies

2020-09-16T00:00:00Z

When ESLint first started accepting donations, it was with the explicit goal of creating a sustainable future for the project. In the short term, that meant ensuring we could compensate those who spent a significant amount of time on the project, but we always intended that to be a starting point and not an end. There is so much more that goes into open source sustainability and we wanted to be mindful of that as we continued to grow. That’s why we’re excited to announce that we’re now supporting several of the projects that ESLint itself is built upon.

Sponsors choose to support ESLint because they have come to depend on ESLint, and as such, want to ensure that the project continues. Similarly, ESLint is built on top of smaller open source projects, and we feel like it is our responsibility to also help those projects thrive. We’re grateful to our sponsors for helping us get to 50% of our $20,000/month goal, and we feel that it’s time to spread some of that success to our dependencies. As such, we’ve budgeted part of our donations for our dependencies.

Today we are happy to announce that we’ve started donating $100/month to each of the following projects (and one person):

Ajv is a JSON schema validator that ESLint uses to validate configuration.
Eleventy is a Node.js-based static site generator that we use to create eslint.org.
Sindre Sorhus is a prolific open source developer, and ESLint uses several of his modules, including chalk, globals, import-fresh, strip-ansi, and strip-json-comments.

We’re grateful to these projects, and all of our dependencies, for allowing us to build ESLint.

And this is just the start. As our donations continue to grow, we anticipate being able to support more of our dependencies in the future. We envision a future where donations to large open source projects trickle down into their dependencies so the entire open source ecosystem can benefit.

ESLint v7.9.0 released

2020-09-12T00:00:00Z

Enhancements

6f87db7 Update: fix id-length false negatives on Object.prototype property names (#13670) (Milos Djermanovic)

Bug Fixes

3ca2700 Fix: Corrected notice for invalid (:) plugin names (#13473) (Josh Goldberg)
29d1cdc Fix: prefer-destructuring removes comments (refs #13678) (#13682) (Milos Djermanovic)
361ac4d Fix: NonOctalDecimalIntegerLiteral is decimal integer (fixes #13588) (#13664) (Milos Djermanovic)

Documentation

fc5783d Docs: Fix leaky anchors in v4 migration page (#13635) (Timo Tijhof)
f1d07f1 Docs: Provide install commands for Yarn (#13661) (Nikita Baksalyar)
b4da0a7 Docs: fix typo in working with plugins docs (#13683) (啸生)
f260716 Docs: update outdated link (#13677) (klkhan)
5138c91 Docs: add missing eslint directive comments in no-await-in-loop (#13673) (Milos Djermanovic)
17b58b5 Docs: clarify correct example in no-return-await (fixes #13656) (#13657) (Milos Djermanovic)

Chores

9171f0a Chore: fix typo (#13660) (Nitin Kumar)

ESLint v7.8.1 released

2020-09-01T00:00:00Z

Bug Fixes

f542b5d Fix: Update broken @eslint/eslintrc version (fixes #13641) (#13647) (Nicholas C. Zakas)

ESLint v7.8.0 released

2020-08-31T00:00:00Z

Highlights

Support for logical assignment operators and numeric separators has landed in ESLint! To enable linting this syntax, please set ecmaVersion to 2021:

{
    "parserOptions": {
        "ecmaVersion": 2021
    }
}

Enhancements

58abd93 Update: support logical assignments in code path analysis (refs #13569) (#13612) (Milos Djermanovic)
db7488e Update: support logical assignments in core rules (refs #13569) (#13618) (Milos Djermanovic)
88a9ade Update: add es2021 environment (refs #13602) (#13603) (Milos Djermanovic)
0003dc0 Update: support numeric separators (refs #13568) (#13581) (Milos Djermanovic)
96b11a0 Update: Add exceptionPatterns to id-length rule (fixes #13094) (#13576) (sodam)
3439fea Update: support numeric-separator in no-loss-of-precision (refs #13568) (#13574) (Anix)
ed64767 Update: add comment to message in no-warning-comments (fixes #12327) (#13522) (Anix)
66442a9 Update: Add no-magic-numbers ‘ignoreDefaultValues’ option (#12611) (Dieter Luypaert)

Documentation

3729219 Docs: Update Step 1 of Development Environment documentation (klkhan)
483bf7f Docs: fix examples in object-curly-newline (#13605) (Soobin Bak)
1c35d57 Docs: Remove stale Keybase 2FA instructions (#13622) (Brandon Mills)
4111d21 Docs: Fix typo and missing article before noun in docs (#13611) (Patrice Sandhu)
b487164 Docs: add exponentiation operators to operator-assignment documentation (#13577) (Milos Djermanovic)

Dependency Upgrades

091e52a Upgrade: espree@7.3.0 (refs #13568) (#13609) (Kai Cataldo)

Chores

a320324 Chore: Test formatted integers in no-dupe-keys (refs #13568) (#13626) (Brandon Mills)
82669fa Chore: Extract some functionality to eslintrc (refs #13481) (#13613) (Nicholas C. Zakas)
bdb65ec Chore: add 3rd party parsers in BUG_REPORT template (#13606) (YeonJuan)
f954476 Chore: add common 3rd party parsers to issue template (#13596) (Kai Cataldo)
2bee6d2 Chore: Mark config-related files (refs #13481) (#13597) (Nicholas C. Zakas)

Announcing ESLint's public roadmap

2020-08-28T00:00:00Z

When ESLint first started accepting donations, we listed several ways that the project intended to spend the money donated:

Paying team members for maintenance and development. We hired our first part-time maintainer, Kai Cataldo, and started paying TSC members on a per-hour basis up to $1,000 each month (the maximum we can afford at the moment).
Rewarding contributions from the community. We have given spot bonuses to people who have made significant contributions to ESLint.
Improve documentation. We are participating in the 2020 Google Season of Docs to improve our documentation.
Better communication and support. Paying team members has allowed us to participate in the monthly TC39 tooling meeting and allowed us to pay contributors to help answer questions both in GitHub and in Discord.
Developing a Roadmap. Today, we are announcing our first public roadmap!

That last bullet point, developing a roadmap, is something we’ve been working hard to figure out for several months. Paying contributors has helped give us insights into how much development time we have each month and what we can reasonably expect in the future. Our roadmap is published as a GitHub project so you can check to see the status of everything we’re working on. Here’s an overview:

New configuration system. We’ve been designing a new configuration system for the past year that is simpler and will hopefully both speed up ESLint as well as make creating plugins and shareable configs easier. (issue)
Google Season of Docs participation. The Season of Docs program takes several months to complete and will focus on overhauling the configuration documentation. (issue)
Support switching repo branches from master to main. In the long term, we will be switching the primary branch in each repo and need to update our tooling to support it. (issue)
Lint files in parallel. A long-time desire of the community, we are working towards finally allowing you to lint multiple files in parallel to speed up your linting process. (issue)

Items on the roadmap are large in scale and will take a significant amount of time to complete. Each item is something the team is committed to delivering within the next year, and as such, has a TSC member assigned to complete it. New items may be added any time the TSC decides to accept a feature and we have at least one TSC member committed to implementing it.

We hope that this public roadmap will help us explain more about how our resources are allocated on an ongoing basis and just how your donations are contributing to the maintenance and development of ESLint.

Introducing the ESLint Google Season of Docs project and technical writer

2020-08-19T00:00:00Z

This year, ESLint was accepted into the Google Season of Docs (GSoD) program for the first time (thanks, in large part, to our sponsors). The ESLint team has always placed a high value on quality documentation for the project and we came up with a list of projects that we thought could improve our documentation. We received more than 20 applications through GSoD, and after a lot of time grading and reviewing applications, we finally ended up with our technical writer!

It’s our pleasure to introduce Khawar Latif Khan, the 2020 ESLint GSoD technical writer. Here’s a little about Khawar, straight from him:

I am an engineer turned communications specialist from Pakistan, with a passion to create helpful and understandable content. I have a graduate degree in Technical and Professional Communication from North Carolina State University, under the Fulbright Scholarship. During and after my undergraduate degree in Electrical Engineering, I got interested in communicating complex technical knowledge to people in simple terms, an area which most Engineering programs do not pay attention to. This drove me to change my major and serve as a bridge between the creators and the audience of technical information, both interacting with the same content but with different goals.

What interested Khawar in ESLint:

Despite the fact that I have been using open-source software for quite some time, my familiarity with the term is fairly new, similar to my knowledge of linting software. When I started learning Python (through edX), I did wonder how tiny errors can mess the whole code up. I thought it would be nice to have your codes tested, somehow, and get your errors identified, and then I came to know about the term “linting.” I haven’t aptly used linting software yet but I’m sure these will make my life a lot easier in the days to come.

Working with ESLint will not only help me pursue my interests but also strengthen my connection with my engineering knowledge and technical background. My proposed project for ESLint, to reorganize/rewrite the configuration documentation, will focus on conducting a comprehensive content audit, improving the information architecture, and to make the content both useful and reusable. With the guidance of experienced personnel working at ESLint and a collaborative environment, I believe, will add great value to the documentation of ESLint.

Khawar submitted a proposal for reorganizing and rewriting our configuration documentation, which right now contains a lot of information without a lot of structure. His proposal included a comprehensive plan for addressing the documentation, separated into these steps:

Conducting a comprehensive content audit
Create an Information Architecture to understand the flow of information
Improve the Information Architecture to reorganize the documentation
Identify links and references between different sections of the content
Rewrite/Edit parts of the documentation, if necessary to meet the reconfiguration requirements
Ensure the content is flexible and reusable

This proposal contained pages of information related to how each step will progress and how long each step is anticipated to take. This level of detail made us feel comfortable that Khawar understood the project’s goals and the amount of work involved.

Khawar’s ESLint mentor will be Kai Cataldo. Kai is ESLint’s first paid dedicated maintainer, and having his time available is what allowed us to participate in GSoD this year. (Just one of the ways in which your donations benefit the project.) Kai will work directly with Khawar to get him up to speed on the project and guide him through the process of updating the configuration documentation.

We are very excited to be participating in GSoD for the first time and grateful to Khawar for taking this project on. Hopefully, this won’t be the last time the ESLint project is able to participate in GSoD and we look forward to sharing the results of this year’s project in the future.

ESLint v7.7.0 released

2020-08-14T00:00:00Z

Highlights

In ESLint v7.3.0, we released a change to the comma-dangle rule that disallowed having multiple options in the rule’s configuration. Our semantic versioning policy allows for changes that may introduce new errors in semver-minor releases if the change is considered a bug fix and, at the time, we decided that this change fell under that category. After discussing internally whether this was the correct application of our policy or not, we have decided to update our semantic versioning policy to include rule schemas as part of the public API and to revert this change in this release.

Enhancements

b46f3ee Update: allowFunctionParams option in no-underscore-dangle (fixes 12579) (#13545) (Sunghyun Cho)

Bug Fixes

4e0b672 Fix: revert “Update: disallow multiple options in comma-dangle schema” (#13564) (Kai Cataldo)
254990e Fix: indent for async arrow functions (fixes #13497) (#13544) (Anix)

Documentation

26aa245 Docs: clarify “case” specifier in padding-line-between-statements (#13562) (Milos Djermanovic)
082891c Docs: Update semantic versioning policy (#13563) (Nicholas C. Zakas)

Chores

9124a15 Chore: remove leche (fixes #13287) (#13533) (Mark de Dios)

Microsoft donates $10,000 to ESLint as first FOSS Fund recipient

2020-08-13T00:00:00Z

We are happy to share that Microsoft has donated $10,000 to the ESLint project as part of their FOSS Fund. Similar to the Indeed FOSS Contributor Fund and Salesforce FOSS Contributor Fund, the Microsoft FOSS Fund donates $10,000 to qualifying open source projects each quarter. Microsoft employees who have contributed to an open source project that is both used by Microsoft and not an official Microsoft project may nominate and vote on potential project recipients. ESLint is honored to be the first recipient from the Microsoft FOSS Fund!

Here’s what Microsoft’s Jan Pilzer and Steve Faulkner, who nominated ESLint, had to say:

“When I started working in JavaScript professionally many years ago, I realized there was potential of hidden errors and hard to detect problems. Looking into ways to improve the situation for me and my teams, I used various linting tools and was immediately captured by the potential and power of ESLint when it was created. Then and now, ESLint is an incredibly important tool in any JavaScript project I work on. It is the tool that makes large-scale web development possible and enjoyable for all developers.” – Jan Pilzer, Software Engineer, Microsoft

“ESLint has become a critical part of our development tooling at Microsoft. It is as foundational as type checks or unit tests. Without it, we could not ship quality JavaScript and TypeScript code.” - Steve Faulkner, Senior Software Engineer, Microsoft

We are grateful to Jan and Steve for nominating ESLint, and to all of the Microsoft employees who voted for ESLint. Already because of donations like these, ESLint has been able to hire our first part-time maintainer and convert our website from Jekyll to Eleventy. Financial support from companies like Microsoft, Salesforce, and Indeed are what will allow ESLint to be maintained and serve the JavaScript community for the foreseeable future.

Making ESLint more inclusive

2020-08-10T00:00:00Z

From its beginning, the ESLint project has sought to be a place that is welcoming and inclusive of everyone. We adopted a code of conduct before doing so was common (even before we joined the jQuery Foundation, now the OpenJS Foundation) and the project has been maintained by a group of developers from all around the world, representing a variety of ethnicities, cultures, and countries. Even so, we understand that inclusivity is a process that must be adapted as we learn and grow. There is always some way to be more welcoming, and today we’re happy to share with you some of our recent efforts.

Eliminating problematic terminology

One of the areas where we’ve made changes in the project is through the use of more inclusive terminology. We recently did an audit of our codebase to look for words with negative connotations. In doing so, we discovered that we had a few instances of the word “blacklist” in the project, not just inside of code but also in the name of the id-blacklist rule.

In v7.4.0 we renamed the id-blacklist rule to id-denylist while providing a fallback so existing ESLint configs wouldn’t break. In v7.5.0 we officially deprecated the id-blacklist rule. It’s our policy not to remove deprecated rules, but we will no longer be maintaining the id-blacklist rule. Any further changes will be made only to the id-denylist rule.

Going forward, we will be avoiding the use of the following terms:

Blacklist
Whitelist
Master
Slave

While not all of these words trace back to racist origins, they do all have negative connotations that can make people uncomfortable and perpetuate unconscious bias. We want ESLint to be a project that everyone is comfortable participating in, and proud of contributing to, and using more inclusive language helps.

What about the master branch?

Like many open source projects, our primary development branch is called master. We are in the process of transitioning each repository to use main as the primary development branch. This will be a gradual rollout as we work through our least active repositories towards eslint, our most active repository. A large amount of our infrastructure tooling assumes that master is the primary development branch, so it will take us some time and we may need to wait for the GitHub tooling to complete this work.

Moving forward

We want everyone to feel empowered to contribute to ESLint, and to know that when they do, they feel welcome, safe, and included. This latest small action is just a part of our ongoing effort to more inclusive, and we hope other open source projects will do the same.

Salesforce donates $10,000 to ESLint

2020-08-06T00:00:00Z

We are happy to share that Salesforce has donated $10,000 to the ESLint project as part of their FOSS Contributor Fund. The FOSS Contributor Fund donates $10,000 to qualifying open source projects each quarter. Salesforce employees who have contributed to an open source project nominate and vote on potential project recipients. For this quarter, ESLint was selected as the recipient. (Read about it on the Salesforce Blog, too.)

Here’s what Médédé Raymond KPATCHAA, who nominated ESLint, had to say:

“ESLint is an extremely useful tool for any JavaScript project. This tool allows us to set up consistent code formatting rules adopted by the whole team from the beginning of the project, greatly facilitates code reviews, and makes it easy to integrate new developers into the team. I know I am not alone in appreciating its flexibility and ease-of-use.” – Médédé Raymond KPATCHAA, Technical Architect, Salesforce

We are grateful to Médédé for nominating ESLint this quarter and to the Salesforce employees who voted for ESLint. Financial support from companies like Salesforce is why ESLint has been able to keep up with the changing JavaScript ecosystem for the past seven years.

ESLint v7.6.0 released

2020-07-31T00:00:00Z

Highlights

`RuleTester` requires `meta.fixable` for fixable rules

Fixable rules are required to have a meta.fixable property. A bug in the RuleTester class (which is intended to help plugin authors write and test custom rules) was recently surfaced in which fixable rules that do not export metadata (the meta property) are not validated for the existence of a meta.fixable property, while rules that do export meta are.

This has been fixed in this release! Unfortunately, this can lead to new errors being reported by the RuleTester for rules that apply fixes and are missing a meta property. Please feel free to stop by our help channel if you need assistance resolving this issue.

Enhancements

ecb2b73 Update: require meta for fixable rules in RuleTester (refs #13349) (#13489) (Milos Djermanovic)
e71e298 Update: Change no-duplicate-case to comparing tokens (fixes #13485) (#13494) (Yosuke Ota)

Bug Fixes

318fe10 Fix: Do not output undefined as line and column when it’s unavailable (#13519) (haya14busa)
16b10fe Fix: Update the chatroom link to go directly to help channel (#13536) (Nicholas C. Zakas)

Documentation

6fb4edd Docs: fix broken links in developer guide (#13518) (Sam Chen)
6c4aea4 Docs: add ECMAScript 2020 to README (#13510) (Milos Djermanovic)

ESLint v7.5.0 released

2020-07-18T00:00:00Z

Highlights

Optional Chaining Support

Support for optional chaining has landed in ESLint!

const maybeProp = obj.first?.second;

The default parser and built-in rules will support this syntax when you enable parserOptions.ecmaVersion: 2020 in your configuration:

{
    "parserOptions": {
        "ecmaVersion": 2020
    }
}

Deprecating `id-blacklist`

id-blacklist has been deprecated and replaced with id-denylist. We renamed id-blacklist to id-denylist in the previous release (v7.4.0), which unfortunately led to some unintended breakages in the ESLint ecosystem. In this release, we have added back the id-blacklist rule and have marked it as deprecated. If you are currently using id-blacklist, we recommend switching to id-denylist to ensure you receive bug fixes and updates to the rule in future releases.

Enhancements

6ea3178 Update: optional chaining support (fixes #12642) (#13416) (Toru Nagashima)
f4d7b9e Update: deprecate id-blacklist rule (#13465) (Dimitri Mitropoulos)
c8f9c82 Update: Improve report location no-irregular-whitespace (refs #12334) (#13462) (Milos Djermanovic)
0af1d28 Update: add allowSeparatedGroups option to sort-imports (fixes #12951) (#13455) (Milos Djermanovic)
1050ee7 Update: Improve report location for no-unneeded-ternary (refs #12334) (#13456) (Milos Djermanovic)
b77b420 Update: Improve report location for max-len (refs #12334) (#13458) (Milos Djermanovic)

Bug Fixes

a96bc5e Fix: arrow-body-style fixer for in wrap (fixes #11849) (#13228) (Anix)
095194c Fix: add end location to reports in object-curly-newline (refs #12334) (#13460) (Milos Djermanovic)
10251bb Fix: add end location to reports in keyword-spacing (refs #12334) (#13461) (Milos Djermanovic)

Documentation

885a145 Docs: clarify behavior if meta.fixable is omitted (refs #13349) (#13493) (Milos Djermanovic)
1a01b42 Docs: Update technology sponsors in README (#13478) (Nicholas C. Zakas)
f1cc725 Docs: fix linebreaks between versions in changelog (#13488) (Milos Djermanovic)
61097fe Docs: Update int rule level to string (#13483) (Brandon Mills)
e951457 Docs: fix wording in configuring.md (#13469) (Piper)

Dependency Upgrades

6ed9e8e Upgrade: lodash@4.17.19 (#13499) (Yohan Siguret)
748734f Upgrade: Updated puppeteer version to v4.0.0 (#13444) (odidev)

f2e68ec Build: update webpack resolve.mainFields to match website config (#13457) (Milos Djermanovic)

Chores

540b1af Chore: enable consistent-meta-messages internal rule (#13487) (Milos Djermanovic)
e14a645 Chore: use espree.latestEcmaVersion in fuzzer (#13484) (Milos Djermanovic)

ESLint v7.4.0 released

2020-07-03T00:00:00Z

Highlights

Shortly after the v7.3.0 release, we received an issue that eslint-config-airbnb was breaking because it used Infinity in a rule config. Infinity should have been forbidden by the rule’s option schema, but a bug in Ajv, the JSON schema validator that ESLint uses, incorrectly allowed Infinity when an integer was specified. This was finally caught because the v7.3.0 release included a change that fixed an unrelated issue by serializing rule configs. ESLint expects rule configs to be JSON-serializable for consistency between all supported JSON, YAML, and JS .eslintrc formats, and it relies on this property in the --cache and --print-config command line options.

Updating eslint-config-airbnb to use Number.MAX_SAFE_INTEGER instead of Infinity is the ideal solution but would have taken too long. Since this was the only reported issue and isolated to eslint-config-airbnb rather than end-user configs, we implemented an exception that replaced Infinity with Number.MAX_SAFE_INTEGER and released it in v7.3.1, which allowed us to preserve the unrelated bug fix.

After the v7.3.1 release, we received another issue that an eslint-plugin-unicorn rule was directing users to use regular expression instances, which are not JSON-serializable. Unlike eslint-config-airbnb, where the non-serializable value was isolated to a single dependency, end user configs for eslint-plugin-unicorn include regular expressions, so fixing all of them is not practical.

We’re therefore reverting the original change for the v7.4.0 release and will be finding another solution. This will unblock regular linting for users whose rule configs include non-JSON-serializable values, though the --cache and --print-config command line options may exhibit undefined behavior in those cases. A future major version of ESLint will enforce that rule configs contain only JSON-serializable values, and we anticipate that enhancements to RuleTester will help rule authors prepare their schemas for that.

Enhancements

ff5317e Update: Improve array-callback-return report message (#13395) (Philip (flip) Kromer)
51e42ec Update: Add option “ignoreGlobals” to camelcase rule (fixes #11716) (#12782) (David Gasperoni)
0655f66 Update: improve report location in arrow-body-style (refs #12334) (#13424) (YeonJuan)
d53d69a Update: prefer-regex-literal detect regex literals (fixes #12840) (#12842) (Mathias Schreck)
004adae Update: rename id-blacklist to id-denylist (fixes #13407) (#13408) (Kai Cataldo)

Bug Fixes

ada2c89 Fix: support typescript generics in arrow-parens (fixes #12570) (#13451) (Milos Djermanovic)
89ee01e Fix: Revert config cloning (fixes #13447) (#13449) (薛定谔的猫)
3f51930 Fix: false positive new with member in no-extra-parens (fixes #12740) (#13375) (YeonJuan)
825a5b9 Fix: Clarify documentation on implicit ignore behavior (fixes #12348) (#12600) (Scott Hardin)

Documentation

f21bad2 Docs: fix description for never in multiline-ternary (fixes #13368) (#13452) (Milos Djermanovic)
0a463db Docs: fix no-multiple-empty-lines examples (fixes #13432) (#13433) (Milos Djermanovic)

ESLint v7.3.1 released

2020-06-22T00:00:00Z

The v7.3.0 release included a fix for an unrelated issue that caused a configuration issue in eslint-config-airbnb that had previously gone unnoticed to start failing. ESLint expects configurations to be JSON-serializable, so configurations that use Infinity or other non-JSON-serializable values may cause undefined behavior in some parts of ESLint including caching and the --print-config command line argument. In this case, the use of Infinity was not caught until now due to a gap in the JSON schema validator that ESLint uses for which a fix has been implemented and is awaiting release.

In order to give users time to upgrade to an updated version of eslint-config-airbnb when it becomes available, this v7.3.1 release includes a temporary workaround for Infinity that will allow linting to continue despite the undefined behavior elsewhere.

Bug Fixes

de77c11 Fix: Replace Infinity with Number.MAX_SAFE_INTEGER (fixes #13427) (#13435) (Nicholas C. Zakas)

ESLint v7.3.0 released

2020-06-19T00:00:00Z

Highlights

The new no-promise-executor-return rule prevents returning unreadable values from inside new Promise(...) executors.
The new no-unreachable-loop rule catches loops that are guaranteed to execute only once.
Several rules have been updated to report more accurate source code locations.
Several rule option schemas have been improved to catch configuration typos.

Features

9e1414e New: Add no-promise-executor-return rule (fixes #12640) (#12648) (Milos Djermanovic)
b550330 New: Add no-unreachable-loop rule (fixes #12381) (#12660) (Milos Djermanovic)

Enhancements

638a6d6 Update: add missing additionalProperties: false to some rules’ schema (#13198) (Milos Djermanovic)
949a5cd Update: fix operator-linebreak overrides schema (#13199) (Milos Djermanovic)
09cc0a2 Update: max-lines reporting loc improvement (refs #12334) (#13318) (Anix)
ee2fc2e Update: object-property-newline end location (refs #12334) (#13399) (Anix)
d98152a Update: added empty error array check for false negative (#13200) (Anix)
7686d7f Update: semi-spacing should check do-while statements (#13358) (Milos Djermanovic)
cbd0d00 Update: disallow multiple options in comma-dangle schema (fixes #13165) (#13166) (Milos Djermanovic)
13999d2 Update: curly should check consequent if statements (#12947) (Milos Djermanovic)
6cfbd03 Update: Drop @typescript-eslint/eslint-recommended from eslint --init (#13340) (Minh Nguyen)
2a21049 Update: key-spacing loc changes for extra space (refs #12334) (#13362) (Anix)

Bug Fixes

7fb45cf Fix: clone config before validating (fixes #12592) (#13034) (Anix)

Documentation

9d0186e Docs: Fix changelog versions (#13410) (Tony Brix)
1ee3c42 Docs: On maxEOF with eol-last (fixes #12742) (#13374) (Arthur Dias)
0f1f5ed Docs: Add security policy link to README (#13403) (Nicholas C. Zakas)

Chores

c42e548 Chore: enable exceptRange option in the yoda rule (#12857) (Milos Djermanovic)
796f269 Chore: update eslint-config-eslint’s required node version (#13379) (薛定谔的猫)
7ce7988 Chore: Replace the inquirer dependency with enquirer (#13254) (Selwyn)

ESLint v7.2.0 released

2020-06-05T00:00:00Z

Highlights

ECMAScript 2020 syntax support has landed in ESLint! This release adds support for the following language features in the default parser and core rules:

Nullish coalescing operator
export * as ns from "source"
import.meta

Note: We are aware that optional chaining support is still missing. If you’re interested in following the process of implementing support for this syntax, please subscribe to this ESTree issue.

Enhancements

b735a48 Update: add enforceForFunctionPrototypeMethods option to no-extra-parens (#12895) (Milos Djermanovic)
27ef73f Update: reporter locr of func-call-spacing (refs #12334) (#13311) (Anix)
353bfe9 Update: handle parentheses in multiline-ternary (fixes #13195) (#13367) (Milos Djermanovic)
a7fd343 Update: keyword-spacing unexpected space loc improve (refs #12334) (#13377) (Anix)
dd949ae Update: support ?? operator, import.meta, and export * as ns (#13196) (Toru Nagashima)
d5fce9f Update: enable es2020 environment in --init (#13357) (Milos Djermanovic)
b76aef7 Update: Improve report location for template-tag-spacing (refs #12334) (#13203) (Milos Djermanovic)
cb50b69 Update: Improve location for no-mixed-spaces-and-tabs (refs #12334) (#13365) (Milos Djermanovic)

Bug Fixes

e49732e Fix: Ignore import expressions in no-unused-expressions rule (#13387) (Veniamin Krol)
426088c Fix: no-unused-vars updated location to last reference (fixes #13181) (#13354) (Anix)

Documentation

21b1583 Docs: fixed broken hash link for working-with-rules.md (#13386) (Yosuke Ota)

Chores

220349f Chore: Remove duplicate health files (#13380) (Nicholas C. Zakas)
578efad Chore: update no-unused-vars caughtErrors in eslint-config-eslint (#13351) (Milos Djermanovic)
f858f2a Chore: Add Tidelift to funding.yml (#13371) (Nicholas C. Zakas)
c29bd9f Chore: Add breaking/core change link to issue templates (#13344) (Kai Cataldo)

ESLint v7.1.0 released

2020-05-22T00:00:00Z

Features

c636d57 New: no-loss-of-precision (fixes #11279) (#12747) (jmoore914)

Enhancements

df01af1 Update: padded-blocks loc position changes (refs #12334) (#13328) (Anix)
25462b2 Update: block-spacing changed loc for extra (refs #12334) (#13314) (Anix)
a195141 Update: reporting location for semi-spacing (refs #12334) (#13285) (Anix)
b0a6b81 Update: Improve report location for rest-spread-spacing (refs #12334) (#13313) (Milos Djermanovic)
89e1081 Update: Improve report location for linebreak-style (refs #12334) (#13317) (Milos Djermanovic)
742941d Update: added typescript-eslint/recommended configs for init (#13235) (Anix)

Bug Fixes

a93083a Fix: astUtils.getNextLocation returns invalid location after CRLF (#13275) (Milos Djermanovic)
bd3f092 Fix: max-lines-per-function flagging arrow IIFEs (fixes #13332) (#13336) (cherryblossom000)
de0aab9 Fix: report end loc in one-var-declaration-per-line (refs #12334) (#13326) (YeonJuan)
1710296 Fix: no-new-symbol false positive with Symbol as an argument (#13337) (Milos Djermanovic)
cc01451 Fix: arrow-parens no reporting for comments inside (fixes #12995) (#13312) (Anix)
e3e4c41 Fix: fix false positives of no-new-func (#13333) (Pig Fang)
68c8ee3 Fix: Stop path analyzer on unknown nodes (#13305) (Ilya Volodin)
2c778fb Fix: remove custom plugins from replacedBy metadata (#13274) (Kai Cataldo)

Documentation

611c676 Docs: Update new rules policies (#13343) (Nicholas C. Zakas)
0891379 Docs: Document the “correct” way to build an array with values (#13246) (Ed S)
7f14846 Docs: fix broken link in Node.js API docs (#13307) (Kai Cataldo)
1f17533 Docs: Gitter -> Discord URL (refs #13039) (#13308) (Nicholas C. Zakas)
82a448a Docs: improve documentation of no-return-await (#13215) (Linus Unnebäck)

Chores

3a5fbb3 Chore: correct fileoverview doc in accessor-pairs (#13335) (YeonJuan)
88127d7 Chore: remove checkbox from PR template prerequesites (#13330) (Kai Cataldo)
72a4e10 Chore: Mark SourceCode getComments() method as deprecated (fixes #13293) (#13296) (SuperOleg39)
f44a6b4 Chore: fix invalid syntax in require-await tests (#13277) (Milos Djermanovic)

Changes to our rules policies

2020-05-22T00:00:00Z

When ESLint was first created, the idea was to have a small set of 20-30 core rules that could get everyone started, and then to let the community build out its own rules to fill in any remaining gaps. We did, however, continue implementing core rules as it seemed helpful to the point where today there are 280 core rules. At any given time, more than half of open issues and pull requests are related to rules that take up a significant portion of the team’s time.

ESLint now benefits from a thriving ecosystem of rule-focused plugins like eslint-plugin-node, eslint-plugin-import, eslint-plugin-react, and many others. Tools like astexplorer.net and numerous tutorials have made it easier than ever for developers to write their own rules. The core team no longer needs to build up a critical mass of basic rules, so we can prioritize our time on long-awaited core features like parallel linting that will benefit the whole community. We’re making some changes to how we prioritize changes to built-in rules, but as always, if a rule isn’t quite right for your situation, you’re encouraged to modify it as a custom rule for your own project and share it with the rest of the community.

What are the changes?

Going forward, we’re making the following changes to how we deal with rule issues and pull requests:

New rules are limited - we will only accept new rules when they relate to new ECMAScript features that reached stage 4 in the preceding 12 months. The community relies on ESLint to help teach them the correct way to use new language features, and we want to continue doing that. We won’t be accepting new rules that are suggestions or preferences unrelated to new ECMAScript features.
No new rules that only disallow syntax - we already have no-restricted-syntax, which should work for most cases. Otherwise, people can create their own rules. We do have some legacy rules that just disallow syntax (like no-undefined) that we will keep, but we won’t be adding any more.
Stylistic rules are frozen - we won’t be adding any more options to stylistic rules. We’ve learned that there’s no way to satisfy everyone’s personal preferences, and most of the rules already have a lot of difficult-to-understand options. Stylistic rules are those related to spacing, conventions, and generally anything that does not highlight an error or a better way to do something. Update 2021-01-29: We clarified in the README that we will still support newly-added ECMAScript features.
New rule options must be implemented by community members - People can still propose new options for existing core non-stylistic rules, and we will still evaluate them as usual. However, these approved options will need to be implemented by the community and won’t be part of core team’s development roadmap.

What about bugs?

We will still be evaluating all core rules, including stylistic rules, for bugs. If a bug can be verified, we will still fix it as part of our normal maintenance routine.

Thanks for your understanding

We know this is a change to how ESLint is operating, and we appreciate your understanding. ESLint is maintained by one part-time developer and a team of volunteers, and so our bandwidth is limited. We’re making these changes to make better use of the time we have available to maintain the project. If you’d like to help us, please consider contributing to the project or making a donation.

ESLint v7.0.0 released

2020-05-08T00:00:00Z

Highlights

There are several breaking changes in 7.0.0. We’ve created a migration guide to explain the breaking changes and describe how to upgrade.

Dropping support for Node.js v8

Node.js 8 reached EOL in December 2019, and we are officially dropping support for it in this release.

Core rule changes

The ten Node.js/CommonJS rules in core have been deprecated and moved to the eslint-plugin-node plugin.
Several rules have been updated to recognize bigint literals and warn on more cases by default.
eslint:recommended has been updated with a few new rules: no-dupe-else-if, no-import-assign, and no-setter-return.

Improved developer experience

The default ignore patterns have been updated. ESLint will no longer ignore .eslintrc.js and bower_components/* by default. Additionally, it will now ignore nested node_modules directories by default.
ESLint will now lint files with extensions other than .js if they are explicitly defined in overrides[].files - no need to use the --ext flag!
ESLint now supports descriptions in directive comments, so things like disable comments can now be clearly documented!
Additional validation has been added to the RuleTester class to improve testing custom rules in plugins.
ESLint will now resolve plugins relative to the entry configuration file. This means that shared configuration files that are located outside the project can now be colocated with the plugins they require.
Starting in ESLint v7, configuration files and ignore files passed to ESLint using the --config path/to/a-config and --ignore-path path/to/a-ignore CLI flags, respectively, will resolve from the current working directory rather than the file location. This allows for users to utilize shared plugins without having to install them directly in their project.

New `ESLint` class

The CLIEngine class provides a synchronous API that is blocking the implementation of features such as parallel linting, supporting ES modules in shareable configs/parsers/plugins/formatters, and adding the ability to visually display the progress of linting runs. The new ESLint class provides an asynchronous API that ESLint core will now using going forward. CLIEngine will remain in core for the foreseeable future but may be removed in a future major version.

Breaking Changes

4ef6158 Breaking: espree@7.0.0 (#13270) (Kai Cataldo)
78c8cda Breaking: RuleTester Improvements (refs eslint/rfcs#25) (#12955) (Milos Djermanovic)
185982d Breaking: improve plugin resolving (refs eslint/rfcs#47) (#12922) (Toru Nagashima)
48b122f Breaking: change relative paths with --config (refs eslint/rfcs#37) (#12887) (Toru Nagashima)
4af06fc Breaking: Test with an unknown error property should fail in RuleTester (#12096) (Milos Djermanovic)
afa9aac Breaking: class default true computed-property-spacing (fixes #12812) (#12915) (Milos Djermanovic)
7d52151 Breaking: classes default true in accessor-pairs (fixes #12811) (#12919) (Milos Djermanovic)
78182e4 Breaking: Add new rules to eslint:recommended (fixes #12911) (#12920) (Milos Djermanovic)
6423e11 Breaking: check unnamed default export in func-names (fixes #12194) (#12195) (Chiawen Chen)
4293229 Breaking: use-isnan enforceForSwitchCase default true (fixes #12810) (#12913) (Milos Djermanovic)
cf38d0d Breaking: change default ignore pattern (refs eslint/rfcs#51) (#12888) (Toru Nagashima)
bfe1dc4 Breaking: no-dupe-class-members checks some computed keys (fixes #12808) (#12837) (Milos Djermanovic)
c2217c0 Breaking: make radix rule stricter (#12608) (fisker Cheung)
1aa021d Breaking: lint overrides files (fixes #10828, refs eslint/rfcs#20) (#12677) (Toru Nagashima)
b50179d Breaking: Check assignment targets in no-extra-parens (#12490) (Milos Djermanovic)
d86a5bb Breaking: Check flatMap in array-callback-return (fixes #12235) (#12765) (Milos Djermanovic)
cf46df7 Breaking: description in directive comments (refs eslint/rfcs#33) (#12699) (Toru Nagashima)
7350589 Breaking: some rules recognize bigint literals (fixes #11803) (#12701) (Toru Nagashima)
1118fce Breaking: runtime-deprecation on ‘~/.eslintrc’ (refs eslint/rfcs#32) (#12678) (Toru Nagashima)
2c28fbb Breaking: drop Node.js 8 support (refs eslint/rfcs#44) (#12700) (Toru Nagashima)

Features

f9774ec New: Add default-case-last rule (fixes #12665) (#12668) (Milos Djermanovic)
a1d999c New: Add no-useless-backreference rule (fixes #12673) (#12690) (Milos Djermanovic)
985dac3 New: Add no-restricted-exports rule (fixes #10428) (#12546) (Milos Djermanovic)

Enhancements

0b1d65a Update: Improve report location for array-callback-return (refs #12334) (#13109) (Milos Djermanovic)
d3aac53 Update: report backtick loc in no-unexpected-multiline (refs #12334) (#13142) (Milos Djermanovic)
bcafd0f Update: Add ESLint API (refs eslint/rfcs#40) (#12939) (Kai Cataldo)
5c1bdeb Update: Improve report location for getter-return (refs #12334) (#13164) (Milos Djermanovic)
e7c1d4b Update: deprecate Node.js & CommonJS rules (#12898) (Kai Cataldo)
af4472f Update: Improve report location for new-cap (refs #12334) (#13136) (Milos Djermanovic)
a784dac Update: Improve report location newline-per-chained-call (refs #12334) (#13116) (Milos Djermanovic)
5e07574 Update: Improve report location for space-before-function-paren (#13128) (Chiawen Chen)
17e2fe4 Update: Improve error message for fatal fixer errors (#13120) (Brad Zacher)
438dcbb Update: Improve report location for comma-style (refs #12334) (#13111) (Chiawen Chen)
85b7254 Update: no-inner-declarations false negative in non-block (fixes #12222) (#13062) (Anix)
6631ef1 Update: Improve report location for no-empty-function (refs #12334) (#13121) (Milos Djermanovic)
e0f1b6c Update: stricter array index check in no-magic-numbers (fixes #12845) (#12851) (Milos Djermanovic)
362713c Update: Improve report location for template-curly-spacing (#12813) (Milos Djermanovic)
105384c Update: report operator location in operator-linebreak (refs #12334) (#13102) (Milos Djermanovic)
081e240 Update: support globalThis in no-implied-eval (fixes #12670) (#13105) (YeonJuan)
a1370ab Update: Report constructor calls in no-obj-calls (#12909) (Milos Djermanovic)
085979f Update: consider env in no-implied-eval (fixes #12733) (#12757) (YeonJuan)
e90b29b Update: Allow testing Suggestions with data in RuleTester (fixes #12606) (#12635) (Milos Djermanovic)
183e300 Update: support globalThis (refs #12670) (#12774) (YeonJuan)
1299705 Update: acorn version (#13016) (Idan Avrahami)
a5b41a7 Update: no-restricted-modules handle TemplateLiteral (fixes #12926) (#12927) (Michal Piechowiak)
051567a Update: check identifier in array pattern in id-length (fixes #12832) (#12839) (YeonJuan)
9038a29 Update: func-names as-needed false negative with AssignmentPattern (#12932) (Milos Djermanovic)
7747177 Update: report rename id destructuring in id-blacklist (fixes #12807) (#12923) (YeonJuan)
77df505 Update: check renaming identifier in object destructuring (fixes 12827) (#12881) (YeonJuan)
41de9df Update: enforceForLogicalOperands no-extra-boolean-cast (fixes #12137) (#12734) (jmoore914)
1ee6b63 Update: check template literal in yoda (fixes #12863) (#12876) (YeonJuan)
439c833 Update: array-callback-return checks Array.forEach (fixes #12551) (#12646) (Gabriel R Sezefredo)
03a69db Update: check template literal in no-proto, no-iterator (fixes #12801) (#12806) (YeonJuan)
562e784 Update: fix no-magic-numbers false negative with ignoreArrayIndexes (#12805) (Milos Djermanovic)
0460748 Update: check template literal in no-constant-condition (fixes #12815) (#12816) (YeonJuan)
e59d775 Update: Separate pattern/expression options for array-element-newline (#11796) (jacobparish)
f8f115a Update: treat comment tokens in template-curly-spacing (fixes #12744) (#12775) (YeonJuan)
9a93d9e Update: fix no-restricted-imports export * false negative (fixes #12737) (#12798) (Milos Djermanovic)
68becbd Update: fix no-restricted-imports importNames reporting (fixes #12282) (#12711) (Andrey Alexandrov)
ae959b6 Update: report double extra parens in no-extra-parens (fixes #12127) (#12697) (YeonJuan)
b2c6209 Update: fix no-extra-parens CallExpression#callee false negatives (#12743) (Milos Djermanovic)
14b42c3 Update: fix counting jsx comment len in max-len (fixes #12213) (#12661) (YeonJuan)
313f70a Update: add outerIIFEBody: “off” to indent rule (fixes #11377) (#12706) (Kai Cataldo)
3fa39a6 Update: Handle locally unsupported regex in computed property keys (#12056) (Milos Djermanovic)
8f1020f Update: no-void add an option to allow void as a statement (#12613) (Brad Zacher)
bb6cf50 Update: Add offsetTernaryExpressions option for indent rule (#12556) (Adam Stankiewicz)

Bug Fixes

4c0b028 Fix: remove Node.js and CommonJS category from build process (#13242) (Kai Cataldo)
d85e291 Fix: yoda left string fix for exceptRange (fixes #12883) (#13052) (Anix)
8e7a2d9 Fix: func-call-spacing “never” reports wrong message (fixes #13190) (#13193) (Milos Djermanovic)
ebc28d7 Fix: Remove default .js from --ext CLI option (#13176) (Brandon Mills)
c9a5035 Fix: newBasePath should be an absolute path (fixes #12850) (#13078) (Nick Harris)
301b450 Fix: no-extra-parens export default sequence expression false positive (#13096) (Milos Djermanovic)
bfa811c Fix: init error in extending recommended config (fixes #12707) (#12738) (YeonJuan)
7551f0c Fix: no check for shadowed Object (fixes #12809) (#13115) (Anix)
988d842 Fix: add end location to report in no-useless-concat (refs #12334) (#13110) (Milos Djermanovic)
29f32db Fix: Change error message logic for implicit file ignore (fixes #12873) (#12878) (Scott Hardin)
eb1a43c Fix: require-await ignore async generators (fixes #12459) (#13048) (Anix)
920465b Fix: getNameLocationInGlobalDirectiveComment end location (refs #12334) (#13086) (Milos Djermanovic)
ae14a02 Fix: add end location to report in no-extra-bind (refs #12334) (#13083) (Milos Djermanovic)
0c20bc0 Fix: check assignment property target in camelcase (fixes #13025) (#13027) (YeonJuan)
8d50a7d Fix: add end location to report in no-prototype-builtins (refs #12334) (#13087) (Milos Djermanovic)
3e4e7f8 Fix: incorrect logic for required parens in no-extra-boolean-cast fixer (#13061) (Milos Djermanovic)
aef9488 Fix: allow references to external globals in id-blacklist (fixes #12567) (#12987) (Milos Djermanovic)
4955c50 Fix: remove type arguments in prefer-object-spread (fixes #13058) (#13063) (Milos Djermanovic)
dbe357d Fix: check template literal in prefer-numeric-literals (fixes #13045) (#13046) (YeonJuan)
2260611 Fix: added async in allow method in no-empty-function (fixes #12768) (#13036) (Anix)
7224eee Fix: no-plusplus allow comma operands in for afterthought (fixes #13005) (#13024) (Milos Djermanovic)
7598cf8 Fix: Newline before eof when creating config via --init (#12952) (Andreas Lind)
0243549 Fix: camelcase false positive with computed property (fixes #13022) (#13023) (Milos Djermanovic)
6cef0d5 Fix: Check division operator in astUtils.canTokensBeAdjacent (#12879) (Milos Djermanovic)
afde78b Fix: curly removes necessary braces between if and else (fixes #12928) (#12943) (Milos Djermanovic)
4797fb2 Fix: arrow-body-style crash with object literal body (fixes #12884) (#12886) (Milos Djermanovic)
de14d1c Fix: wrap-iife autofix removes mandatory parentheses (#12905) (Milos Djermanovic)
5775b06 Fix: Optionally allow underscores in member names (#11972) (Edgardo Avilés)
0dfc3ff Fix: add end location to report in no-eval (#12960) (Milos Djermanovic)
1f1424c Fix: fix inconsistently works option in no-extra-parens (fixes #12717) (#12843) (YeonJuan)
b5adcaa Fix: make YieldExpression throwable (fixes #12880) (#12897) (YeonJuan)
95e0586 Fix: id-blacklist false positives on renamed imports (#12831) (Milos Djermanovic)
dadc892 Fix: operator-assignment crash on adjacent division assignment (#12844) (Milos Djermanovic)
a9d92f9 Fix: radix rule crash on disabled globals (#12824) (Milos Djermanovic)
533c114 Fix: multiline-comment-style rule add extra space after * (fixes #12785) (#12823) (Karthik Priyadarshan)
80309c3 Fix: no-constant-condition doesn’t introspect arrays (fixes #12225) (#12307) (Sean Gray)
de4fa7c Fix: wrong indent at tagged template in indent (fixes #12122) (#12596) (YeonJuan)
16a1c1f Fix: prefer-object-spread false positives with accessors (fixes #12086) (#12784) (Milos Djermanovic)
0d8c0af Fix: improve report location for computed-property-spacing (#12795) (Milos Djermanovic)
756b95d Fix: id-blacklist should ignore ObjectPatterns (fixes #12787) (#12792) (JP Ramassini)
01ff791 Fix: Display pipe character correctly in test output (#12771) (Brad Zacher)
00ddfff Fix: Windows path parsing for JUnit (fixes #12507) (#12509) (Michael Wall)
1aff21b Fix: no-mixed-spaces-and-tabs reports multiline strings (#12566) (Milos Djermanovic)

Documentation

b5c8d73 Docs: update 7.0.0 migration guide for consistency (#13267) (Kai Cataldo)
356fdb4 Docs: add migration guide (#12692) (Toru Nagashima)
56d2bee Docs: fix typos (#13204) (Nitin Kumar)
516f253 Docs: Adds import example for object-curly-newline rule (refs #12018) (#13177) (Luke Lewis)
b398e0b Docs: add rule comment in prefer-rest-params doc (#13191) (YeonJuan)
c41de38 Docs: fix curly multi-or-nest examples with comments (refs #12972) (#13151) (Milos Djermanovic)
57221d5 Docs: fix eslint comment in no-inner-declarations examples (#13152) (Milos Djermanovic)
5dfd4eb Docs: examples with arrow functions in no-return-assign (fixes #13135) (#13138) (Anix)
adc8fa8 Docs: clarify exceptions in spaced-comment (fixes #13032) (#13126) (Anix)
b228f95 Docs: Update README team and sponsors (ESLint Jenkins)
6c069f9 Docs: Add comments to code block in example (#13089) (Kibeom Kwon)
ee1f053 Docs: Fix typo (#13092) (Max Coplan)
76324ac Docs: Add further reading to rule (#13084) (Max Coplan)
3f7c9bf Docs: clarify variables option in no-use-before-define (fixes #12986) (#13017) (Anix)
9ac5b9e Docs: Clarify node_modules is ignored by default (fixes #13006) (#13054) (Mika Kuijpers)
0de91f3 Docs: removed correct code from incorrect eg (#13060) (Anix)
af7af9d Docs: Update governance (#13055) (Nicholas C. Zakas)
79ac6cd Docs: added less confusing explanation for func-style (fixes #12900) (#13004) (Anix)
b8e20d3 Docs: Mention TypeScript’s compiler check (#12903) (Benny Neugebauer)
e997f32 Docs: Updated arrow-parens for minor grammar issue (#12962) (Tom)
cf14355 Docs: Fix links to custom parsers doc (#12965) (Brandon Mills)
f479f6f Docs: References correct config file name (#12885) (Patrick Kilgore)
8d5c434 Docs: fix category descriptions for site generation (fixes #12894) (#12930) (Kai Cataldo)
05380e6 Docs: Remove claim about semicolons from docs (#12944) (Luke Sikina)
824d235 Docs: add errorOnUnmatchedPattern option to CLIEngine (#12834) (Arthur Denner)
33efd71 Docs: Fix spelling mistakes (#12861) (Bryan Mishkin)
a5b3c5f Docs: Update README team and sponsors (ESLint Jenkins)
d6c313d Docs: add missing eslint comments in prefer-regex-literals examples (#12858) (Milos Djermanovic)
aea1729 Docs: Fix anchor links in Node.js API TOC (#12821) (Matija Marohnić)
02fcc05 Docs: Improve sort-keys (#12791) (Steven Vachon)
25eb703 Docs: fix dead link in max-lines rule docs (#12766) (Christian Bundy)
098b67d Docs: fix minor typo in brace-style.md (#12749) (Marko Kaznovac)
b23ad0d Docs: change a broken link in working-with-rules.md (#12732) (Damien Cassou)

Dependency Upgrades

b98d8bd Upgrade: eslint-release@2.0.0 (#13271) (Kai Cataldo)
3eeae56 Upgrade: some (dev) deps (#13155) (薛定谔的猫)
95e1c70 Upgrade: levn@0.4.1 (fixes #9366) (#13140) (Kai Cataldo)
2111c52 Upgrade: esquery@1.2.0 (#13076) (Milos Djermanovic)
95613d4 Upgrade: espree@6.2.1 (#13026) (Kai Cataldo)
e632c31 Upgrade: several dependencies (#12753) (Toru Nagashima)

8d1b4db Build: changelog update for 7.0.0-rc.0 (ESLint Jenkins)
2531b80 Build: changelog update for 7.0.0-alpha.3 (ESLint Jenkins)
2e8f193 Build: changelog update for 7.0.0-alpha.2 (ESLint Jenkins)
e9f1073 Build: changelog update for 7.0.0-alpha.1 (ESLint Jenkins)
c8c1b2b Build: changelog update for 7.0.0-alpha.0 (ESLint Jenkins)
4e16957 Build: update browser build (#12693) (Toru Nagashima)
827259e Build: package.json update for eslint-config-eslint release (ESLint Jenkins)

Chores

401a687 Chore: fix rules list for prereleases (#13230) (Kai Cataldo)
2ce6bed Chore: added tests for nested arrays (#13145) (Anix)
6b7030b Chore: Run tests on Node.js v14 (#13210) (fisker Cheung)
e13256e Chore: use espree.latestEcmaVersion in config-initializer (#13157) (Kai Cataldo)
e4f57b7 Chore: add nested array tests for array-element-newline (#13161) (Anix)
bc0c02c Chore: added lock files to gitignore (#13015) (Anix)
26267ed Chore: update GitHub Actions (#12984) (Pig Fang)
472025f Chore: update space-before-function-paren in eslint-config-eslint (#12966) (Kai Cataldo)
1907e57 Chore: add Twitter and Open Collective badge (#12877) (Kai Cataldo)
b7f0d20 Chore: Use consistent badge style (#12825) (fisker Cheung)
3734a66 Chore: use ids for messages (#12859) (Gareth Jones)
0cae920 Chore: rename shadowed global (#12862) (Tony Brix)
055b80d Chore: Fix typo in complexity.js (#12864) (Kyle Shevlin)
9f39ef0 Chore: typo in PULL_REQUEST_TEMPLATE.md (#12848) (Balázs Orbán)
a60d5cd Chore: typo in no-irregular-whitespace.js (#12847) (Balázs Orbán)
691d19a Chore: add missing ecmaVersion 2020/11 type value (#12833) (Piotr Błażejewicz (Peter Blazejewicz))
f5b9656 Chore: add test for no-constant-condition (#12836) (Milos Djermanovic)
10a79a6 Chore: Adopt eslint-plugin/require-meta-docs-description internally (#12762) (Bryan Mishkin)
561b6d4 Chore: add prerequisites checklist to PR template (#12790) (Kai Cataldo)
9dfc850 Chore: Refactor to use messageId in a number of rules (#12715) (Brad Zacher)
b77b858 Chore: fix separateRequires tests for one-var rule (#12709) (Milos Djermanovic)
e4df7df Chore: add JSDoc types for RuleTester test cases (#12325) (Chiawen Chen)
4744397 Chore: remove unused code in max-lines-per-function (#12659) (YeonJuan)
39f5a45 Chore: add test cases for for-direction (#12698) (YeonJuan)
b340304 Chore: Add extra test, improve docs (#12492) (Kevin Partington)

ESLint v7.0.0-rc.0 released

2020-04-24T00:00:00Z

Highlights

This release includes a new asynchronous ESLint API for use in Node.js environments. This will allow for the support of ES Module configuration files and plugins and is a prerequisite for implementing parallel linting.
Node.js and CommonJS core rules have been deprecated in favor of eslint-plugin-node.
The reported error location has been fine-tuned in a number of core rules.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@7.0.0-rc.0 --save-dev

Migration Guide

Enhancements

0b1d65a Update: Improve report location for array-callback-return (refs #12334) (#13109) (Milos Djermanovic)
d3aac53 Update: report backtick loc in no-unexpected-multiline (refs #12334) (#13142) (Milos Djermanovic)
bcafd0f Update: Add ESLint API (refs eslint/rfcs#40) (#12939) (Kai Cataldo)
5c1bdeb Update: Improve report location for getter-return (refs #12334) (#13164) (Milos Djermanovic)
e7c1d4b Update: deprecate Node.js & CommonJS rules (#12898) (Kai Cataldo)
af4472f Update: Improve report location for new-cap (refs #12334) (#13136) (Milos Djermanovic)
a784dac Update: Improve report location newline-per-chained-call (refs #12334) (#13116) (Milos Djermanovic)
5e07574 Update: Improve report location for space-before-function-paren (#13128) (Chiawen Chen)
17e2fe4 Update: Improve error message for fatal fixer errors (#13120) (Brad Zacher)
438dcbb Update: Improve report location for comma-style (refs #12334) (#13111) (Chiawen Chen)
85b7254 Update: no-inner-declarations false negative in non-block (fixes #12222) (#13062) (Anix)
6631ef1 Update: Improve report location for no-empty-function (refs #12334) (#13121) (Milos Djermanovic)

Bug Fixes

d85e291 Fix: yoda left string fix for exceptRange (fixes #12883) (#13052) (Anix)
8e7a2d9 Fix: func-call-spacing “never” reports wrong message (fixes #13190) (#13193) (Milos Djermanovic)
ebc28d7 Fix: Remove default .js from --ext CLI option (#13176) (Brandon Mills)
c9a5035 Fix: newBasePath should be an absolute path (fixes #12850) (#13078) (Nick Harris)
301b450 Fix: no-extra-parens export default sequence expression false positive (#13096) (Milos Djermanovic)
bfa811c Fix: init error in extending recommended config (fixes #12707) (#12738) (YeonJuan)
7551f0c Fix: no check for shadowed Object (fixes #12809) (#13115) (Anix)
988d842 Fix: add end location to report in no-useless-concat (refs #12334) (#13110) (Milos Djermanovic)

Documentation

56d2bee Docs: fix typos (#13204) (Nitin Kumar)
516f253 Docs: Adds import example for object-curly-newline rule (refs #12018) (#13177) (Luke Lewis)
b398e0b Docs: add rule comment in prefer-rest-params doc (#13191) (YeonJuan)
c41de38 Docs: fix curly multi-or-nest examples with comments (refs #12972) (#13151) (Milos Djermanovic)
57221d5 Docs: fix eslint comment in no-inner-declarations examples (#13152) (Milos Djermanovic)
5dfd4eb Docs: examples with arrow functions in no-return-assign (fixes #13135) (#13138) (Anix)
adc8fa8 Docs: clarify exceptions in spaced-comment (fixes #13032) (#13126) (Anix)
b228f95 Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

3eeae56 Upgrade: some (dev) deps (#13155) (薛定谔的猫)
95e1c70 Upgrade: levn@0.4.1 (fixes #9366) (#13140) (Kai Cataldo)

Chores

2ce6bed Chore: added tests for nested arrays (#13145) (Anix)
6b7030b Chore: Run tests on Node.js v14 (#13210) (fisker Cheung)
e13256e Chore: use espree.latestEcmaVersion in config-initializer (#13157) (Kai Cataldo)
e4f57b7 Chore: add nested array tests for array-element-newline (#13161) (Anix)

ESLint v7.0.0-alpha.3 released

2020-03-27T00:00:00Z

Highlights

This release contains the following breaking changes:

It also adds support for the following new language features:

Core rules now support globalThis.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@7.0.0-alpha.3 --save-dev

Migration Guide

Breaking Changes

78c8cda Breaking: RuleTester Improvements (refs eslint/rfcs#25) (#12955) (Milos Djermanovic)
185982d Breaking: improve plugin resolving (refs eslint/rfcs#47) (#12922) (Toru Nagashima)
48b122f Breaking: change relative paths with --config (refs eslint/rfcs#37) (#12887) (Toru Nagashima)

Enhancements

e0f1b6c Update: stricter array index check in no-magic-numbers (fixes #12845) (#12851) (Milos Djermanovic)
362713c Update: Improve report location for template-curly-spacing (#12813) (Milos Djermanovic)
105384c Update: report operator location in operator-linebreak (refs #12334) (#13102) (Milos Djermanovic)
081e240 Update: support globalThis in no-implied-eval (fixes #12670) (#13105) (YeonJuan)
a1370ab Update: Report constructor calls in no-obj-calls (#12909) (Milos Djermanovic)
085979f Update: consider env in no-implied-eval (fixes #12733) (#12757) (YeonJuan)
e90b29b Update: Allow testing Suggestions with data in RuleTester (fixes #12606) (#12635) (Milos Djermanovic)
183e300 Update: support globalThis (refs #12670) (#12774) (YeonJuan)
1299705 Update: acorn version (#13016) (Idan Avrahami)

Bug Fixes

29f32db Fix: Change error message logic for implicit file ignore (fixes #12873) (#12878) (Scott Hardin)
eb1a43c Fix: require-await ignore async generators (fixes #12459) (#13048) (Anix)
920465b Fix: getNameLocationInGlobalDirectiveComment end location (refs #12334) (#13086) (Milos Djermanovic)
ae14a02 Fix: add end location to report in no-extra-bind (refs #12334) (#13083) (Milos Djermanovic)
0c20bc0 Fix: check assignment property target in camelcase (fixes #13025) (#13027) (YeonJuan)
8d50a7d Fix: add end location to report in no-prototype-builtins (refs #12334) (#13087) (Milos Djermanovic)
3e4e7f8 Fix: incorrect logic for required parens in no-extra-boolean-cast fixer (#13061) (Milos Djermanovic)
aef9488 Fix: allow references to external globals in id-blacklist (fixes #12567) (#12987) (Milos Djermanovic)
4955c50 Fix: remove type arguments in prefer-object-spread (fixes #13058) (#13063) (Milos Djermanovic)
dbe357d Fix: check template literal in prefer-numeric-literals (fixes #13045) (#13046) (YeonJuan)
2260611 Fix: added async in allow method in no-empty-function (fixes #12768) (#13036) (Anix)
7224eee Fix: no-plusplus allow comma operands in for afterthought (fixes #13005) (#13024) (Milos Djermanovic)
7598cf8 Fix: Newline before eof when creating config via --init (#12952) (Andreas Lind)
0243549 Fix: camelcase false positive with computed property (fixes #13022) (#13023) (Milos Djermanovic)
6cef0d5 Fix: Check division operator in astUtils.canTokensBeAdjacent (#12879) (Milos Djermanovic)

Documentation

6c069f9 Docs: Add comments to code block in example (#13089) (Kibeom Kwon)
ee1f053 Docs: Fix typo (#13092) (Max Coplan)
76324ac Docs: Add further reading to rule (#13084) (Max Coplan)
3f7c9bf Docs: clarify variables option in no-use-before-define (fixes #12986) (#13017) (Anix)
9ac5b9e Docs: Clarify node_modules is ignored by default (fixes #13006) (#13054) (Mika Kuijpers)
0de91f3 Docs: removed correct code from incorrect eg (#13060) (Anix)
af7af9d Docs: Update governance (#13055) (Nicholas C. Zakas)
79ac6cd Docs: added less confusing explanation for func-style (fixes #12900) (#13004) (Anix)

Dependency Upgrades

2111c52 Upgrade: esquery@1.2.0 (#13076) (Milos Djermanovic)
95613d4 Upgrade: espree@6.2.1 (#13026) (Kai Cataldo)

Chores

bc0c02c Chore: added lock files to gitignore (#13015) (Anix)
26267ed Chore: update GitHub Actions (#12984) (Pig Fang)
472025f Chore: update space-before-function-paren in eslint-config-eslint (#12966) (Kai Cataldo)

ESLint v7.0.0-alpha.2 released

2020-02-28T00:00:00Z

Highlights

This release contains the following breaking changes:

Updating default configuration options in core rules.
Updating the rules recommended in eslint:recommended.
Making RuleTester checks stricter.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@7.0.0-alpha.2 --save-dev

Migration Guide

Breaking Changes

4af06fc Breaking: Test with an unknown error property should fail in RuleTester (#12096) (Milos Djermanovic)
afa9aac Breaking: class default true computed-property-spacing (fixes #12812) (#12915) (Milos Djermanovic)
7d52151 Breaking: classes default true in accessor-pairs (fixes #12811) (#12919) (Milos Djermanovic)
78182e4 Breaking: Add new rules to eslint:recommended (fixes #12911) (#12920) (Milos Djermanovic)
6423e11 Breaking: check unnamed default export in func-names (fixes #12194) (#12195) (Chiawen Chen)

Enhancements

a5b41a7 Update: no-restricted-modules handle TemplateLiteral (fixes #12926) (#12927) (Michal Piechowiak)
051567a Update: check identifier in array pattern in id-length (fixes #12832) (#12839) (YeonJuan)
9038a29 Update: func-names as-needed false negative with AssignmentPattern (#12932) (Milos Djermanovic)
7747177 Update: report rename id destructuring in id-blacklist (fixes #12807) (#12923) (YeonJuan)
77df505 Update: check renaming identifier in object destructuring (fixes 12827) (#12881) (YeonJuan)
41de9df Update: enforceForLogicalOperands no-extra-boolean-cast (fixes #12137) (#12734) (jmoore914)

Bug Fixes

afde78b Fix: curly removes necessary braces between if and else (fixes #12928) (#12943) (Milos Djermanovic)
4797fb2 Fix: arrow-body-style crash with object literal body (fixes #12884) (#12886) (Milos Djermanovic)
de14d1c Fix: wrap-iife autofix removes mandatory parentheses (#12905) (Milos Djermanovic)
5775b06 Fix: Optionally allow underscores in member names (#11972) (Edgardo Avilés)
0dfc3ff Fix: add end location to report in no-eval (#12960) (Milos Djermanovic)

Documentation

b8e20d3 Docs: Mention TypeScript’s compiler check (#12903) (Benny Neugebauer)
e997f32 Docs: Updated arrow-parens for minor grammar issue (#12962) (Tom)
cf14355 Docs: Fix links to custom parsers doc (#12965) (Brandon Mills)
f479f6f Docs: References correct config file name (#12885) (Patrick Kilgore)
8d5c434 Docs: fix category descriptions for site generation (fixes #12894) (#12930) (Kai Cataldo)
05380e6 Docs: Remove claim about semicolons from docs (#12944) (Luke Sikina)

What's coming in ESLint v7.0.0

2020-02-20T00:00:00Z

Last week, the Technical Steering Committee (TSC) met to finalize the features for ESLint v7.0.0. This feature set had not yet been locked down even as v7.0.0 work began and so this represented an important milestone that allows us to focus on getting this next major release shipped. You can see everything that is planned for v7.0.0 on our project board.

Significant changes in v7.0.0

The following changes are important to understand as we move towards v7.0.0.

Dropping support for Node.js v8.x

Node.js v8.x was officially end-of-lifed in December 2019 and so v7.0.0 removes support for this version of Node.js.

`ESLint` class replacing `CLIEngine` class

From ESLint’s early days, we have provided a CLIEngine class to allow developers to create ESLint integrations. This class is at the center of things like editor plugins, build tool integrations, and zero-configuration linters. The CLIEngine class powers ESLint itself and has been an important part of the project for many years.

Unfortunately, the CLIEngine has become the major blocker for many new features. Most significantly, because the CLIEngine class works synchronously, it was impossible to do any type of asynchronous operation in the core of ESLint. That limitation meant that features such as parallel linting of files and loading ECMAScript module (ESM) files were impossible to implement.

Several approaches were considered before we decided to replace the CLIEngine class with the new ESLint class (more details). The ESLint class will contain asynchronous methods that will serve as a jumping off point to introducing asynchronous functionality into the core. To begin, the ESLint class will just be a wrapper around CLIEngine and we will systematically start writing new functionality into the ESLint class over time. Eventually, the ESLint and CLIEngine classes will be completely separate.

For v7.0.0, the CLIEngine class will be deprecated but not removed. We expect to remove CLIEngine in a future major release (don’t worry, we’ll give you plenty of notice before doing that).

Deprecating Node.js/CommonJS-specific rules

Managing rules in the core is a significant part of ongoing ESLint maintenance. As the project has grown, so has the number of rules we’ve maintained. We reviewed all of the current rules and decided that the Node.js/CommonJS-specific rules aren’t something that makes sense to include in the core going forward. This is especially true as Node.js moves more towards ESM as the preferred module system.

As such, the following rules will be deprecated in the core:

callback-return
global-require
handle-callback-err
no-buffer-constructor
no-mixed-requires
no-new-require
no-path-concat
no-process-env
no-process-exit
no-restricted-modules

These rules will be moved to the eslint-plugin-node project. We will be recommending that people use the plugin for these rules going forward. The rules will remain in ESLint for v7.0.0 and will be removed in a future major release.

Descriptions in directive comments

Directive comment descriptions allow you to leave a note to yourself and other developers as to why you included the comment. For example:

/* eslint-disable no-new -- this class has a side-effect in the constructor. */

You can read more in the RFC.

Warnings for using `~/.eslintrc`

Config files in your home directory were deprecated in v6.7.0 and v7.0.0 will warn when one is used. This feature has long been a source of confusion for ESLint users, especially because ESLint only looks for a config file in the home directory if no other config file is found. The configuration system in ESLint has changed a lot since home directory config files were introduced, and with the additional flexibility we feel there are plenty of other options for configuring ESLint that are clearer than the home directory config file.

Support for home directory config files will be removed in v8.0.0. You can read more in the RFC.

Updating the base path when using `--config` or `--ignore-path`

In versions prior to v7.0.0, ESLint would resolve references inside of config files or ignore files relative to the file location passed to --config or --ignore-path. This didn’t make much sense and was a source of confusion and unexpected behaviors for users. In v7.0.0, config files and ignore files passed using --config or --ignore-path use the current working directory as their base path. You can read more in the RFC.

Plugins loaded from config file directory

In v7.0.0, plugins will be loaded relative to the configs that reference them. You can read more in the RFC.

File extensions in config files

ESLint v7.0.0 now reads the glob patterns in the overrides section of your config to determine which files to lint. Prior to v7.0.0, you would need to provide the --ext command line flag to specify the additional files to lint. You can read more in the RFC.

Updated default ignore patterns

In addition to the current defaults, the default ignore patterns for ESLint will be changed to:

unignore .eslintrc.js
unignore /bower_components/*
ignore node_modules/* in subdirectories

You can read more in the RFC.

Stricter `RuleTester`

The RuleTester class is adding several additional checks to ensure rules are working properly:

Fails if a rule uses the nonstandard node.start or node.end properties, which may not be provided by all parsers that ESLint supports.
Autofix rules must test the output of their fixes.
Tests where the code has a syntax error will now fail.
Tests fail if the test specification contains unknown properties.

You can read more in the RFC.

Installing preview releases of v7.0.0

If you’d like to test v7.0.0 as it’s developed, you can install from npm using the next tag:

npm i eslint@next --save-dev

Preview releases are published to the next tag periodically until the final v7.0.0 release. Keep in mind that preview releases do not contain all of the changes planned for v7.0.0 and are designed primarily to help us discover bugs and problems upgrading from v6.x.

ESLint v7.0.0-alpha.1 released

2020-02-14T00:00:00Z

Highlights

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@7.0.0-alpha.1 --save-dev

Migration Guide

Breaking Changes

4293229 Breaking: use-isnan enforceForSwitchCase default true (fixes #12810) (#12913) (Milos Djermanovic)
cf38d0d Breaking: change default ignore pattern (refs eslint/rfcs#51) (#12888) (Toru Nagashima)
bfe1dc4 Breaking: no-dupe-class-members checks some computed keys (fixes #12808) (#12837) (Milos Djermanovic)
c2217c0 Breaking: make radix rule stricter (#12608) (fisker Cheung)

Enhancements

1ee6b63 Update: check template literal in yoda (fixes #12863) (#12876) (YeonJuan)
439c833 Update: array-callback-return checks Array.forEach (fixes #12551) (#12646) (Gabriel R Sezefredo)
03a69db Update: check template literal in no-proto, no-iterator (fixes #12801) (#12806) (YeonJuan)
562e784 Update: fix no-magic-numbers false negative with ignoreArrayIndexes (#12805) (Milos Djermanovic)
0460748 Update: check template literal in no-constant-condition (fixes #12815) (#12816) (YeonJuan)

Bug Fixes

1f1424c Fix: fix inconsistently works option in no-extra-parens (fixes #12717) (#12843) (YeonJuan)
b5adcaa Fix: make YieldExpression throwable (fixes #12880) (#12897) (YeonJuan)
95e0586 Fix: id-blacklist false positives on renamed imports (#12831) (Milos Djermanovic)
dadc892 Fix: operator-assignment crash on adjacent division assignment (#12844) (Milos Djermanovic)
a9d92f9 Fix: radix rule crash on disabled globals (#12824) (Milos Djermanovic)
533c114 Fix: multiline-comment-style rule add extra space after * (fixes #12785) (#12823) (Karthik Priyadarshan)
80309c3 Fix: no-constant-condition doesn’t introspect arrays (fixes #12225) (#12307) (Sean Gray)

Documentation

f702b1a Docs: Add missing plugin reference (#12796) (Eduard Bardají Puig)
824d235 Docs: add errorOnUnmatchedPattern option to CLIEngine (#12834) (Arthur Denner)
33efd71 Docs: Fix spelling mistakes (#12861) (Bryan Mishkin)
a5b3c5f Docs: Update README team and sponsors (ESLint Jenkins)
d6c313d Docs: add missing eslint comments in prefer-regex-literals examples (#12858) (Milos Djermanovic)
aea1729 Docs: Fix anchor links in Node.js API TOC (#12821) (Matija Marohnić)

Chores

1907e57 Chore: add Twitter and Open Collective badge (#12877) (Kai Cataldo)
b7f0d20 Chore: Use consistent badge style (#12825) (fisker Cheung)
3734a66 Chore: use ids for messages (#12859) (Gareth Jones)
0cae920 Chore: rename shadowed global (#12862) (Tony Brix)
055b80d Chore: Fix typo in complexity.js (#12864) (Kyle Shevlin)
9f39ef0 Chore: typo in PULL_REQUEST_TEMPLATE.md (#12848) (Balázs Orbán)
a60d5cd Chore: typo in no-irregular-whitespace.js (#12847) (Balázs Orbán)
691d19a Chore: add missing ecmaVersion 2020/11 type value (#12833) (Piotr Błażejewicz (Peter Blazejewicz))
f5b9656 Chore: add test for no-constant-condition (#12836) (Milos Djermanovic)
10a79a6 Chore: Adopt eslint-plugin/require-meta-docs-description internally (#12762) (Bryan Mishkin)

ESLint v7.0.0-alpha.0 released

2020-01-17T00:00:00Z

Highlights

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide.

In addition to the breaking changes, we have three new rules:

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@7.0.0-alpha.0 --save-dev

Migration Guide

As there are a lot of changes, we’re working on a migration guide describing the changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Breaking Changes

1aa021d Breaking: lint overrides files (fixes #10828, refs eslint/rfcs#20) (#12677) (Toru Nagashima)
b50179d Breaking: Check assignment targets in no-extra-parens (#12490) (Milos Djermanovic)
d86a5bb Breaking: Check flatMap in array-callback-return (fixes #12235) (#12765) (Milos Djermanovic)
cf46df7 Breaking: description in directive comments (refs eslint/rfcs#33) (#12699) (Toru Nagashima)
7350589 Breaking: some rules recognize bigint literals (fixes #11803) (#12701) (Toru Nagashima)
1118fce Breaking: runtime-deprecation on ‘~/.eslintrc’ (refs eslint/rfcs#32) (#12678) (Toru Nagashima)
2c28fbb Breaking: drop Node.js 8 support (refs eslint/rfcs#44) (#12700) (Toru Nagashima)

Features

f9774ec New: Add default-case-last rule (fixes #12665) (#12668) (Milos Djermanovic)
a1d999c New: Add no-useless-backreference rule (fixes #12673) (#12690) (Milos Djermanovic)
985dac3 New: Add no-restricted-exports rule (fixes #10428) (#12546) (Milos Djermanovic)

Enhancements

e59d775 Update: Separate pattern/expression options for array-element-newline (#11796) (jacobparish)
f8f115a Update: treat comment tokens in template-curly-spacing (fixes #12744) (#12775) (YeonJuan)
9a93d9e Update: fix no-restricted-imports export * false negative (fixes #12737) (#12798) (Milos Djermanovic)
68becbd Update: fix no-restricted-imports importNames reporting (fixes #12282) (#12711) (Andrey Alexandrov)
ae959b6 Update: report double extra parens in no-extra-parens (fixes #12127) (#12697) (YeonJuan)
b2c6209 Update: fix no-extra-parens CallExpression#callee false negatives (#12743) (Milos Djermanovic)
14b42c3 Update: fix counting jsx comment len in max-len (fixes #12213) (#12661) (YeonJuan)
313f70a Update: add outerIIFEBody: “off” to indent rule (fixes #11377) (#12706) (Kai Cataldo)
3fa39a6 Update: Handle locally unsupported regex in computed property keys (#12056) (Milos Djermanovic)
8f1020f Update: no-void add an option to allow void as a statement (#12613) (Brad Zacher)
bb6cf50 Update: Add offsetTernaryExpressions option for indent rule (#12556) (Adam Stankiewicz)

Bug Fixes

de4fa7c Fix: wrong indent at tagged template in indent (fixes #12122) (#12596) (YeonJuan)
16a1c1f Fix: prefer-object-spread false positives with accessors (fixes #12086) (#12784) (Milos Djermanovic)
0d8c0af Fix: improve report location for computed-property-spacing (#12795) (Milos Djermanovic)
756b95d Fix: id-blacklist should ignore ObjectPatterns (fixes #12787) (#12792) (JP Ramassini)
01ff791 Fix: Display pipe character correctly in test output (#12771) (Brad Zacher)
00ddfff Fix: Windows path parsing for JUnit (fixes #12507) (#12509) (Michael Wall)
1aff21b Fix: no-mixed-spaces-and-tabs reports multiline strings (#12566) (Milos Djermanovic)

Documentation

02fcc05 Docs: Improve sort-keys (#12791) (Steven Vachon)
25eb703 Docs: fix dead link in max-lines rule docs (#12766) (Christian Bundy)
098b67d Docs: fix minor typo in brace-style.md (#12749) (Marko Kaznovac)
b23ad0d Docs: change a broken link in working-with-rules.md (#12732) (Damien Cassou)

Dependency Upgrades

e632c31 Upgrade: several dependencies (#12753) (Toru Nagashima)

4e16957 Build: update browser build (#12693) (Toru Nagashima)
827259e Build: package.json update for eslint-config-eslint release (ESLint Jenkins)

Chores

561b6d4 Chore: add prerequisites checklist to PR template (#12790) (Kai Cataldo)
9dfc850 Chore: Refactor to use messageId in a number of rules (#12715) (Brad Zacher)
b77b858 Chore: fix separateRequires tests for one-var rule (#12709) (Milos Djermanovic)
e4df7df Chore: add JSDoc types for RuleTester test cases (#12325) (Chiawen Chen)
4744397 Chore: remove unused code in max-lines-per-function (#12659) (YeonJuan)
39f5a45 Chore: add test cases for for-direction (#12698) (YeonJuan)
b340304 Chore: Add extra test, improve docs (#12492) (Kevin Partington)

ESLint v6.8.0 released

2019-12-20T00:00:00Z

Highlights

The new --no-error-on-unmatched-pattern CLI flag prevents errors when a quoted glob pattern or --ext is not matched.
ESLint now looks for .eslintrc.cjs config files to allow CommonJS-based configs in ES Module-based packages.

Features

1713d07 New: Add no-error-on-unmatched-pattern flag (fixes #10587) (#12377) (ncraley)

Enhancements

5c25a26 Update: autofix bug in lines-between-class-members (fixes #12391) (#12632) (YeonJuan)
05faebb Update: improve suggestion testing experience (#12602) (Brad Zacher)
05f7dd5 Update: Add suggestions for no-unsafe-negation (fixes #12591) (#12609) (Milos Djermanovic)
1600648 Update: Allow $schema in config (#12612) (Yordis Prieto)
acc0e47 Update: support .eslintrc.cjs (refs eslint/rfcs#43) (#12321) (Evan Plaice)
a230f84 Update: include node version in cache (#12582) (Eric Wang)
6e36d12 Update: do not recommend require-atomic-updates (refs #11899) (#12599) (Kai Cataldo)

Bug Fixes

c5c7086 Fix: ignore aligning single line in key-spacing (fixes #11414) (#12652) (YeonJuan)
272e4db Fix: no-multiple-empty-lines: Adjust reported loc (#12594) (Tobias Bieniek)
a258039 Fix: no-restricted-imports schema allows multiple paths/patterns objects (#12639) (Milos Djermanovic)
51f9620 Fix: improve report location for array-bracket-spacing (#12653) (Milos Djermanovic)
45364af Fix: prefer-numeric-literals doesn’t check types of literal arguments (#12655) (Milos Djermanovic)

Documentation

d3e43f1 Docs: Update no-multi-assign explanation (#12615) (Yuping Zuo)
e3c570e Docs: Add example for expression option (#12694) (Arnaud Barré)
6b774ef Docs: Add spacing in comments for no-console rule (#12696) (Nikki Nikkhoui)
ab912f0 Docs: 1tbs with allowSingleLine edge cases (refs #12284) (#12314) (Ari Kardasis)
e9cef99 Docs: wrap {{}} in raw liquid tags to prevent interpolation (#12643) (Kai Cataldo)
e707453 Docs: Fix configuration example in no-restricted-imports (fixes #11717) (#12638) (Milos Djermanovic)

Chores

9986d9e Chore: add object option test cases in yield-star-spacing (#12679) (YeonJuan)
4b3cc5c Chore: enable prefer-regex-literals in eslint codebase (#12268) (薛定谔的猫)
7171fca Chore: refactor regex in config comment parser (#12662) (Milos Djermanovic)
49c1658 Chore: remove bundling of ESLint during release (#12676) (Kai Cataldo)
257f3d6 Chore: complete to move to GitHub Actions (#12625) (Toru Nagashima)
8b65f17 Chore: remove references to parser demo (#12644) (Kai Cataldo)
19194ce Chore: Add tests to cover default object options in comma-dangle (#12627) (YeonJuan)

ESLint v6.7.2 released

2019-11-30T00:00:00Z

Bug Fixes

bc435a9 Fix: isSpaceBetweenTokens() recognizes spaces in JSXText (fixes #12614) (#12616) (Toru Nagashima)
4928d51 Fix: don’t ignore the entry directory (fixes #12604) (#12607) (Toru Nagashima)
ea16de4 Fix: Support tagged template literal generics in no-unexpected-multiline (#11698) (Brad Zacher)

Documentation

b41677a Docs: Clarify suggestion’s data in Working with Rules (refs #12606) (#12617) (Milos Djermanovic)

ESLint v6.7.1 released

2019-11-24T00:00:00Z

Bug Fixes

dd1e9f4 Fix: revert changes to key-spacing due to regression (#12598) (Kai Cataldo)

Documentation

c644b54 Docs: Update README team and sponsors (ESLint Jenkins)

ESLint v6.7.0 released

2019-11-22T00:00:00Z

Highlights

Suggestions API

This release contains a new Suggestions API for rule authors and integrations. You can read more about this exciting new feature here.

`ignorePatterns` in config files

This release adds a new ignorePatterns property in config files (including shareable configs) in order to control the files ESLint ignores. See also documentation.

New Rules

Deprecations

Please note that these deprecated features may be removed in a future major release of ESLint.

Features

312a88f New: Add grouped-accessor-pairs rule (fixes #12277) (#12331) (Milos Djermanovic)
6eaad96 New: Add suggestions API (#12384) (Will Douglas)
1a2eb99 New: new rule no-constructor-return (fixes #12481) (#12529) (Pig Fang)
ca3b2a6 New: ignorePatterns in config files (refs eslint/rfcs#22) (#12274) (Toru Nagashima)
17a8849 New: Add no-dupe-else-if rule (fixes #12469) (#12504) (Milos Djermanovic)
45aa6a3 New: Add no-setter-return rule (fixes #12285) (#12346) (Milos Djermanovic)
41b1e43 New: add option for camelcase (fixes #12527) (#12528) (Pig Fang)
de65de6 New: Add prefer-exponentiation-operator rule (fixes #10482) (#12360) (Milos Djermanovic)
e17fb90 New: allowAfterThisConstructor for no-underscore-dangle (fixes #11488) (#11489) (sripberger)

Enhancements

5c68f5f Update: Add ‘lexicalBindings’ to no-implicit-globals and change messages (#11996) (Milos Djermanovic)
97c745d Update: Report assignment expression location in no-cond-assign (#12465) (Milos Djermanovic)
0f01f3d Update: Check member expressions with this in operator-assignment (#12495) (Milos Djermanovic)
4f8a1ee Update: Add enforceForClassMembers option to no-useless-computed-key (#12110) (ark120202)
41a78fd Update: improve location for semi and comma-dangle (#12380) (Chiawen Chen)
b8030fc Update: deprecate personal config (fixes #11914, refs eslint/rfcs#32) (#12426) (Toru Nagashima)
6503cb8 Update: Fix uglified object align in key-spacing (fixes #11414) (#12472) (YeonJuan)
0f7edef Update: add react plugin config for eslint init (#12446) (Ibrahim Rouis)
448ff1e Update: Report ‘\08’ and ‘\09’ in no-octal-escape (fixes #12080) (#12526) (Milos Djermanovic)
90305e0 Update: Depcrecate isSpaceBetweenTokens() (#12519) (Kai Cataldo)
990065e Update: curly multi-or-nest flagging semis on next line (fixes #12370) (#12378) (cherryblossom000)
7e41355 Update: improve report location for space-infix-ops (#12324) (Chiawen Chen)
94ff921 Update: Add capIsConstructor option to no-invalid-this (fixes #12271) (#12308) (Milos Djermanovic)
c78f4a7 Update: Allow JSX exception in no-inline-comments (fixes #11270) (#12388) (Milos Djermanovic)

Bug Fixes

b336fbe Fix: indent rule with JSX spread props (#12581) (Nathan Woltman)
62c7038 Fix: invalid token checking in computed-property-spacing (fixes #12198) (#12533) (YeonJuan)
62623f9 Fix: preserve whitespace in multiline-comment-style (fixes #12312) (#12316) (Kai Cataldo)
fed20bb Fix: require-await crash on global await (#12571) (Brad Zacher)
40c8c32 Fix: improve report location for object-curly-spacing (#12563) (Milos Djermanovic)
1110045 Fix: ignore marker-only comments in spaced-comment (fixes #12036) (#12558) (Milos Djermanovic)
0afb518 Fix: invalid autofix in function-call-argument-newline (fixes #12454) (#12539) (YeonJuan)
9e29e18 Fix: sourceCode#isSpaceBetweenTokens() checks non-adjacent tokens (#12491) (Kai Cataldo)
bb556d5 Fix: curly multi reports single lexical declarations (fixes #11908) (#12513) (Milos Djermanovic)
ac60621 Fix: unexpected autofix in prefer-const (fixes #12514) (#12521) (YeonJuan)
084a8a6 Fix: no-cond-assign with always option reports switch case clauses (#12470) (Milos Djermanovic)

Documentation

60204a3 Docs: Added another Textmate 2 bundle. (#12580) (Ryan Fitzer)
0a480f8 Docs: Change “Code Conventions” link in pull-requests.md (#12401) (Denis Sikuler)
40791af Docs: clarify ignoreDestructuring option in the camelcase rule (#12553) (Milos Djermanovic)
0286b57 Docs: Clean up Getting Started Guide (#12544) (Nicholas C. Zakas)
5868550 Docs: add notice about function keyword in keyword-spacing (#12524) (Pig Fang)
4e142ea Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

f49f1e0 Upgrade: upgrade optionator to avoid license issue (fixes #11536) (#12537) (Pig Fang)
98e1d50 Upgrade: globals to v12.1.0 (#12296) (Tony Brix)

287ca56 Build: update CI for Node.js 13 (#12496) (Toru Nagashima)

Chores

07d398d Chore: Add GitHub organization to Sponsor button (#12562) (Brandon Mills)
a477707 Chore: Format style guide links so they can be clicked (#12189) (Ivan V)
575a98d Chore: Add funding field to package.json (#12543) (Nicholas C. Zakas)

Funding ESLint's Future: November Update

2019-11-07T00:00:00Z

Back in February, we announced the creation of the ESLint Collective to raise funds for the ongoing maintenance and development of ESLint. Our goal was to raise $20,000 each month to support the project, and since then, we’ve been grateful for contributions from nearly 150 companies, projects, and individuals towards that goal.

We are happy to share that we are currently sponsored at just under $10,000 per month, almost 50% of our goal! At this level, we’ve been able to start paying team members for their time (more about this below), ensuring ESLint gets the ongoing support it needs.

How we’ve used the money

As mentioned above, the most exciting thing we’ve been able to do with the money you’ve donated is pay a team member to work on ESLint part-time. Kai Cataldo has been involved with ESLint for several years and for the past two months has been working part-time on ESLint. Having Kai consistently working on the project has meant faster response times to issues and pull requests, and better coordination across the team. Here’s what Kai said about this experience:

As a long-time maintainer of ESLint, I’m both humbled and grateful to be able to be paid to work on the project. Instead of eking out a few minutes between other activities, it has allowed me to carve out blocks of time to dedicate to consistent, focused work. In practical terms, it has allowed me to better prioritize the time I spend on the project, and I’ve been able to be more active, from finding more time to write code, to reviewing pull requests, to managing bug reports and feature requests from the community. So much of the software we use every day relies on projects like ESLint to deliver value and improve our lives, and the resources we spend on these projects have an enormous ripple effect. Money certainly isn’t everything, but there is a big difference between volunteer work and a job, and investment from the community has in turn allowed me to invest more focused time and energy into ESLint.

– Kai Cataldo, ESLint team member

Our hope is that as we continue raising money, we will be able to bring on at least one more part-time maintainer to keep the ESLint project running smoothly.

What our sponsors are telling us

We also reached out to our sponsors to ask them how they use ESLint internally and why they decided to sponsor the ESLint project. Shopify is one of our more recent sponsors, and here’s what they had to say:

We use ESLint to push developers towards patterns that are better for the long-term maintainability of the codebase. We’ve written many custom rules to avoid vagueness in tests, ensure that all content is translated, prevent code from reaching for implementation details of its dependencies, and much more. We also use great community plugins that offer many additional rules around React, TypeScript, and GraphQL. All of these rules run on every commit, in every app, offering a consistent set of stylistic guidelines no matter what project a developer is working on.

– Chris Sauve, Web Developer at Shopify

One of our initial sponsors, Facebook, also makes use of ESLint internally:

ESLint is a valued part of the JS ecosystem and developer community. ESLint is used in production systems. Thanks to you and the community for all the dedication and hard work.

The FB OSS program supports communities in many ways. Direct community sponsorships is one area where it is experimenting.

– Erik Nakagawa, Head of Open Source at Calibra (Facebook)

Another of our initial sponsors, Salesforce, makes extensive use of ESLint as part of their larger development ecosystem:

We have been using ESLint for many years, specially on our core platform, where it has become one of the most fundamental pieces of our pipeline.

To name some of our most important use cases of ESLint:

We use it to validate and enforce specific rules and semantics every time a customer pushes components to our platform. That helps us scale and guarantee correctness on all the code that we serve.

We use it to give all our developers a recommended set of rules, patterns and stylistic principles that allow us to keep a healthy and maintainable code base.

We use it to guard specific API usages that will prevent the code from running in different conditions or host environments.

We use it to help our customers write performant code, specially in IE11 where we have rules to prevent specific grammar that will transpile down to very inefficient code (ex. async-await, default function parameters).

Given that ESLint is such a core part of our platform and ecosystem, we are really proud to be part of the community by sponsoring and contributing in any way we can to the future of an amazing project.

– Diego Ferreiro Val, Principal Architect at Salesforce

Help us reach our goal

If your company also uses ESLint to find and fix problems in your JavaScript code, please ask them to join these fantastic companies in sponsoring ESLint. (All sponsors above $200 per month get their logos on both the ESLint README and on the homepage of eslint.org.)

ESLint v6.6.0 released

2019-10-25T00:00:00Z

Highlights

Rules can now access context.getCwd() to get the current working directory
The use-isnan rule has a new enforceForIndexOf option
The no-param-reassign rule has a new ignorePropertyModificationsForRegex option
The no-unsafe-negation rule has a new enforceForOrderingRelations option
The no-extra-parens has a new enforceForNewInMemberExpressions option

In addition, we have improved the error report locations for a number of rules with this release.

Features

874fe16 New: pass cwd from cli engine (#12389) (Eric Wang)

Enhancements

39dfe08 Update: false positives in function-call-argument-newline (fixes #12123) (#12280) (Scott O’Hara)
4d84210 Update: improve report location for no-trailing-spaces (fixes #12315) (#12477) (Milos Djermanovic)
c6a7745 Update: no-trailing-spaces false negatives after comments (fixes #12479) (#12480) (Milos Djermanovic)
c6a9a3b Update: Add enforceForIndexOf option to use-isnan (fixes #12207) (#12379) (Milos Djermanovic)
364877b Update: measure plugin loading time and output in debug message (#12395) (Victor Homyakov)
aac3be4 Update: Add ignored prop regex no-param-reassign (#11275) (Luke Bennett)
7dffe48 Update: Enable function string option in comma-dangle (fixes #12058) (#12462) (YeonJuan)
7c8bbe0 Update: enforceForOrderingRelations no-unsafe-negation (fixes #12163) (#12414) (Sam Rae)
349ed67 Update: improve report location for no-mixed-operators (#12328) (Chiawen Chen)
6e7c18d Update: enforceForNewInMemberExpressions no-extra-parens (fixes #12428) (#12436) (Milos Djermanovic)
2d6e345 Update: make isSpaceBetweenTokens() ignore newline in comments (#12407) (YeonJuan)
84f71de Update: remove default overrides in keyword-spacing (fixes #12369) (#12411) (YeonJuan)
18a0b0e Update: improve report location for no-space-in-parens (#12364) (Chiawen Chen)
d61c8a5 Update: improve report location for no-multi-spaces (#12329) (Chiawen Chen)
b962775 Update: no-self-assign should detect member expression with this (#12279) (Tibor Blenessy)

Bug Fixes

0bffe95 Fix: no-misleading-character-class crash on invalid regex (fixes #12169) (#12347) (Milos Djermanovic)
1744fab Fix: operator-assignment removes and duplicates comments (#12485) (Milos Djermanovic)
52ca11a Fix: operator-assignment invalid autofix with adjacent tokens (#12483) (Milos Djermanovic)
0f6d0dc Fix: CLIEngine#addPlugin reset lastConfigArrays (fixes #12425) (#12468) (Toru Nagashima)
49faefb Fix: no-obj-calls false positive (fixes #12437) (#12467) (Toru Nagashima)
b3dbd96 Fix: problematic installation issue (fixes #11018) (#12309) (Toru Nagashima)
89e8aaf Fix: improve report location for no-tabs (#12471) (Milos Djermanovic)
a102eaa Fix: prefer-numeric-literals invalid autofix with adjacent tokens (#12387) (Milos Djermanovic)
51fbbd7 Fix: array-bracket-newline consistent error with comments (fixes #12416) (#12441) (Milos Djermanovic)
e657d4c Fix: report full dot location in dot-location (#12452) (Milos Djermanovic)

Documentation

8233873 Docs: Add note about Node.js requiring SSL support (fixes #11413) (#12475) (Nicholas C. Zakas)
e15e1f9 Docs: fix doc for no-unneeded-ternary rule (fixes #12098) (#12410) (Sam Rae)
02977f2 Docs: Clarify eslint:recommended semver policy (#12429) (Kevin Partington)
97045ae Docs: Fixes object type for rules in “Use a Plugin” (#12409) (Daisy Develops)
24ca088 Docs: Fix typo in v6 migration guide (#12412) (Benjamim Sonntag)
84467c0 Docs: fix wrong max-depth example (fixes #11991) (#12358) (Gabriel R Sezefredo)
3642342 Docs: Fix minor formatting/grammar errors (#12371) (cherryblossom000)
c47fa0d Docs: Fix missing word in sentence (#12361) (Dan Boulet)

Dependency Upgrades

561093f Upgrade: bump inquirer to ^7.0.0 (#12440) (Joe Graham)

Chores

923a8cb Chore: Fix lint failure in JSDoc comment (#12489) (Brandon Mills)
e5382d6 Chore: Remove unused parameter in dot-location (#12464) (Milos Djermanovic)
61749c9 Chore: Provide debug log for parser errors (#12474) (Brad Zacher)
fb633b2 Chore: Add a script for testing with more control (#12444) (Eric Wang)
b094008 Chore: update version parameter name (#12402) (Toru Nagashima)
e5637ba Chore: enable jsdoc/require-description (#12365) (Kai Cataldo)
7ffb22f Chore: Clean up inline directive parsing (#12375) (Jordan Eldredge)
8108f49 Chore: enable additional eslint-plugin-jsdoc rules (#12336) (Kai Cataldo)
b718d2e Chore: update issue template with --eslint-fix flag (#12352) (James George)

ESLint v6.5.1 released

2019-09-30T00:00:00Z

Bug Fixes

447ac87 Fix: no-useless-rename handles ExperimentalRestProperty (fixes #12335) (#12339) (Kai Cataldo)

Documentation

0d3d7d9 Docs: fix typo in no-magic-numbers (#12345) (Josiah Rooney)

ESLint v6.5.0 released

2019-09-29T00:00:00Z

Highlights

We have added a new --env-info CLI option, which provides a lot of information that is useful for GitHub issues.
The use-isnan rule supports a new option, enforceForSwitchCase.
The indent rule now supports JSXFragment nodes.

In addition, many rules that removed comments during autofix have been modified to avoid removing comments. Please open an issue if you find any more cases that need to be fixed.

Features

a7894eb New: add --env-info flag to CLI (#12270) (Kai Cataldo)

Enhancements

73596cb Update: Add enforceForSwitchCase option to use-isnan (#12106) (Milos Djermanovic)
334ca7c Update: no-useless-rename also reports default values (fixes #12301) (#12322) (Kai Cataldo)
41bfe91 Update: Fix handling of chained new expressions in new-parens (#12303) (Milos Djermanovic)
11ae6fc Update: Fix call, new and member expressions in no-extra-parens (#12302) (Milos Djermanovic)
d4f9a16 Update: add support for JSXFragments in indent rule (fixes #12208) (#12210) (Kai Cataldo)

Bug Fixes

d592a24 Fix: exclude \u000d so new line won’t convert to text (fixes #12027) (#12031) (zamboney)
e85d27a Fix: no-regex-spaces false positives and invalid autofix (fixes #12226) (#12231) (Milos Djermanovic)
b349bf7 Fix: prefer-named-capture-group incorrect locations (fixes #12233) (#12247) (Milos Djermanovic)
7dc1ea9 Fix: no-useless-return autofix removes comments (#12292) (Milos Djermanovic)
0e68677 Fix: no-extra-bind autofix removes comments (#12293) (Milos Djermanovic)
6ad7e86 Fix: no-extra-label autofix removes comments (#12298) (Milos Djermanovic)
acec201 Fix: no-undef-init autofix removes comments (#12299) (Milos Djermanovic)
d89390b Fix: use async reading of stdin in bin/eslint.js (fixes #12212) (#12230) (Barrie Treloar)
8316e7b Fix: no-useless-rename autofix removes comments (#12300) (Milos Djermanovic)
f5537b2 Fix: prefer-numeric-literals autofix removes comments (#12313) (Milos Djermanovic)

Documentation

9b86167 Docs: Add new ES environments to Configuring ESLint (#12289) (Milos Djermanovic)
c9aeab2 Docs: Add supported ECMAScript version to README (#12290) (Milos Djermanovic)
2c6bf8e Docs: English fix (#12306) (Daniel Nixon)
2e202ca Docs: fix links in array-callback-return (#12288) (Milos Djermanovic)
e39c631 Docs: add example for CLIEngine#executeOnText 3rd arg (#12286) (Kai Cataldo)
9984c3e Docs: Update README team and sponsors (ESLint Jenkins)

Chores

160b7c4 Chore: add autofix npm script (#12330) (Kai Cataldo)
04b6adb Chore: enable eslint-plugin-jsdoc (refs #11146) (#12332) (Kai Cataldo)
29c12f1 Chore: cache results in runtime-info (#12320) (Kai Cataldo)
f9fc695 Chore: enable default-param-last (#12244) (薛定谔的猫)

ESLint v6.4.0 released

2019-09-13T00:00:00Z

Highlights

Three new rules: no-import-assign, prefer-regex-literals, default-param-last
accessor-pairs and computed-property-spacing rules has been updated with a new option enforceForClassMembers

Features

1c921c6 New: add no-import-assign (fixes #12237) (#12252) (Toru Nagashima)
3be04fd New: Add prefer-regex-literals rule (fixes #12238) (#12254) (Milos Djermanovic)
0313441 New: add rule default-param-last (fixes #11361) (#12188) (Chiawen Chen)

Enhancements

540296f Update: enforceForClassMembers option to accessor-pairs (fixes #12063) (#12192) (Milos Djermanovic)
d3c2334 Update: flag nested block with declaration as error (#12193) (David Waller)
b2498d2 Update: Fix handling of property names in no-self-assign (#12105) (Milos Djermanovic)
1ee61b0 Update: enforceForClassMembers computed-property-spacing (fixes #12049) (#12214) (Milos Djermanovic)
db2a29b Update: indentation of comment followed by semicolon (fixes #12232) (#12243) (Kai Cataldo)
37c0fde Update: Report global Atomics calls in no-obj-calls (fixes #12234) (#12258) (Milos Djermanovic)
e38f5fd Update: fix no-octal-escape false negatives after \0 (#12079) (Milos Djermanovic)
7621f5d Update: add more specific linting messages to space-in-parens (#11121) (Che Fisher)

Bug Fixes

f826eab Fix: Allow line comment exception in object-curly-spacing (fixes #11902) (#12216) (Milos Djermanovic)
ae17d1c Fix: no-sequences is reporting incorrect locations (#12241) (Milos Djermanovic)
365331a Fix: object-shorthand providing invalid fixes for typescript (#12260) (Brad Zacher)
985c9e5 Fix: space-before-function-paren autofix removes comments (fixes #12259) (#12264) (Milos Djermanovic)
01da7d0 Fix: eqeqeq rule reports incorrect locations (#12265) (Milos Djermanovic)
a41fdc0 Fix: Remove autofixer for no-unsafe-negation (#12157) (Milos Djermanovic)
21eb904 Fix: basePath of OverrideTester (fixes #12032) (#12205) (Toru Nagashima)
2b1a13f Fix: no-extra-boolean-cast reports wrong negation node (fixes #11324) (#12197) (Milos Djermanovic)
e10eeba Fix: quotes autofix produces syntax error with octal escape sequences (#12118) (Milos Djermanovic)

Documentation

e915fff Docs: Improve examples and clarify default option (#12067) (Yuping Zuo)
520c922 Docs: Added naming convention details to plugin usage (#12202) (Henrique Barcelos)
319e4d8 Docs: adding finally example (#12256) (Jens Melgaard)
d52328f Docs: fix no-sequences with examples (#12239) (Milos Djermanovic)
a0a9746 Docs: Fix link in no-irregular-whitespace.md (#12196) (Timo Tijhof)

Indeed donates $10,000 to ESLint

2019-09-09T00:00:00Z

We are happy to share that Indeed has donated $10,000 to the ESLint project as part of their FOSS Contributor Fund. The FOSS Contributor Fund is a unique idea, where all Indeed employees may nominate an open source project to receive a one-time donation, and any employee who has contributed to an open source project during that month gets to vote on the nominees. We are honored to be one of the projects that Indeed employees chose to support.

“Most JavaScript projects directly or transitively depend on ESLint. An Indeed employee nominated ESLint to receive a donation from the FOSS Contributor Fund, and their colleagues clearly agreed. We’re happy to support the open source technologies that allow us to develop, protect, and maintain the digital infrastructure that supports our products and helps people get jobs.” – Duane O’Brien, Head of Open Source, Indeed

We are grateful to Duane for reaching out to discuss the details of their contribution, and to the employees at Indeed who voted to support ESLint. Donations such as this allow the all-volunteer ESLint team to continue to make project improvements going forward.

ESLint v6.3.0 released

2019-08-30T00:00:00Z

Highlights

eslint --init can automatically configure TypeScript support for ESLint in a new project.
The new reportUnusedDisableDirectives config option mirrors the existing --report-unused-disable-directives CLI flag.

Features

52e2cf5 New: reportUnusedDisableDirectives in config (refs eslint/rfcs#22) (#12151) (Toru Nagashima)
4c0b70b New: support TypeScript at config initializer (fixes #11789) (#12172) (Pig Fang)

Enhancements

020f952 Update: enforceForSequenceExpressions to no-extra-parens (fixes #11916) (#12142) (Milos Djermanovic)

Bug Fixes

aab1b84 Fix: reset to the default color (#12174) (Ricardo Gobbo de Souza)
4009d39 Fix: yoda rule produces invalid autofix with preceding yield (#12166) (Milos Djermanovic)
febb660 Fix: no-extra-boolean-cast invalid autofix with yield before negation (#12164) (Milos Djermanovic)
197f443 Fix: func-name-matching crash on descriptor-like arguments (#12100) (Milos Djermanovic)
644ce33 Fix: no-self-assign false positive with rest and spread in array (#12099) (Milos Djermanovic)
a81d263 Fix: fix message of function-paren-newline (#12136) (Pig Fang)

Documentation

00d2c5b Docs: corrected class extension example (#12176) (Marius M)
6abc7b7 Docs: Document the exception in no-unsafe-negation (#12161) (Milos Djermanovic)

Chores

0acdefb Chore: refactor code (#12113) (James George)
94e39d9 Chore: use GitHub Actions (#12144) (Toru Nagashima)
e88f305 Chore: support es2020 in fuzz (#12180) (薛定谔的猫)
31e5428 Chore: Fix wrong error object keys in test files (#12162) (Milos Djermanovic)
77f8ed1 Chore: update blogpost template (#12154) (Toru Nagashima)

ESLint v6.2.2 released

2019-08-23T00:00:00Z

Documentation

b809e72 Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

0e0b784 Upgrade: espree@^6.1.1 (#12158) (Kevin Partington)

ESLint v6.2.1 released

2019-08-20T00:00:00Z

This release includes a security fix in the eslint-utils package, which is a dependency of ESLint. The security issue affects users that run ESLint on untrusted source code (e.g. servers that lint the user’s project as a service). By taking advantage of a bug in a certain piece of analysis, a user could supply malicious source text that causes arbitrary code to be executed in the linting process.

This issue affects versions of eslint-utils between v1.2.0 and v1.4.0.
ESLint versions between v5.3.0 and v6.2.0 are potentially vulnerable (their allowed dependencies include vulnerable eslint-utils versions). However, these versions of ESLint can still be used safely if the eslint-utils dependency is updated to the latest version (e.g. by updating eslint-utils in a lockfile, or purging node_modules and reinstalling).
ESLint v6.2.1 is not vulnerable to the issue.

Documentation

4aeeeed Docs: update docs for ecmaVersion 2020 (#12120) (silverwind)
6886148 Docs: Add duplicate keys limitation to accessor-pairs (#12124) (Milos Djermanovic)

Dependency Upgrades

8c021b5 Upgrade: eslint-utils 1.4.2 (#12131) (Toru Nagashima)

ESLint v6.2.0 released

2019-08-18T00:00:00Z

Highlights

This release adds support for ES2020 syntax, which includes support for Dynamic Imports and BigInt. This can be enabled using ecmaVersion: 2020 in your configuration file.
A new rule, function-call-argument-newline, has been added.
Many bug fixes thanks to @mdjermanovic!

Features

afd8012 New: noInlineConfig setting (refs eslint/rfcs#22) (#12091) (Toru Nagashima)
8cd00b3 New: function-call-argument-newline (#12024) (finico)

Enhancements

fee6acb Update: support bigint and dynamic import (refs #11803) (#11983) (Toru Nagashima)
3d12378 Update: Fix accessor-pairs to enforce pairs per property in literals (#12062) (Milos Djermanovic)
2dc23b8 Update: fix no-dupe-keys false negatives on empty string names (#12069) (Milos Djermanovic)
d642150 Update: Check empty string property names in sort-keys (#12073) (Milos Djermanovic)
1aff8fc Update: warn about mixing ternary and logical operators (fixes #11704) (#12001) (Karthik Priyadarshan)
fbec99e Update: fix class-methods-use-this false negatives with exceptMethods (#12077) (Milos Djermanovic)
f5e0cc4 Update: Check computed method keys in no-extra-parens (#11973) (Milos Djermanovic)
5831767 Update: report location of func-names (fixes #12022) (#12028) (Pig Fang)

Bug Fixes

30ebf92 Fix: prefer-template autofix produces syntax error with octal escapes (#12085) (Milos Djermanovic)
13c3988 Fix: Check literal type explicitly in dot-notation (#12095) (Milos Djermanovic)
3e5ceca Fix: Handle empty string property names in getFunctionNameWithKind (#12104) (Milos Djermanovic)
9a043ff Fix: no-duplicate-case false positives on Object.prototype keys (#12107) (Milos Djermanovic)
4cb7877 Fix: fix no-extra-parens ignores some nodes (#11909) (Pig Fang)
19ab666 Fix: yoda exceptRange false positives on empty string property names (#12071) (Milos Djermanovic)
acce6de Fix: class-methods-use-this reports ‘undefined’ names (#12103) (Milos Djermanovic)
92ec2cb Fix: Allow bind call with a single spread element in no-extra-bind (#12088) (Milos Djermanovic)
bfdb0c9 Fix: no-extra-boolean-cast invalid autofix for Boolean() without args (#12076) (Milos Djermanovic)
cf31dab Fix: no-restricted-syntax - correct the schema (#12051) (Brad Zacher)

Documentation

01d38ce Docs: Remove TDZ scope from the scope manager interface documentation (#12054) (Milos Djermanovic)
11be2f8 Docs: do not recommend global-installed usage (#12016) (薛定谔的猫)
fb08b7c Docs: Remove readonly/writable global logic from no-undef (fixes #11963) (#12053) (Milos Djermanovic)
d961438 Docs: Fix Incorrect Documentation (#12045) (Michael Miceli)
d90183f Docs: add a case to func-names (#12038) (Chiawen Chen)
8a5b62d Docs: no use eslint.linter in code example (#12037) (薛定谔的猫)

Chores

fe631af Chore: minor typo fix (#12112) (James George)
34ccc0c Chore: Remove TDZ scope type condition from no-unused-vars (#12055) (Milos Djermanovic)

ESLint v6.1.0 released

2019-07-20T00:00:00Z

Enhancements

b974fcb Update: Check computed property keys in no-extra-parens (#11952) (Milos Djermanovic)
222d27c Update: Add for-in and for-of checks for props in no-param-reassign (#11941) (Milos Djermanovic)

Bug Fixes

d08683e Fix: glob processing (fixes #11940) (#11986) (Toru Nagashima)
bfcf8b2 Fix: dot-location errors with parenthesized objects (fixes #11868) (#11933) (Milos Djermanovic)
79e8d09 Fix: add parens for sequence expr in arrow-body-style (fixes #11917) (#11918) (Pig Fang)
e4c450f Fix: no-extra-parens autofix with in in a for-loop init (fixes #11706) (#11848) (Milos Djermanovic)
2dafe2d Fix: prefer-const produces invalid autofix (fixes #11699) (#11827) (Milos Djermanovic)
cb475fd Fix: Cache file error handling on read-only file system. (fixes #11945) (#11946) (Cuki)
6669f78 Fix: --init with Vue.js failed (fixes #11970) (#11985) (Toru Nagashima)
1fb3620 Fix: creating of enabledGlobals object without prototype (fixes #11929) (#11935) (finico)
19335b8 Fix: actual messageId and expected messageId are switched in rule tester (#11928) (Milos Djermanovic)

Documentation

105c098 Docs: update docs for object-curly-spacing (fixes #11634) (#12009) (Chiawen Chen)
89412c3 Docs: Fixed a typo (fixes #11999) (#12000) (Eddie Olson)
776dae7 Docs: fix wrong Node.js version in getting started (#11993) (Toru Nagashima)
4448261 Docs: some typos and optimization points (#11960) (Jason Lee)
c2f2db9 Docs: Replace global true and false with writable and readonly in rules (#11956) (Milos Djermanovic)
8b216e0 Docs: Fix incorrect example comments for unicode-bom rule (fixes #11937) (#11938) (Brandon Yeager)
e5f1ccc Docs: add ‘stricter rule config validating’ in migrating docs (#11905) (薛定谔的猫)

Dependency Upgrades

8f86cca Upgrade: eslint-scope@^5.0.0 (#12011) (Kevin Partington)
93633c2 Upgrade: Upgrade lodash dependency (fixes #11992) (#11994) (Cyd La Luz)
d8f2688 Upgrade: deps (#11904) (薛定谔的猫)

Chores

c90a12c Chore: update release script for new website repo (#12006) (Kai Cataldo)
2a10856 Chore: Add temporary test files to .gitignore (#11978) (Milos Djermanovic)
d83b233 Chore: update path for release bundles (#11977) (Kai Cataldo)
cc3885b Chore: add v8-compile-cache to speed up instantiation time (#11921) (薛定谔的猫)

ESLint v6.0.1 released

2019-06-24T00:00:00Z

Bug Fixes

b5bde06 Fix: --rulesdir option didn’t work (fixes #11888) (#11890) (Toru Nagashima)
13f0418 Fix: improve error message on --print-config (fixes #11874) (#11885) (Toru Nagashima)
056c2aa Fix: improve diagnostics for shareable-config-missing errors (#11880) (Teddy Katz)
d07f3fa Fix: CLIEngine#getRules() contains plugin rules (fixes #11871) (#11872) (Toru Nagashima)

Documentation

566b7aa Docs: Update no-confusing-arrow with the new default option (#11886) (Yuping Zuo)
21f4a80 Docs: Fix inconsistent linking in migration guide (#11881) (Teddy Katz)
f3a0774 Docs: Fix typo in 6.0.0 migration guide (#11870) (Kevin Partington)

ESLint v6.0.0 released

2019-06-21T00:00:00Z

Highlights

There are several breaking changes in 6.0.0. We’ve created a migration guide to explain the breaking changes and describe how to upgrade.
Configuration using glob patterns now supports extends and nested overrides
Using multiple processors is now supported.
The function-paren-newline rule has a new multiline-arguments option.
The sort-keys rule now supports a minKeys option.

Changes since v6.0.0-rc.0:

Bug Fixes

5f022bc Fix: no-else-return autofix produces name collisions (fixes #11069) (#11867) (Milos Djermanovic)
ded9548 Fix: multiline-comment-style incorrect message (#11864) (golopot)
c844c6f Fix: max-len properly ignore trailing comments (fixes #11838) (#11841) (ZYSzys)
1b5661a Fix: no-var should not fix variables named ‘let’ (fixes #11830) (#11832) (Milos Djermanovic)
81c3823 Fix: require-atomic-updates reports parameters (fixes #11723) (#11774) (Toru Nagashima)

Documentation

cad074d Docs: Add JSHint W047 compat to no-floating-decimal (#11861) (Timo Tijhof)
65faa04 Docs: Clarify prefer-destructuring array/object difference (fixes #9970) (#11851) (Oliver Sieweke)

Dependency Upgrades

81aa06b Upgrade: espree@6.0.0 (#11869) (Teddy Katz)
41f6304 Upgrade: sinon (#11855) (Toru Nagashima)
c57a4a4 Upgrade: @babel/polyfill => core-js v3 (#11833) (薛定谔的猫)

4d75956 Build: CI with Azure Pipelines (#11845) (Toru Nagashima)

Chores

167ce87 Chore: remove unuseable profile command (#11854) (Toru Nagashima)
1db3462 Chore: rm superfluous argument & fix perf-multifiles-targets (#11834) (薛定谔的猫)

ESLint v6.0.0-rc.0 released

2019-06-09T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

BigInt and dynamic import are at stage 4 (aside from some TC39 formalities), so we have begun to accept PRs to incorporate them into core ESLint rules. The valid-typeof rule now supports BigInt. Please see #11803 to track our progress in fully supporting these newly standardized language features.
The sort-keys rule now supports a minKeys option.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@6.0.0-rc.0 --save-dev

Migration Guide

Features

d662b17 New: Add classname attribute to JUnit testcase (refs #11068) (#11683) (Fabio Pitino)

Enhancements

f403b07 Update: introduce minKeys option to sort-keys rule (fixes #11624) (#11625) (Christian)
e4ab053 Update: support “bigint” in valid-typeof rule (#11802) (Colin Ihrig)
37e5193 Update: add endColumn to no-useless-escape (fixes #11629) (#11790) (Pig Fang)
9590587 Update: improve reported location of arrow-parens (fixes #11773) (#11775) (Pig Fang)

Bug Fixes

87451f4 Fix: no-octal should report NonOctalDecimalIntegerLiteral (fixes #11794) (#11805) (Milos Djermanovic)
21f3131 Fix: overrides handle relative paths as expected (fixes #11577) (#11799) (Toru Nagashima)
5509cdf Fix: fails the test case if autofix made syntax error (fixes #11615) (#11798) (Toru Nagashima)
cb1922b Fix: show custom message for namespace import (fixes #11580) (#11791) (Pig Fang)

Documentation

20908a3 Docs: removed ‘>’ prefix from from docs/working-with-rules (#11818) (Alok Takshak)

ad4b048 Build: Fix typo in blog post template (fixes #11614) (#11782) (Kai Cataldo)

Chores

e0fafc8 Chore: removes unnecessary assignment in loop (#11780) (Dimitri Mitropoulos)
8eaa9b2 Chore: remove incorrect comment (#11769) (薛定谔的猫)
4039a49 Chore: add .github/funding.yml (#11764) (Toru Nagashima)

ESLint v6.0.0-alpha.2 released

2019-05-25T00:00:00Z

Highlights

Configuration using glob patterns now supports extends and nested overrides
Using multiple processors is now supported

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@6.0.0-alpha.2 --save-dev

Migration Guide

If you’re upgrading from ESLint v5.x, we recommend looking at the migration guide, which describes the changes in great detail along with the steps you should take to address them. We expect that most users should be able to upgrade without any build changes, but the migration guide should be a useful resource if you encounter problems.

Breaking Changes

2d32a9e Breaking: stricter rule config validating (fixes #9505) (#11742) (薛定谔的猫)

Features

b5fa149 New: multiple processors support (fixes #11035, fixes #11725) (#11552) (Toru Nagashima)
54e6eda New: extends in glob-based config (fixes #8813) (#11554) (Toru Nagashima)

Enhancements

cf9cce8 Update: Add never option for new-parens (refs #10034) (#11379) (pfgithub)
71716eb Update: add fixer for no-div-regex rule (fixes #11355) (#11744) (joe-re)
53f7f4c Update: Uniform messages for the rules in “complexity” section (#11759) (Igor Novozhilov)

Bug Fixes

f9790ca Fix: typo: missing word in docs (#11750) (Dimitri Mitropoulos)
5dad0b1 Fix: Unignoring directories in .eslintignore (fixes #11684) (#11685) (Mykola Bilochub)
7c8e86b Fix: wrong ‘plugin-missing’ error on Node.js 12 (fixes #11720) (#11722) (Toru Nagashima)

Documentation

45bd336 Docs: add about RuleTester’s parser to migration guide (fixes #11728) (#11761) (Toru Nagashima)
1374be4 Docs: add table of contents in readme (#11765) (薛定谔的猫)
e45cc3f Docs: updated no-proto rule (fixes #11743) (#11746) (Francesco Trotta)
4625090 Docs: small fix about the migration guide (#11729) (Toru Nagashima)

Chores

9b87fee Chore: Fix formatter documentation generation (#11767) (Ilya Volodin)
f116208 Chore: Fix site generation script for releases (#11766) (Ilya Volodin)
0a801d7 Chore: improve perf test (#11756) (薛定谔的猫)
ec105b2 Chore: typo in JSDoc on timing.display’s return value (#11755) (Dimitri Mitropoulos)
15c6c63 Chore: eslint-config-eslint require node >= 8 (#11718) (薛定谔的猫)
219aecb Chore: restructure files (#11555) (Toru Nagashima)
67c671f Chore: ignore deprecated rules in fuzz tests (#11710) (Pig Fang)
af81cb3 Chore: make fuzzer produce minimal reproducible examples of bugs (#11700) (Teddy Katz)

ESLint v6.0.0-alpha.1 released

2019-05-10T00:00:00Z

Highlights

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide.

New breaking changes in this prerelease include:

Some config-loading bugs have been fixed. This change involved some refactoring to how config files are processed internally. Please let us know if you encounter any problems relating to configuration in this release.
eslint:recommended has been updated
no-redeclare has been made stricter

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@6.0.0-alpha.1 --save-dev

Migration Guide

Breaking Changes

6ae21a4 Breaking: fix config loading (fixes #11510, fixes #11559, fixes #11586) (#11546) (Toru Nagashima)
0fc8e62 Breaking: eslint:recommended changes (fixes #10768) (#11518) (薛定谔的猫)
20364cc Breaking: make no-redeclare stricter (fixes #11370, fixes #11405) (#11509) (Toru Nagashima)

Features

21dd211 New: add --resolve-plugins-relative-to flag (#11696) (Teddy Katz)

Bug Fixes

252efd3 Fix: delete unnecessary duplicated question (fixes #11617) (#11618) (HelloRusk)
1a3a88d Fix: Curly rule incorrectly flagging lexical declarations (fixes #11663) (#11675) (Brian Kurek)
f47d72c Fix: not set ecmaVersion to 6 when sourceType=module (fixes #9687) (#11649) (薛定谔的猫)
9484e9e Fix: ignore return statements in dead code (fixes #11647) (#11688) (Toru Nagashima)
aae6f65 Fix: don’t use deprecated API (#11689) (Toru Nagashima)
e4400b5 Fix: require-atomic-updates false positive (fixes #11194, fixes #11687) (#11224) (Toru Nagashima)
776b0fe Fix: update rule message of no-throw-literal (fixes #11637) (#11638) (Pig Fang)
67c08b6 Fix: consider comments in object-curly-spacing (fixes #11656) (#11657) (Pig Fang)
b6d41cb Fix: check token before using in no-cond-assign (fixes #11611) (#11619) (Pig Fang)
1dfe077 Fix: autofix of no-unneeded-ternary made syntax error (fixes #11579) (#11616) (Toru Nagashima)

Documentation

e84b6f8 Docs: fix example in object-curly-newline docs (#11633) (golopot)
483239e Docs: updated ImportDeclaration in docs-rules-indent (#11679) (Alok Takshak)
4b3b036 Docs: replace var with const in code examples (#11655) (Niyaz Akhmetov)
f2e7828 Docs: Fix Node 6 LTS EOL date (#11676) (James Ross)
adc6585 Docs: update status of breaking changes in migration guide (#11652) (Teddy Katz)
eef71e4 Docs: add missing items to migration guide (#11628) (Teddy Katz)
bebd079 Docs: fix grammar mistake in no-caller docs (#11623) (Daniel Lemay)

f62a451 Build: add node 12 (#11648) (薛定谔的猫)

Chores

f42d0af Chore: lazy loading for rules (#11705) (Toru Nagashima)
f5bae78 Chore: fix CLIEngine tests when os.tmpdir is a symlink (#11697) (Teddy Katz)
e4a08ba Chore: update eslint-plugin-node to 9.0.0 (#11670) (Toru Nagashima)
7f290a9 Chore: add eslint as a devDependeny (#11654) (Toru Nagashima)
139fd2f Chore: add markdownlint-cli (#11653) (Toru Nagashima)
8b4dba6 Chore: Add linting to git commit (#11556) (Nicholas C. Zakas)

Funding ESLint's Future: An Update

2019-05-01T00:00:00Z

Back in February, we announced the creation of the ESLint Collective to raise funds for the ongoing maintenance and development of ESLint. At the time, we were grateful to have both Facebook Open Source and Airbnb as our first two gold sponsors, each donating $1,000 per month.

In the past three months, we are happy to share that our monthly donations have reached over $7,000, 35% of the way towards our $20,000 goal. That’s an amazing achievement in such a short amount of time, and we are humbled that so many have reached out to support ESLint.

Introducing our latest sponsors

We are happy to share that the following sponsors have joined the ESLint Collective at the gold sponsor level, donating $1,000 or more per month:

GitKraken - $1,100
Badoo - $1,000
Salesforce - $1,000

The following sponsors have joined the ESLint Collective at the silver sponsor level, donating between $500 and $999 per month:

Amp Project - $500

And the following sponsors have joined the ESLint Collective at the bronze sponsor level, donating between $200 and $499 per month:

ESLint v6.0.0-alpha.0 released

2019-04-12T00:00:00Z

Highlights

Most of the highlights of this release are breaking changes, and are discussed further in the migration guide.

Non-breaking highlights:

The function-paren-newline rule has a new multiline-arguments option.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@6.0.0-alpha.0 --save-dev

Migration Guide

Breaking Changes

9e49b56 Breaking: upgrade espree to 6.0.0-alpha.0 (fixes #9687) (#11610) (Teddy Katz)
ef7801e Breaking: disallow invalid rule defaults in RuleTester (fixes #11473) (#11599) (Teddy Katz)
4e7cdca Breaking: comma-dangle enable functions: “never” (fixes #11502) (#11519) (薛定谔的猫)
12f256f Breaking: no-confusing-arrow enable allowParens: true (fixes #11503) (#11520) (薛定谔的猫)
25cc63d Breaking: simplify config/plugin/parser resolution (fixes #10125) (#11388) (Teddy Katz)
fd1c91b Breaking: throw an error for invalid global configs (refs #11338) (#11517) (Teddy Katz)
be83322 Breaking: Remove extra rules from eslint:recommended (fixes #10873) (#11357) (Kevin Partington)
2543f11 Breaking: remove deprecated experimentalObjectRestSpread option (#11420) (Teddy Katz)
0fb5fd4 Breaking: interpret rule options as unicode regexes (fixes #11423) (#11516) (Teddy Katz)
6e7da57 Breaking: drop Node.js 6 support (fixes #11456) (#11557) (Toru Nagashima)

Enhancements

5cfdc2d Update: Improve no-loop-func rule description and message (#11046) (Pedro Lopes)
2f8ae13 Update: support single argument on newline with function-paren-newline (#11406) (Vladlen Grachev)

Bug Fixes

0127d10 Fix: no-var fixed to incorrect code (fixes #11441) (#11443) (薛定谔的猫)
608a02c Fix: object-shorthand ignoreConstructors option (fixes #11595) (#11596) (overlookmotel)
b92ca6e Fix: getErrorResults function to not mutate passed parameter (#11592) (danielamaia)
19248e0 Fix: make overrides[].files matching dotfiles (fixes #11201) (#11225) (Toru Nagashima)

Documentation

8bfd1d1 Docs: add v6.0.0 migration guide (#11515) (Teddy Katz)
cbdee62 Docs: README updates to reflect JSCS compat project is finished (#11568) (Kevin Partington)
595de40 Docs: edit arrow-parens as-needed explanation (fixes #11202) (#11569) (Logan Lowder)
a73b4b8 Docs: Update README team and sponsors (ESLint Jenkins)

Dependency Upgrades

eeea893 Upgrade: update js-yaml package to 3.13.1 version (#11607) (Pobegaylo Maksim)
e70d5f7 Upgrade: compatible deps (#11608) (薛定谔的猫)
3396c3e Upgrade: karma@^4.0.1, drops Node 6 support, fixes vulnerability (#11570) (Kevin Partington)

Chores

3d9e137 Chore: fix test that fails when the CWD contains a space (#11612) (Teddy Katz)

ESLint v5.16.0 released

2019-03-29T00:00:00Z

Highlights

Formatters can now use rule metadata in their output! This enhancement was originally described and designed using our RFC process. More information can be found here.

A new built-in formatter, json-with-metadata, was created using this new feature. The json-with-metadata formatter is very similar to the json formatter, except that it also includes the rule metadata.

Enhancements

bc3e427 Update: pass rule meta to formatters RFC 10 (#11551) (Chris Meyer)

Bug Fixes

c06d38c Fix: Allow HTML formatter to handle no meta data (#11566) (Ilya Volodin)

Documentation

87a5c03 Docs: func-style: clarify when allowArrowFunctions is used (#11548) (Oliver Joseph Ash)
78358a8 Docs: fix duplicate punctuation in CLI docs (#11528) (Teddy Katz)

Dependency Upgrades

afe3d25 Upgrade: Bump js-yaml dependency to fix Denial of Service vulnerability (#11550) (Vernon de Goede)

dfef227 Build: gensite passes rulesMeta to formatter rendering (#11567) (Kevin Partington)

Chores

b452f27 Chore: Update README to pull in reviewer data (#11506) (Nicholas C. Zakas)
4fe7eb7 Chore: use nyc instead of istanbul (#11532) (Toru Nagashima)
f16af43 Chore: fix formatters/table test (#11534) (Toru Nagashima)

ESLint v5.15.3 released

2019-03-18T00:00:00Z

Bug Fixes

71adc66 Fix: avoid moving comments in implicit-arrow-linebreak (fixes #11521) (#11522) (Teddy Katz)

Chores

1f715a2 Chore: make test-case-property-ordering reasonable (#11511) (Toru Nagashima)

ESLint v5.15.2 released

2019-03-15T00:00:00Z

Bug Fixes

29dbca7 Fix: implicit-arrow-linebreak adds extra characters (fixes #11268) (#11407) (Mark de Dios)
a5dae7c Fix: Empty glob pattern incorrectly expands to “/**” (#11476) (Ben Chauvette)

Documentation

d6c1122 Docs: Add working groups to maintainer guide (#11400) (Nicholas C. Zakas)
956e883 Docs: Fix example in no-restricted-modules docs (#11454) (Paul O’Shannessy)
2c7431d Docs: fix json schema example dead link (#11498) (kazuya kawaguchi)
e7266c2 Docs: Fix invalid JSON in “Specifying Parser Options” (#11492) (Mihira Jayasekera)
0756128 Docs: Add visualstudio to formatter list (#11480) (Patrick Eriksson)
44de9d7 Docs: Fix typo in func-name-matching rule docs (#11484) (Iulian Onofrei)

Dependency Upgrades

5d2083f Upgrade: eslint-scope@4.0.3 (#11513) (Teddy Katz)

5fdb4d3 Build: compile deps to ES5 when generating browser file (fixes #11504) (#11505) (Teddy Katz)
06fa165 Build: update CI testing configuration (#11500) (Reece Dunham)
34a5382 Build: copy bundled espree to website directory (#11478) (Pig Fang)

Chores

448e8da Chore: improve crash reporting (fixes #11304) (#11463) (Alex Zherdev)
0f56dc6 Chore: make config validator params more consistent (#11435) (薛定谔的猫)
62fee4a Chore: eslint-config-eslint enable comma-dangle functions: “never” (#11434) (薛定谔的猫)
f078f9a Chore: use “file:” dependencies for internal rules/config (#11465) (Teddy Katz)

ESLint v5.15.1 released

2019-03-04T00:00:00Z

Bug Fixes

458053b Fix: avoid creating invalid regex in no-warning-comments (fixes #11471) (#11472) (Teddy Katz)

fe1a892 Build: bundle espree (fixes eslint/eslint.github.io#546) (#11467) (薛定谔的猫)

ESLint v5.15.0 released

2019-03-01T00:00:00Z

Highlights

The prefer-named-capture-group rule has been added. This rule encourages the use of named capture groups over numbered capture groups.

Features

ec59ec0 New: add rule “prefer-named-capture-group” (fixes #11381) (#11392) (Pig Fang)

Enhancements

de5cbc5 Update: remove invalid defaults from core rules (fixes #11415) (#11427) (Teddy Katz)

Bug Fixes

6489518 Fix: no-extra-parens crash when code is “((let))” (#11444) (Teddy Katz)

Documentation

8f3d717 Docs: Add non-attending TSC member info (#11411) (Nicholas C. Zakas)
ce0777d Docs: use more common spelling (#11417) (薛定谔的猫)

Dependency Upgrades

a44f750 Upgrade: eslint-scope@4.0.2 (#11461) (Teddy Katz)

4088c6c Build: Remove path.resolve in webpack build (#11462) (Kevin Partington)
eb0650b Build: fix linting errors on master (#11428) (Teddy Katz)
db0c5e2 Build: switch from browserify to webpack (fixes #11366) (#11398) (Pig Fang)

Chores

ee88475 Chore: add utils for rule tests (#11453) (薛定谔的猫)
5018378 Chore: enable require-unicode-regexp on ESLint codebase (#11422) (Teddy Katz)
f6ba633 Chore: lint all files in the repo at the same time (#11425) (Teddy Katz)
b9aabe3 Chore: run fuzzer along with unit tests (#11404) (Teddy Katz)

ESLint v5.14.1 released

2019-02-18T00:00:00Z

Bug Fixes

1d6e639 Fix: sort-keys throws Error at SpreadElement (fixes #11402) (#11403) (Krist Wongsuphasawat)

ESLint v5.14.0 released

2019-02-15T00:00:00Z

Highlights

For clarity configuration of global variables has been enhanced with two additional values readonly and writable. All previous values are still valid.
The prefer-destructuring rule is now auto-fixable.
Auto-fix was removed from prefer-spread to avoid creating invalid code.
--init CLI command has been updated to streamline available options.

Features

a23d197 New: add allowSingleLineBlocks opt. to padded-blocks rule (fixes #7145) (#11243) (richie3366)

Enhancements

51c4972 Update: Behavior of --init (fixes #11105) (#11332) (Nicholas C. Zakas)
550de1e Update: use default keyword in JSON schema (fixes #9929) (#11288) (Pig Fang)
983c520 Update: Use ‘readonly’ and ‘writable’ for globals (fixes #11359) (#11384) (Nicholas C. Zakas)
3c90dd7 Update: remove prefer-spread autofix (fixes #11330) (#11365) (薛定谔的猫)
5eb3121 Update: add fixer for prefer-destructuring (fixes #11151) (#11301) (golopot)
533d240 Update: no-shadow-restricted-names lets unassigned vars shadow undefined (#11341) (Teddy Katz)
d0e823a Update: Make --init run js config files through linter (fixes #9947) (#11337) (Brian Kurek)

Bug Fixes

85a04b3 Fix: adds conditional for separateRequires in one-var (fixes #10179) (#10980) (Scott Stern)
ab8ac6a Fix: Support boundary spread elements in sort-keys (#11158) (Jakub Rożek)
e25e7aa Fix: comma-spacing ignore comma before closing paren (fixes #11295) (#11374) (Pig Fang)
84ce72f Fix: Remove extraneous linefeeds in one-var fixer (fixes #10741) (#10955) (st-sloth)
92fc2f4 Fix: CircularJSON dependency warning (fixes #11052) (#11314) (Terry)

Documentation

104ae88 Docs: Update governance doc with reviewers status (#11399) (Nicholas C. Zakas)
a1f7c44 Docs: fix space-before-blocks correct code for “classes”: “never” (#11391) (PoziWorld)
14f58a2 Docs: fix grammar in object-curly-spacing docs (#11389) (PoziWorld)
d3e9a27 Docs: fix grammar in “those who says” (#11390) (PoziWorld)
ea8e804 Docs: Add note about support for object spread (fixes #11136) (#11395) (Steven Thomas)
95aa3fd Docs: Update README team and sponsors (ESLint Jenkins)
ad7a380 Docs: Update README team and sponsors (ESLint Jenkins)
3e0c417 Docs: Fix grammar in “there’s nothing prevent you” (#11385) (PoziWorld)
de988bc Docs: Fix grammar: Spacing improve -> Spacing improves (#11386) (PoziWorld)
1e56897 Docs: “the function actually use”: use -> uses (#11380) (PoziWorld)
5a71bc9 Docs: Update README team and sponsors (ESLint Jenkins)
82a58ce Docs: Update README team and sponsors (ESLint Jenkins)
546d355 Docs: Update README with latest sponsors/team data (#11378) (Nicholas C. Zakas)
c0df9fe Docs: ... is not an operator (#11232) (Felix Kling)
7ecfdef Docs: update typescript parser (refs #11368) (#11369) (薛定谔的猫)
173eb38 Docs: Clarify ecmaVersion doesn’t imply globals (refs #9812) (#11364) (Keith Maxwell)
389362a Docs: clarify motivation for no-prototype-builtins (#11356) (Teddy Katz)
4dd19a3 Docs: mention ‘prefer-spread’ in docs of ‘no-useless-call’ (#11348) (Klaus Meinhardt)
4fd83d5 Docs: fix a misleading example in one-var (#11350) (薛定谔的猫)

Dependency Upgrades

0c02932 Upgrade: espree@5.0.1 (#11401) (Ilya Volodin)
f1d3a7e Upgrade: some deps (fixes #11372) (#11373) (薛定谔的猫)

Chores

9441ce7 Chore: update incorrect tests to fix build failing (#11354) (薛定谔的猫)

Funding ESLint's Future

2019-02-12T00:00:00Z

June 2019 will mark six years since ESLint was first released. What began as a side project for a very narrow use case has grown into the most popular JavaScript linter in the world, with over 6.5 million npm downloads every week. ESLint is now used by both large companies and individual developers to help find and fix problems with JavaScript code every day. In addition, ESLint has been flexible enough to work with languages derived from JavaScript, such as Flow and TypeScript, and even helps mobile developers by linting React Native.

All of this means that ESLint has become an important part of the JavaScript ecosystem. It’s a tool that the JavaScript community depends on and expects to be available, performant, and secure. These expectations are currently being met by an all-volunteer team who spends their free time during lunch breaks, nights, and weekends maintaining ESLint. And while that has worked well for normal maintenance, it’s grown difficult to deal with more involved issues such as roadmap planning and security issues.

In short, we’ve realized that in order for ESLint to continue to grow and evolve, we need to get more organized and set up a way to fund ESLint’s development going forward.

The ESLint Collective

Today, we are happy to announce the ESLint Collective on Open Collective. Open Collective is a secure way for people to sustain and support open source projects. The funds taken in and paid out are publicly available on each collective’s page, so there is 100% transparency around the money a collective uses. Open Collective has already helped other JavaScript ecosystem projects such as Webpack and Babel to fund their ongoing development, and the ESLint team is happy to join them on what has proven to be a great option for open source sustainability.

Some of the benefits of working with Open Collective include:

Full Transparency. Everyone gets to see where money is coming from and where it’s going.
Individual and Corporate Sponsors. Open Collective makes it easy for both individuals and companies to sponsor open source projects.
Potential Tax Benefits. Because funds are paid to the Open Source Collective, a 501©(6) organization in the U.S., there may be tax benefits for some donors (please check with your accountant).
Automatic Invoicing. For corporate sponsors, Open Collective automatically generates and sends invoices for tracking purposes.
Open Participation. Anyone can request reimbursement for funds spent helping the ESLint project and ESLint can pay out to anyone.

How will the money be spent?

The ESLint team has a lot of ideas about how to proceed going forward. Depending on the amount we raise, here are some of the things we’re planning:

Paying team members for maintenance and development. All ESLint team members are still contributing in their spare time. Having the option to work part-time or full-time on ESLint, and be compensated for it, would allow for faster and more consistent development.
Rewarding contributions from the community. We’d like to reward everyone who contributes to ESLint, whether it’s a one-time contribution or ongoing contributions. We are still figuring out the details, but rewarding people with everything from stickers and t-shirts to cash payouts for significant contributions are things we are thinking about right now.
Improve documentation. ESLint’s documentation hasn’t had a significant overhaul since the project was first released. We feel there are a lot of ways to improve the documentation, including potentially contracting an information architect or technical writer to improve our documentation.
Better communication and support. By paying team members part-time or full-time, that also opens up the possibility of sending team members to meetups, companies, and conferences to interact with the community and better understand the problems developers are facing.
Developing a Roadmap. For a while, the ESLint team has mostly worked on a one-off basis in terms of which features to implement. Without knowing who would be able to spend what amount of time on the project, it was difficult to do long-term planning and develop a roadmap for the future. This is something we will finally be able to do when we are a self-sustaining project.

Our Goal: $20,000 per month

In order to achieve everything we have in mind, we believe that we will need $20,000 per month. With this amount, we can sustain ESLint for the foreseeable future.

Introducing our first sponsors

We’re also excited to announce our first sponsors. Facebook and Airbnb have both pledged $1,000 per month to support ESLint.

Additionally, Frontend Masters has donated $200 to support ESLint.

We’d like to thank Eric Nakagawa at Facebook, Jordan Harband at Airbnb, Marc Grabanski at Frontend Masters, and Pia Mancini at Open Collective for supporting our early sponsorship efforts at their respective companies.

The best is yet to come for ESLint

We are grateful to the ESLint community for your continued support and feedback, and we’re looking forward to continuing to interact and grow with you. We truly believe that the best is yet to come for ESLint, and with financial support from the companies that use ESLint, we will be able to achieve our vision.

ESLint v5.13.0 released

2019-02-01T00:00:00Z

Highlights

Configuration of globals has been improved with three new options: “off”, “readable”, and “writeable”.

“off”: Completely disables a global variable that was previously defined.
“readable”: Equivalent to the old false value, “readable” global variables are in scope but cannot be written to.
“writeable”: Equivalent to the old true value, “writeable” global variables can be read from and written to.

Configurations using the old true/false values will continue to work, but we encourage you to use the newer, more explicit options.

Check out the documentation on specifying globals for more details!

Features

0a3c3ff New: Allow globals to be disabled/configured with strings (fixes #9940) (#11338) (Teddy Katz)

Enhancements

b5143bf Update: for-direction detection false positives/negatives (#11254) (Ruben Bridgewater)

Bug Fixes

5b14ad1 Fix: false positive in no-constant-condition (fixes #11306) (#11308) (Pig Fang)
6567c4f Fix: only remove arrow before body in object-shorthand (fixes #11305) (#11307) (Pig Fang)

Documentation

fa2f370 Docs: update rule configuration values in examples (#11323) (Kai Cataldo)
c464e27 Docs: Rename result -> foo (#11210) (Alexis Tyler)

Chores

91c8884 Chore: use local function to append “s” instead of a package (#11293) (Timo Tijhof)
9005e63 Chore: increase camelcase test coverage (#11299) (Redmond Tran)
dccee63 Chore: avoid hard-coding the list of core rules in eslint:recommended (#11336) (Teddy Katz)
c1fd6f5 Chore: remove undocumented Linter#rules property (refs #9161) (#11335) (Teddy Katz)
36e3356 Chore: remove dead code for loading rules (#11334) (Teddy Katz)

The future of TypeScript on ESLint

2019-01-18T00:00:00Z

A couple of weeks ago, the TypeScript team shared their roadmap in which they described formally adopting ESLint in their repo and working to improve TypeScript compatibility for ESLint:

Linting

Semantic rules in ESLint

Parity with TSLint

Speed & scalability

Editor integration for ESLint

In a survey we ran in VS Code a few months back, the most frequent theme we heard from users was that the linting experience left much to be desired. Since part of our team is dedicated to editing experiences in JavaScript, our editor team set out to add support for both TSLint and ESLint. However, we noticed that there were a few architectural issues with the way TSLint rules operate that impacted performance. Fixing TSLint to operate more efficiently would require a different API which would break existing rules (unless an interop API was built like what wotan provides).

Meanwhile, ESLint already has the more-performant architecture we’re looking for from a linter. Additionally, different communities of users often have lint rules (e.g. rules for React Hooks or Vue) that are built for ESLint, but not TSLint.

Given this, our editor team will be focusing on leveraging ESLint rather than duplicating work. For scenarios that ESLint currently doesn’t cover (e.g. semantic linting or program-wide linting), we’ll be working on sending contributions to bring ESLint’s TypeScript support to parity with TSLint. As an initial testbed of how this works in practice, we’ll be switching the TypeScript repository over to using ESLint, and sending any new rules upstream.

We, just like a lot of the JavaScript and TypeScript communities, were very excited about this announcement. Several members of the ESLint team have been working on improving TypeScript compatibility over the past couple of years, including James Henry, Kai Cataldo, Kevin Partington, Toru Nagashima, and Nicholas Zakas. That work focused mainly on the TypeScript parser, typescript-eslint-parser (and partly on eslint-plugin-typescript, which was not maintained by the ESLint team but had been maintained by Nicholas and James until recently). The Typescript parser would undoubtedly become the centerpiece of the TypeScript-in-ESLint story going forward; as such, we wanted to make sure that it would be properly maintained.

Announcing the `typescript-eslint` project

James Henry, who has long been the driving force behind TypeScript compatibility for ESLint, has started the typescript-eslint project as a centralized repository for all things related to TypeScript ESLint compatibility. This will be the new home of the TypeScript parser, eslint-plugin-typescript, and any other utilities that will make the TypeScript ESLint experience as seamless as possible.

While the ESLint team won’t be formally involved in the new project, we are fully supportive of James’ efforts and will be keeping lines of communication open to ensure the best ESLint experience for TypeScript developers.

What this means going forward

The ESLint team will no longer be maintaining typescript-eslint-parser
- The repository will be archived as of today
- There will be no further releases of typescript-eslint-parser on npm
Anyone using typescript-eslint-parser should use @typescript-eslint/parser instead
Those interested in how TypeScript support is coming along should follow the typescript-eslint repository

Once again, we are very excited to welcome the TypeScript community into the ESLint community and look forward to seeing how James and the typescript-eslint team make ESLint the best choice for linting TypeScript code.

ESLint v5.12.1 released

2019-01-18T00:00:00Z

Bug Fixes

aa56247 Fix: avoid loading core rules dynamically from FS in Linter (#11278) (Peter Metz)
c403445 Fix: warn constant on RHS of || in no-constant-condition (fixes #11181) (#11253) (Merlin Mason)
9194f45 Fix: Manage severity of 1 with TAP reporter (fixes #11110) (#11221) (Gabriel Cousin)

Documentation

04450bb Docs: clarify process for adding committers (#11272) (Kai Cataldo)
3ffcf26 Docs: add @g-plane as committer (#11277) (Kai Cataldo)
000f495 Docs: fix example for sort-imports ignoreDeclarationSort (#11242) (Remco Haszing)
7c0bf2c Docs: Add npx usage to Getting Started guide (#11249) (eyal0803)
da9174e Docs: fixes typo peerDepencies (#11252) (Christian Kühl)
9c31625 Docs: Improve custom formatter docs (#11258) (Nicholas C. Zakas)

Chores

eb5c401 Chore: use meta.messages in some rules (2/4) (refs #9870) (#10773) (薛定谔的猫)

ESLint v5.12.0 released

2019-01-04T00:00:00Z

Highlights

The sort-imports rule has a new ignoreDeclarationSort option.

Enhancements

0d91e7d Update: Add sort-imports ignoreDeclarationSort (fixes #11019) (#11040) (Remco Haszing)

Bug Fixes

bfff77a Fix: no-param-reassign parameter in ternary operator (fixes #11236) (#11239) (周昊宇)

Dependency Upgrades

166853d Upgrade: eslint-plugin-eslint-plugin@2.0.1 (#11220) (薛定谔的猫)
258b654 Upgrade: require-uncached renamed to import-fresh (#11066) (薛定谔的猫)

f92d6f0 Build: Add karma-chrome-launcher support (#11027) (薛定谔的猫)

ESLint v5.11.1 released

2018-12-26T00:00:00Z

Bug Fixes

de79f10 Fix: handle optional catch bindings in no-useless-catch (#11205) (Colin Ihrig)

ESLint v5.11.0 released

2018-12-22T00:00:00Z

Highlights

One new rule has been added: no-useless-catch
The indent rule now supports a VariableDeclarator: "first" option.

Features

b4395f6 New: add option first for VariableDeclarator in indent (fixes #8976) (#11193) (Pig Fang)
2b5a602 New: no-useless-catch rule (fixes #11174) (#11198) (Alexander Grasley)

Enhancements

4242314 Update: handle computed properties in camelcase (fixes #11084) (#11113) (Bence Dányi)

Bug Fixes

06b3b5b Fix: Account for comments in implicit-arrow-linebreak (#10545) (Mark de Dios)

Documentation

1009304 Docs: add a note for no-unused-expressions (fixes #11169) (#11192) (Pig Fang)
88f99d3 Docs: clarify how to use configs in plugins (#11199) (Kai Cataldo)
bcf558b Docs: Clarify the no-unused-vars docs (#11195) (Jed Fox)
a470eb7 Docs: Fix no-irregular-whitespace description (#11196) (Jed Fox)
8abc8af Docs: Remove a misleading example (#11204) (Bogdan Gradinariu)
733d936 Docs: link to JSDoc EOL blogpost in valid-jsdoc and require-jsdoc (#11191) (Nathan Diddle)
d5eb108 Docs: Ensure triage label is added to new issues (#11182) (Teddy Katz)
617a287 Docs: add missing deprecation notices for jsdoc rules (#11171) (Teddy Katz)

ESLint v5.10.0 released

2018-12-08T00:00:00Z

Highlights

The padding-line-between-statements rule has new statement types: multiline-const, multiline-let, multiline-var, singleline-const, singleline-let, and singleline-var.
The require-jsdoc and valid-jsdoc rules have been deprecated, following our previously announced decision to end support for JSDoc in ESLint.

Enhancements

4b0f517 Update: single- and multiline const, let, var statements (fixes #10721) (#10919) (Tom Panier)
9666aba Update: space-infix-ops reports violating operator (#10934) (Bence Dányi)
4490d7a Update: deprecate valid-jsdoc and require-jsdoc (#11145) (Teddy Katz)
62fd2b9 Update: Amend keyword-spacing to validate default keywords (#11097) (Bin Ury)
3025cdd Update: don’t indent leading semi in line after import (fixes #11082) (#11085) (Pig Fang)

Bug Fixes

c14f717 Fix: Update all-files-ignored.txt message to be less confusing (#11075) (z.ky)
3bf0332 Fix: fix the fixer of lone comma with comments (fixes #10632) (#11154) (Pig Fang)
c0a80d0 Fix: Do not strip underscores in camelcase allow (fixes #11000) (#11001) (Luke Page)
54dfa60 Fix: Typo in function comment parameters (#11111) (Pierre Maoui)

Documentation

9f3573d Docs: Clarify the CLIEngine options (#10995) (Ed Morley)
60dfb6c Docs: Update issue templates (#11163) (Teddy Katz)
958987a Docs: Fix link to rule no-useless-rename (#11165) (Brian)
c6471ed Docs: fix typo in issue-templates/new-rule (#11149) (薛定谔的猫)
a675c89 Docs: (Grammar) “the setup” -> “to set up” (#11117) (MarvinJWendt)
cf296bd Docs: switch incorrect example with correct one (#11107) (Romain Le Quellec)
d2d500c Docs: no-console#When-Not-To-Use provides incorrect rule snippet (#11093) (Lawrence Chou)

Dependency Upgrades

f850726 Upgrade: Espree v5.0.0 (#11161) (Kai Cataldo)
5da378a Upgrade: eslint-release@1.2.0 (#11073) (Teddy Katz)

709190f Build: fix test failure on Node 11 (#11100) (Teddy Katz)

Chores

dd7b0cb Chore: refactor template literal feature detection in ‘quotes’ rule (#11125) (Bryan)
4bcdfd0 Chore: fix some jsdoc-related issues (#11148) (薛定谔的猫)
5d451c5 Chore: Remove dependency on is-resolvable (#11128) (Matt Grande)
bc50dc7 Chore: Move ignored-paths, report-translator to lib/util (refs #10559) (#11116) (Kevin Partington)
f394a1d Chore: Extract config comment parsing (#11091) (Nicholas C. Zakas)
e18c827 Chore: refactor linter#parseBooleanConfig to improve readability (#11074) (薛定谔的猫)

End-of-Life for Built-in JSDoc Support in ESLint

2018-11-27T00:00:00Z

Over the past few years, the ESLint project has grown in size and scope. What originally consisted of a single executable package has grown into a project with multiple packages including several parsers and other utilities. Although the project has grown, the size of the team has not, and as such we’ve had to make some tough decisions about how to continue maintaining the ESLint project as a whole using an all-volunteer team.

Current JSDoc Support in ESLint

JSDoc support in ESLint currently consists of:

Maintaining the Doctrine JSDoc comment parser
The require-jsdoc rule
The valid-jsdoc rule
The SourceCode#getJSDocComment() method

To support JSDoc in ESLint, we had been spending an outsized amount of time maintaining Doctrine and the valid-jsdoc rule as compared to the effort required to maintain the rest of the project. Those two parts, in addition to the require-jsdoc rule and SourceCode#getJSDocComment() are being end-of-lifed beginning today.

What End-of-Life Means

End-of-life for core JSDoc support means you will see the following happening in the next several weeks:

Doctrine will no longer be updated. Version 3.0.0, published two weeks ago, will be the last major version release. We may need to do a couple of small updates before stopping all maintenance, but we will no longer be adding features or fixing bugs. We believe Doctrine is in a solid and reliable state and would make a good base if anyone wants to fork it to begin a new project.
The require-jsdoc and valid-jsdoc rules will be deprecated. These two rules will remain in ESLint but we will no longer add new features or fix bugs for them. These rules may be removed in a future major release of ESLint.
The SourceCode#getJSDocComment() method will be deprecated. We won’t be making changes related to this method and will remove it in a future major release of ESLint.

Be sure to check the release announcements for when these changes take effect.

Suggested Replacement

If you would like to continue checking JSDoc comments using ESLint, we suggest using the community-supported eslint-plugin-jsdoc plugin. This plugin contains several rules that are more specific than the core ESLint rules being deprecated and may actually be a better fit for most projects.

Frequently Asked Questions

Why aren’t you trying to find new maintainers for Doctrine?

There are a couple of reasons why we decided not to find new maintainers for Doctrine.

First, while the package is widely-used, there has been very few contributions from those outside of the team. Whereas some packages get a lot of attention from outside contributors and it may be easy to find a new maintainer, that wasn’t the case with Doctrine.

Second, because Doctrine is a part of the JS Foundation, taking over its maintenance means being involved with the Foundation. In the event that a single maintainer decided to take this on, that might be too much overhead.

With nearly 7 million weekly downloads on npm, it seemed like the best option for existing users was to end-of-life the Doctrine project rather than try to find a new maintainer. We believe a better option for an interested new maintainer would be to fork Doctrine and start fresh rather than try to take over the way Doctrine had already been maintained.

Why are you going to keep the JSDoc rules and not maintain them?

We are keeping the existing JSDoc rules to give users plenty of time to transition to using eslint-plugin-jsdoc. We try to minimize the number of times we ask our users to update their config files, and by deprecated the existing JSDoc rules while keeping them available, we are allowing everyone to make a gradual transition while also freeing up ESLint team resources to work on other parts of the project.

What if I have other questions about this?

Open a discussion or stop by our Discord server.

ESLint v5.9.0 released

2018-11-09T00:00:00Z

Highlights

The following are the most important changes in this release.

The --fix-type option

This version introduces a new --fix-type option for the command line interface. This option allows you to filter the type of fixes applied when using --fix. You can specify the type of fixes to apply based on the new rule types we’ve assigned to each rule. The three rule types are:

problem - the rule flags a potential problem with your code.
suggestion - the rule flags something that could be done in a better or preferred way.
layout - the rule flags changes limited to whitespace, semicolons, commas, or parentheses.

You might find this option useful if you’re using a source code formatter with ESLint, in which case you might want to use --fix-type problem,suggestion to only apply fixes for rules that won’t clash with your formatter.

There is also a new fixTypes option that can be passed to the CLIEngine class that implements the same feature for those using the API.

Note: Fixes in custom rules will not be applied when using --fix-type unless they include a meta.type field. If you are maintaining a plugin with custom rules, please update your rules.

Features

7ad86de New: Add --fix-type option to CLI (fixes #10855) (#10912) (Nicholas C. Zakas)

Enhancements

c832cd5 Update: add ignoreDestructuring option to id-match rule (#10554) (一名宅。)
ae2b61d Update: “off” options for “space-before-blocks” (refs #10906) (#10907) (Sophie Kirschner)
79a2797 Update: no-restricted-imports to check re-export (fixes #9678) (#11064) (Nicholas C. Zakas)
802e926 Update: Warn for deprecation in Node output (fixes #7443) (#10953) (Colin Chang)

Bug Fixes

9436712 Fix: Unused recursive function expressions (fixes #10982) (#11032) (Sergei Startsev)
54687a8 Fix: prefer-const autofix multiline assignment (fixes #10582) (#10987) (Scott Stern)
dcc6233 Fix: Ignore empty statements in no-unreachable (fixes #9081) (#11058) (Nicholas C. Zakas)
5525eb6 Fix: rule deprecation warnings did not consider all rules (#11044) (Teddy Katz)

Documentation

57f357e Docs: Update require-await docs with exception (fixes #9540) (#11063) (Nicholas C. Zakas)
3dd7493 Docs: update ecmaVersion to include 2019/10 values (#11059) (Vse Mozhet Byt)
4fe3287 Docs: Cross-reference two rules (refs #11041) (#11042) (Paul Melnikow)
44d37ca Docs: Update steps for adding new TSC member (#11038) (Nicholas C. Zakas)

Dependency Upgrades

607635d Upgrade: eslint-plugin-node & eslint-plugin (#11067) (薛定谔的猫)

Chores

0800b20 Chore: fix invalid super() calls in tests (#11054) (Teddy Katz)

ESLint v5.8.0 released

2018-10-26T00:00:00Z

Highlights

The Linter API now has a static version property, for consistency with the CLIEngine.version property. (Previously, the version property was only present on instances of Linter rather than Linter itself.)

Enhancements

3943635 Update: Create Linter.version API (fixes #9271) (#11010) (Nicholas C. Zakas)

Bug Fixes

9152417 Fix: deprecation warning in RuleTester using Node v11 (#11009) (Teddy Katz)
57ef0fd Fix: prefer-const when using destructuring assign (fixes #8308) (#10924) (Nicholas C. Zakas)

Documentation

e349a03 Docs: Update issue templates to ask for PRs (#11012) (Nicholas C. Zakas)
a940cf4 Docs: Mention version for config glob patterns (fixes #8793) (Nicholas C. Zakas)
58ff359 Docs: add instructions for npm 2FA (refs #10631) (#10992) (Teddy Katz)

Dependency Upgrades

2f87bb3 Upgrade: eslint-release@1.0.0 (refs #10631) (#10991) (Teddy Katz)

5a31a92 Build: compile espree’s deps to ES5 when generating site (fixes #11014) (#11015) (Teddy Katz)
6e1c530 Build: run tests on Node 11 (#11008) (Teddy Katz)

Chores

3d88b38 Chore: avoid using legacy report API in no-irregular-whitespace (#11013) (Teddy Katz)
577cbf1 Chore: Add typescript-specific edge case tests to space-infix-ops (#10986) (Bence Dányi)
d45b184 Chore: Using deconstruction assignment for shelljs (#10974) (ZYSzys)

ESLint v5.7.0 released

2018-10-12T00:00:00Z

Highlights

Three rules gained new options in this release:

padding-line-between-statements has a new iife node type to specifically target immediately-invoked function expression invocations as distinct statements.
no-tabs has a new allowIndentationTabs option to permit tabs only for indentation and nowhere else.
camelcase has a new allow option that can be configured to individually allow certain non-camelcase identifiers like React’s UNSAFE_componentWillMount.

Enhancements

6cb63fd Update: Add iife to padding-line-between-statements (fixes #10853) (#10916) (Kevin Partington)
5fd1bda Update: no-tabs allowIndentationTabs option (fixes #10256) (#10925) (Kevin Partington)
066f7e0 Update: camelcase rule ignoreList added (#10783) (Julien Martin)

Bug Fixes

d12be69 Fix: no-extra-bind No autofix if arg may have side effect (fixes #10846) (#10918) (Kevin Partington)
847372f Fix: no-unused-vars false pos. with markVariableAsUsed (fixes #10952) (#10954) (Roy Sutton)
543edfa Fix: Fix error with one-var (fixes #10937) (#10938) (Justin Krup)
5fe0e1a Fix: no-invalid-regexp disallows \ at end of pattern (fixes #10861) (#10920) (Toru Nagashima)

Documentation

95c4cb1 Docs: Fix typo for no-unsafe-finally (#10945) (Sergio Santoro)
f85547a Docs: Add ‘When Not To Use’ section to space-infix-ops (#10931) (Bence Dányi)
3dccac4 Docs: Update working-with-parsers link (#10929) (Azeem Bande-Ali)
557a8bb Docs: Remove old note about caching, add a new one (fixes #10739) (#10913) (Zac)

Dependency Upgrades

70bde69 Upgrade: table to version 5 (#10903) (Rouven Weßling)

Chores

4132de7 Chore: Simplify space-infix-ops (#10935) (Bence Dányi)
fe8111a Chore: Add more test cases to space-infix-ops (#10936) (Bence Dányi)
2e52bca Chore: Update issue templates (#10900) (Nicholas C. Zakas)

ESLint v5.6.1 released

2018-09-28T00:00:00Z

Bug Fixes

9b26bdb Fix: avoid exponential require-atomic-updates traversal (fixes #10893) (#10894) (Teddy Katz)
9432b10 Fix: make separateRequires work in consecutive mode (fixes #10784) (#10886) (Pig Fang)
9d52541 Fix: Remove duplicate error message on crash (fixes #8964) (#10865) (Nicholas C. Zakas)

Documentation

d3f3994 Docs: add information about reporting security issues (#10889) (Teddy Katz)
a6ebfd3 Docs: clarify defaultAssignment option, fix no-unneeded-ternary examples (#10874) (CoffeeTableEspresso)
4eb9a49 Docs: Update quotes.md (#10862) (The Jared Wilcurt)
9159e9b Docs: Update complexity.md (#10867) (Szymon Przybylski)
14f4e46 Docs: Use Linter instead of linter in Nodejs API page (#10864) (Nicholas C. Zakas)

Dependency Upgrades

e51868d Upgrade: debug@4 (fixes #10854) (#10887) (薛定谔的猫)

cc458f4 Build: fix failing tests on master (#10890) (Teddy Katz)

Chores

b3e3cb1 Chore: Update debug log name to match filename (#10863) (Nicholas C. Zakas)

ESLint v5.6.0 released

2018-09-14T00:00:00Z

Enhancements

c5b688e Update: Added generators option to func-names (fixes #9511) (#10697) (Oscar Barrett)

Bug Fixes

7da36d5 Fix: respect generator function expressions in no-constant-condition (#10827) (Julian Rosse)

Chores

0a65844 Chore: quote enable avoidEscape option in eslint-config-eslint (#10626) (薛定谔的猫)
32f41bd Chore: Add configuration wrapper markdown for the bug report template (#10669) (Iulian Onofrei)

ESLint v5.5.0 released

2018-08-31T00:00:00Z

Enhancements

b61d2cd Update: max-params to only highlight function header (#10815) (Ian Obermiller)

Bug Fixes

6e110e6 Fix: camelcase duplicate warning bug (fixes #10801) (#10802) (Julian Rosse)

Documentation

5103ee7 Docs: Add Brackets integration (#10813) (Jan Pilzer)
2824d43 Docs: fix comment placement in a code example (#10799) (Vse Mozhet Byt)
80c8598 Docs: gitignore syntax updates (fixes #8139) (#10776) (Gustavo Santana)

Dependency Upgrades

2b2f11d Upgrade: babel-code-frame to version 7 (#10808) (Rouven Weßling)
10690b7 Upgrade: devdeps and deps to latest (#10622) (薛定谔的猫)

Chores

cb946af Chore: use meta.messages in some rules (1/4) (#10764) (薛定谔的猫)

ESLint v5.4.0 released

2018-08-17T00:00:00Z

Enhancements

f3d8454 Update: Improve no-extra-parens error message (#10748) (Timo Tijhof)

Bug Fixes

034690f Fix: no-invalid-meta crashes for non Object values (fixes #10750) (#10753) (Sandeep Kumar Ranka)
562a03f Fix: consistent-docs-url crashes if meta.docs is empty (fixes #10722) (#10749) (Sandeep Kumar Ranka)

Documentation

a70909f Docs: Add jscs-dev.github.io links (#10771) (Gustavo Santana)
11a462d Docs: Broken jscs.info URLs (fixes #10732) (#10770) (Gustavo Santana)

Chores

985567d Chore: rm unused dep string.prototype.matchall (#10756) (薛定谔的猫)
6492233 Chore: enable no-prototype-builtins in codebase (fixes #10660) (#10664) (薛定谔的猫)
137140f Chore: use eslintrc overrides (#10677) (薛定谔的猫)

ESLint v5.3.0 released

2018-08-03T00:00:00Z

Highlights

Four new rules have been added:

no-misleading-character-class reports multi-code-point characters in regular expression character classes. Using these characters in character classes often results in surprising behavior.
require-atomic-updates reports potential race conditions that result from updating values in async or generator functions.
no-async-promise-executor reports uses of the Promise constructor that have an async function as the argument. Using an async function in this scenario is not necessary and a potential source of bugs.
require-unicode-regexp requires all regular expressions to have the u flag. Regular expressions with the u flag have stricter parsing rules and handle unicode text more sensibly, which is useful to avoid unexpected behavior when writing regular expressions.

Features

6eb972c New: require-unicode-regexp rule (fixes #9961) (#10698) (Toru Nagashima)
2cc3240 New: add no-misleading-character-class (fixes #10049) (#10511) (Toru Nagashima)
9e93d46 New: add no-async-promise-executor rule (fixes #10217) (#10661) (Teddy Katz)
5a2538c New: require-atomic-updates rule (fixes #10405) (#10655) (Teddy Katz)

Enhancements

e37a593 Update: Fix incorrect default value for position (#10670) (Iulian Onofrei)
f026fe1 Update: Fix ‘function’ in padding-line-between-statements (fixes #10487) (#10676) (Kevin Partington)
9e76be7 Update: indent comments w/ nearby code if no blank lines (fixes #9733) (#10640) (Kevin Partington)

Bug Fixes

5c5d64d Fix: ignored-paths for Windows path (fixes #10687) (#10691) (Toru Nagashima)
d56c39d Fix: ESLint cache no longer stops autofix (fixes #10679) (#10694) (Kevin Partington)
877f4b8 Fix: The “…/…” folder is always ignored (fixes #10675) (#10682) (Sridhar)
8b83d2b Fix: always resolve default ignore patterns from CWD (fixes #9227) (#10638) (Teddy Katz)
acb6658 Fix: ESLint crash with prefer-object-spread (fixes #10646) (#10649) (薛定谔的猫)

Documentation

dd6cb19 Docs: Updated no-return-await Rule Documentation (fixes #9695) (#10699) (Marla Foreman)
863aa78 Docs: add another example for when not to use no-await-in-loop (#10714) (Valeri Karpov)
6e78b7d Docs: remove links to terminated jscs.info domain (#10706) (Piotr Kuczynski)
8084bfc Docs: change when not to use object spread (#10621) (Benny Powers)
c2bb8bb Docs: Remove superfluous object option sample code (#10652) (Iulian Onofrei)
d34a13b Docs: add subheader in configuring/configuring-rules (#10686) (薛定谔的猫)
99fb7d3 Docs: fix misleading no-prototype-builtins description (#10666) (薛定谔的猫)
005b849 Docs: fix outdated description of baseConfig option (#10657) (Teddy Katz)
15a77c4 Docs: fix broken links (fixes eslint/eslint-jp#6) (#10658) (Toru Nagashima)
87cd344 Docs: Make marking a default option consistent with other rules (#10650) (Iulian Onofrei)
b6daf0e Docs: Remove superfluous section from no-unsafe-negation (#10648) (Iulian Onofrei)

5f6a765 Build: ensure URL fragments remain in documentation links (fixes #10717) (#10720) (Teddy Katz)

Chores

6009239 Chore: rename utils for consistency (#10727) (薛定谔的猫)
5984820 Chore: Move lib/file-finder.js to lib/util/ (refs #10559) (#10695) (Kevin Partington)
7f496e2 Chore: Update require path for ast-utils (#10693) (Kevin Partington)
648a33a Chore: reorganize code structure of utilities (refs #10599) (#10680) (薛定谔的猫)
d8aea28 Chore: rm unnecessary plugin in eslint-config-eslint (#10685) (薛定谔的猫)
0cb5e3e Chore: Replace some function application with spread operators (#10645) (Kevin Partington)
e1a3cac Chore: rm deprecated experimentalObjectRestSpread option in tests (#10647) (薛定谔的猫)

ESLint v5.2.0 released

2018-07-20T00:00:00Z

Highlights

When using the --cache flag, the results for files with linting errors are now saved to the cache. This should result in improved performance when using --cache on a codebase with existing linting errors.

Enhancements

81283d0 Update: Cache files that failed linting (fixes #9948) (#10571) (Kevin Partington)

Documentation

9f93d5f Docs: Updated Working with Custom Formatters (fixes #9950) (#10592) (Marla Foreman)

Dependency Upgrades

13cc63e Upgrade: ignore@4.0.2 (#10619) (Rouven Weßling)
761f802 Upgrade: eslint-plugin-node to 7.0.1 (#10612) (Toru Nagashima)

c517b2a Build: fix npm run perf failing(fixes #10577) (#10607) (薛定谔的猫)
80b296e Build: package.json update for eslint-config-eslint release (ESLint Jenkins)
64dfa21 Build: Fix prerelease logic in blog post generation (fixes #10578) (#10581) (Kevin Partington)

Chores

ac77a80 Chore: Fixing a call to Object.assign.apply in Linter (#10629) (Kevin Partington)
e596939 Chore: fix redundant equality check (#10617) (Toru Nagashima)
9aaf195 Chore: Extract lint result cache logic (refs #9948) (#10562) (Kevin Partington)
e4e7ff2 Chore: fix error message in eslint-config-eslint (#10588) (薛定谔的猫)
1e88170 Chore: Move lib/logging and lib/timing to lib/util/ (refs #10559) (#10579) (Kevin Partington)
0faf633 Chore: Simplify helper method in Linter tests (#10580) (Kevin Partington)

Postmortem for Malicious Packages Published on July 12th, 2018

2018-07-12T00:00:00Z

Summary

On July 12th, 2018, an attacker compromised the npm account of an ESLint maintainer and published malicious versions of the eslint-scope and eslint-config-eslint packages to the npm registry. On installation, the malicious packages downloaded and executed code from pastebin.com which sent the contents of the user’s .npmrc file to the attacker. An .npmrc file typically contains access tokens for publishing to npm.

The malicious package versions are eslint-scope@3.7.2 and eslint-config-eslint@5.0.2, both of which have been unpublished from npm. The pastebin.com paste linked in these packages has also been taken down.

npm has revoked all access tokens issued before 2018-07-12 12:30 UTC. As a result, all access tokens compromised by this attack should no longer be usable.

The maintainer whose account was compromised had reused their npm password on several other sites and did not have two-factor authentication enabled on their npm account.

We, the ESLint team, are sorry for allowing this to happen. We hope that other package maintainers can learn from our mistakes and improve the security of the whole npm ecosystem.

Affected Packages

eslint-scope@3.7, a scope analysis library, is a dependency of several popular packages, including some older versions of eslint and the latest versions of babel-eslint and webpack.
eslint-config-eslint@5.0 is a configuration used internally by the ESLint team, with very little usage elsewhere.

If you run your own npm registry, you should unpublish the malicious versions of each package. They have already been unpublished from the npmjs.com registry.

Attack Method

Further details on the attack can be found here.

Recommendations

With the hindsight of this incident, we have a few recommendations for npm package maintainers and users in the future:

Package maintainers and users should avoid reusing the same password across multiple different sites. A password manager like 1Password or LastPass can help with this.
Package maintainers should enable npm two-factor authentication. npm has a guide here.
- If you use Lerna, you can follow this issue.
Package maintainers should audit and limit the number of people who have access to publish on npm.
Package maintainers should be careful with using any services that auto-merge dependency upgrades.
Application developers should use a lockfile (package-lock.json or yarn.lock) to prevent the auto-install of new packages.

Timeline

Before the incident: The attacker presumably found the maintainer’s reused email and password in a third-party breach and used them to log in to the maintainer’s npm account.
Early morning July 12th, 2018: The attacker generated an authentication token in the maintainer’s npm account.
2018-07-12 9:49 UTC: The attacker used the generated authentication token to publish eslint-config-eslint@5.0.2, which contained a malicious postinstall script that attempts to exfiltrate the local machine’s .npmrc authentication token.
2018-07-12 10:25 UTC: The attacker unpublished eslint-config-eslint@5.0.2.
2018-07-12 10:40 UTC: The attacker published eslint-scope@3.7.2, which contained the same malicious postinstall script.
2018-07-12 11:17 UTC: A user posted eslint/eslint-scope#39, notifying the ESLint team of the issue.
2018-07-12 12:27 UTC: The pastebin.com link containing malicious code was taken down.
2018-07-12 12:37 UTC: The npm team unpublished eslint-scope@3.7.2 after being contacted by an ESLint maintainer.
2018-07-12 17:41 UTC: The ESLint team published eslint-scope@3.7.3 with the code from eslint-scope@3.7.1 so that caches could pick up the new version.
2018-07-12 18:42 UTC: npm revoked all access tokens generated before 2018-07-12 12:30 UTC.

ESLint v5.1.0 released

2018-07-08T00:00:00Z

Highlights

The no-catch-shadow rule has been deprecated in favor of no-shadow.

Enhancements

143890a46 Update: Adjust grammar of error/warnings fixable (#10546) (Matt Mischuk)
b7addf6fe Update: deprecate no-catch-shadow (fixes #10466) (#10526) (Toru Nagashima)

Bug Fixes

b2df73876 Fix: prefer-object-spread duplicated comma (fixes #10512, fixes #10532) (#10524) (Toru Nagashima)
d8c3a25f5 Fix: wrap-regex doesn’t work in some expression(fixes #10573) (#10576) (薛定谔的猫)
63f36f783 Fix: sort-keys in an object that contains spread (fixes #10261) (#10495) (katerberg)
601a5c4ae Fix: Prefer-const rule crashing on array destructuring (fixes #10520) (#10527) (Michael Mason)
02efeac65 Fix: do not fail on nested unknown operators (#10561) (Rubén Norte)
e862dc3a8 Fix: Remove autofixer for no-debugger (fixes #10242) (#10509) (Teddy Katz)

Documentation

114f42ee5 Docs: Clarify option defaults in max-lines-per-function docs (#10569) (Chris Harwood)
100f1beb2 Docs: add note about release issues to readme (#10572) (Teddy Katz)
076a6b6db Docs: add actionable fix to no-irregular-whitespace (#10558) (Matteo Collina)
de663ec14 Docs: Only successfully linted files are cached (fixes #9802) (#10557) (Kevin Partington)
8a2ff2c2e Docs: adding a section about disable rules for some files (#10536) (Wellington Soares)
f22a3f80a Docs: fix a word in no-implied-eval (#10539) (Dan Homola)
20d8bbd49 Docs: add missing paragraph about “custom parsers” (#10547) (Pig Fang)

Dependency Upgrades

f0e22fc05 Upgrade: globals@11.7.0 (#10497) (薛定谔的猫)

7328f9918 Build: package.json update for eslint-config-eslint release (ESLint Jenkins)
b161f6b62 Build: Include prerelease install info in release blog post (#10463) (Kevin Partington)

Chores

8ee39c5f2 Chore: small refactor config-validator (#10565) (薛定谔的猫)
92b19ca61 Chore: use eslintrc overrides(dogfooding) (#10566) (薛定谔的猫)

ESLint v5.0.1 released

2018-06-25T00:00:00Z

Bug Fixes

196c102 Fix: valid-jsdoc should allow optional returns for async (fixes #10386) (#10480) (Mark Banner)

Documentation

4c823bd Docs: Fix max-lines-per-function correct code’s max value (#10513) (Rhys Bower)

ESLint v5.0.0 released

2018-06-22T00:00:00Z

Highlights

There are several breaking changes in 5.0.0. We’ve created a migration guide to explain the breaking changes and describe how to upgrade.
Three new rules have been added:
The CLIEngine.executeOnFiles API now has a globInputPaths option.
The one-var rule is now autofixable.
The array-element-newline rule now has a consistent option.
The camelcase rule now has an ignoreDestructuring option.
The valid-jsdoc rule now has a requireParamType option.
The func-name-matching rule now has a considerPropertyDescriptor option.

Changes since v5.0.0-rc.0:

Features

0feedfd New: Added max-lines-per-function rule (fixes #9842) (#10188) (peteward44)

Enhancements

7a7580b Update: Add considerPropertyDescriptor option to func-name-matching (#9078) (Dieter Luypaert)

Bug Fixes

f93d6ff Fix: do not fail on unknown operators from custom parsers (fixes #10475) (#10476) (Rubén Norte)
05343fd Fix: add parens for yield statement (fixes #10432) (#10468) (Pig Fang)
d477c5e Fix: check destructuring for “no-shadow-restricted-names” (fixes #10467) (#10470) (Pig Fang)
e0a0418 Fix: crash on optional catch binding (#10429) (Toru Nagashima)

Documentation

077358b Docs: no-process-exit: recommend process.exitCode (#10478) (Andres Kalle)
de4dba9 Docs: styling team members (#10460) (薛定谔的猫)
5e453a3 Docs: display team members in tables. (#10433) (薛定谔的猫)
b1895eb Docs: Restore intentional spelling mistake (#10459) (Wilfred Hughes)

Dependency Upgrades

daefbdb Upgrade: eslint-scope and espree to 4.0.0 (refs #10458) (#10500) (Brandon Mills)

ESLint v5.0.0-rc.0 released

2018-06-09T00:00:00Z

Note: This version of ESLint is not ready for production use and is provided to gather feedback from the community before releasing the final version. Please let us know if you having any problems or feedback by creating issues on our GitHub repo or joining our Gitter channel.

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@5.0.0-rc.0 --save-dev

Migration Guide

Enhancements

abf400d Update: Add ignoreDestructing option to camelcase rule (fixes #9807) (#10373) (Andrew Lunny)
640bf07 Update: Fixes multiline no-warning-comments rule. (fixes #9884) (#10381) (Scott Stern)
dc4075e Update: fix false negative in no-use-before-define (fixes #10227) (#10396) (Toru Nagashima)
917108d Update: Add requireParamType option to valid-jsdoc (fixes #6753) (#10220) (Tomasz Sterna)

Bug Fixes

fe8bec3 Fix: fix writing config file when source is prompt (#10422) (Pig Fang)
3e9f33a Fix: prevent crashing from JSON parsing error (fixes #10364) (#10376) (Pig Fang)
636457d Fix: parse later ES files in eslint --init (fixes #10003) (#10378) (Pig Fang)

Documentation

3721841 Docs: Add new experimental syntax policy to README (fixes #9804) (#10408) (Kevin Partington)
d0aae3c Docs: Create docs landing page (#10453) (Kevin Partington)
1984c21 Docs: move custom parsers docs into a page (fixes #9919) (#10431) (Pig Fang)
400d4b5 Docs: Add rest and spread operator changes to migration guide (#10416) (Yannick Croissant)

Dependency Upgrades

e2b394d Upgrade: espree and eslint-scope to rc versions (#10457) (Kevin Partington)
e7bdd02 Upgrade: Consume espree@4.0.0-alpha.1 (#10410) (Kevin Partington)

831c39a Build: Adding rc release script to package.json (#10456) (Kevin Partington)

Chores

a370da2 Chore: small opt to improve readability (#10241) (薛定谔的猫)

ESLint v5.0.0-alpha.4 released

2018-05-28T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@5.0.0-alpha.4 --save-dev

Migration Guide

Features

465e615 New: prompt users before installing dependencies (#10353) (Pig Fang)

Enhancements

93c9a52 Update: config-validator should validate overrides (#10357) (Toru Nagashima)
c2e0398 Update: Improves the prefer-object-spread rule by removing extraneous visitors (#10351) (Sharmila Jesupaul)
d848949 Update: Support JSXFragment node (fixes #9662) (#9664) (Clement Hoang)
9c922ce Update: Add “consistent” option to array-element-newline (fixes #9457) (#10355) (Pig Fang)

Bug Fixes

240c1a4 Fix: prefer-const object destructuring false positive (fixes #9108) (#10368) (Pig Fang)
65bce3a Fix: ensure --stdin flag works when stdin is piped asynchronously (#10393) (Teddy Katz)
8b7a70c Fix: handle one-var with no semicolon (fixes #10330) (#10371) (Malcolm Groves)
fb148aa Fix: allow no tokens after return keyword (fixes #10372) (#10379) (Pig Fang)
a812845 Fix: allow array spread for prefer-object-spread rule (fixes #10344) (#10347) (Pig Fang)

Documentation

ce3e62a Docs: remove test coverage badge (#10407) (薛定谔的猫)
074bc1c Docs: polish for max-classes-per-file rule (#10377) (Pig Fang)
448fc52 Docs: Update link to Integrations / Build tools / Start (#10354) (Kir Belevich)

f268128 Build: add Node v10 to travis (#10262) (alberto)

Chores

b9b23a9 Chore: rm unused argument (#10400) (薛定谔的猫)
e25fc22 Chore: remove assert.doesNotThrow in tests (#10199) (Ruben Bridgewater)
4e5e9be Chore: avoid unnecessary filesystem accesses during config search (#10359) (Teddy Katz)
363da01 Chore: avoid code duplication in rule severity checking (#10358) (Teddy Katz)

ESLint v5.0.0-alpha.3 released

2018-05-11T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Two new rules have been added: prefer-object-spread and max-classes-per-file
The CLIEngine API now supports a globInputPaths option to disable glob resolution when linting files.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@5.0.0-alpha.3 --save-dev

Migration Guide

Breaking Changes

41f0f6e Breaking: report multiline eslint-disable-line directives (fixes #10334) (#10335) (Teddy Katz)
09dde26 Breaking: new object-curly-newline/no-self-assign default (fixes #10215) (#10337) (Teddy Katz)

Features

1a6b399 New: Adds prefer-object-spread rule (refs: #7230) (#9955) (Sharmila Jesupaul)
c4109b2 New: add max-classes-per-file rule (#10163) (James Garbutt)
514013c New: Add globInputPaths CLIEngine option (fixes #9972) (#10191) (Pierre Vanduynslager)

Enhancements

e5b33be Update: Add --fix for one-var rule (refs #9072) (#10040) (Sebastian Malton)

Bug Fixes

d65f11d Fix: correct comma fix in spare array (fixes #10273) (#10329) (Malcolm Groves)
c343d86 Fix: do not autofix octal escape sequence (fixes #10031) (#10240) (Malcolm Groves)
bb6090f Fix: Throw error when --ignore-path not a file (fixes #10076) (#10205) (Malcolm Groves)

Documentation

82757b2 Docs: Adding a little guidance to rule documentation (#10301) (Justin)
2f30aa5 Docs: add a better vim linting engine (#10292) (Jon Smithers)
df2c1fb Docs: improve formatter guide (refs #9550) (#10294) (Dominic Lee)
a960d69 Docs: remove outdated notes from migration guide (#10279) (Teddy Katz)

1b6b2b2 Build: remove trailing spaces in blogpost template (#10280) (Teddy Katz)

Chores

4ccd25a Chore: add eslint-plugin-node to eslint-config-eslint(fixes #10319) (#10320) (薛定谔的猫)
02e7b28 Chore: upgrade deps (#10339) (薛定谔的猫)
1397179 Chore: unskip test for scope analysis (#10336) (Teddy Katz)
99b842d Chore: upgrade mock-fs@4.5.0 (#10325) (Tim Schaub)
fe91859 Chore: Update issue templates with new format (#10309) (Ilya Volodin)
f7330c1 Chore: Add ESLint path to plugin-missing message (#10283) (Kevin Partington)

ESLint v5.0.0-alpha.2 released

2018-04-27T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@5.0.0-alpha.2 --save-dev

Migration Guide

Breaking Changes

02e44a5 Breaking: remove TDZ scopes (fixes #10245) (#10270) (Toru Nagashima)
c74933b Breaking: remove extra check in getScope (fixes #10246, fixes #10247) (#10252) (Toru Nagashima)
8b7c6ea Breaking: report fatal error for linting nonexistent files (fixes #7390) (#10143) (Teddy Katz)
9100819 Breaking: fix plugin resolver in extends (fixes #9904) (#10236) (Toru Nagashima)
c45f1d0 Breaking: add rules to recommended (fixes #8865) (#10158) (薛定谔的猫)

Enhancements

a82cbea Update: re-enable experimentalObjectRestSpread (fixes #9990) (#10230) (Toru Nagashima)

Bug Fixes

1d443a0 Fix: valid-jsdoc does not know async function returns (fixes #9881) (#10161) (Rachael Sim)
f9c7371 Fix: do not autofix object-shorthand with comments (fixes #10038) (#10238) (Malcolm Groves)

Documentation

510ca8b Docs: make grammatical tweaks in migration guide (#10278) (Teddy Katz)
8799972 Docs: make template link wording more clear (#10219) (David Luzar)
4672b56 Docs: Correct wording in the smart-tabs docs page (#10277) (Jed Fox)
85a5191 Docs: Update JSCS FAQ (#10221) (alberto)
8e89d5c Docs: Fix typo (#10223) (alberto)
c0c331e Docs: Add Prettier to FAQ (#10222) (alberto)
2443627 Docs: add backticks in getter-return (#10218) (薛定谔的猫)
74bb5b5 Docs: Fix misspelling in changelog (#10216) (Kevin Partington)

Chores

7c2e83a Chore: improve tests and checking for equality (#10182) (Ruben Bridgewater)
b32d1f4 Chore: upgrade eslump@1.6.2 (#10258) (薛定谔的猫)
7938bf1 Chore: update eslint-fuzzer ecmaVersion to 2018 (#10255) (薛定谔的猫)
a2953ec Chore: small opt to improve readability (#10225) (薛定谔的猫)

ESLint v5.0.0-alpha.1 released

2018-04-13T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@5.0.0-alpha.1 --save-dev

Migration Guide

Breaking Changes

b2a48a9 Breaking: stop using fake context._linter property (fixes #10140) (#10209) (Teddy Katz)
a039956 Breaking: remove deprecated browser/jest/node globals (fixes #10141) (#10210) (Teddy Katz)
2324570 Breaking: no-unused-vars reports all after-used params (fixes #9909) (#10119) (Kevin Partington)
b77846d Breaking: drop supporting Node.js 4 (fixes #10052) (#10074) (薛定谔的猫)

Bug Fixes

218ee57 Fix: report no-case-declarations from declarations (fixes #10048) (#10167) (Carlo Abelli)

Documentation

98f1cad Docs: update migration guide with latest changes (#10212) (Teddy Katz)
71167be Docs: fix wrong config in id-length (#10196) (薛定谔的猫)
731da1e Docs: fix code in correct example. (#10195) (薛定谔的猫)
3780915 Docs: fix some small errors in examples (#10194) (薛定谔的猫)
1e7252f Docs: Add more related rules for object-curly-spacing (#10175) (Saugat Acharya)
e5cf9cc Docs: Reorder README sections (#10172) (alberto)
d0dc2e3 Docs: Add Missing Quotes (#10162) (Samarth Verma)

Dependency Upgrades

f595fd8 Upgrade: upgrade deps (#10184) (alberto)
7765fc4 Upgrade: ajv@^6.0.1, still using json schema draft 04 (#9856) (Kevin Partington)
869c9f5 Upgrade: babelify (#10185) (alberto)
b7ee1ed Upgrade: upgrade devdeps (#10178) (alberto)
f3a0291 Upgrade: Update dependencies. (#10168) (alberto)
7d6e052 Upgrade: esquery@^1.0.1 (fixes #8733) (#10170) (Kevin Partington)
7a63bfa Upgrade: eslint-release to v0.11.1 (#10156) (Teddy Katz)

b7a1a7a Build: Gensite creates prerelease dirs if needed (#10154) (Brandon Mills)

Chores

2e60017 Chore: remove concat-stream dependency (#10173) (Teddy Katz)
7f69f11 Chore: rearrange init options. (#10131) (薛定谔的猫)
81629d2 Chore: enable rest/spread rules on ESLint codebase (#10211) (Teddy Katz)
cd34d44 Chore: avoid modifying global state when tests fail (#10201) (Teddy Katz)
db1a582 Chore: Add debug logging for CLI args as they came in (#10174) (Kevin Partington)
c85578f Chore: Remove esprima-fb dependency. (#10171) (alberto)

ESLint v5.0.0-alpha.0 released

2018-03-30T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@5.0.0-alpha.0 --save-dev

Migration Guide

Breaking Changes

f4b3af586 Breaking: Upgrade to Espree v4 alpha (refs #9990) (#10152) (Brandon Mills)
d440e8496 Breaking: support @scope shorthand in plugins (fixes #9903) (#9905) (Toru Nagashima)
a9ee9ae87 Breaking: require rules to provide report messages (fixes #10011) (#10057) (Teddy Katz)
c383bc57f Breaking: Make require(‘eslint’).linter non-enumerable (fixes #9270) (#9692) (Jed Fox)
4eaebe5ae Breaking: set parent of AST nodes before rules run (fixes #9122) (#10014) (Teddy Katz)
91ece32ac Breaking: remove special exception for linting empty files (fixes #9534) (#10013) (Teddy Katz)
27e3f24d8 Breaking: remove source property from linting messages (fixes #7358) (#10012) (Teddy Katz)
e4c3b3c56 Breaking: use an exit code of 2 for fatal config problems (fixes #9384) (#10009) (Teddy Katz)
2a7ecaa2a Breaking: Use strict equality in RuleTester comparisons (fixes #9417) (#10008) (Teddy Katz)

Enhancements

462b058d0 Update: Include debugging information when rule throws error (#9742) (Patrick Hayes)
ea6fb17ae Update: Make no-cond-assign work for ternaries (fixes #10091) (#10109) (Aaron Harper)

Bug Fixes

0bc4a3835 Fix: Make rule-tester strictly check messageId. (ref #9890) (#9908) (Jacques Favreau)

Documentation

3351129f9 Docs: add v5.0.0 migration guide (fixes #10142) (#10147) (Teddy Katz)
65cc83498 Docs: Ensure CLI doc sections match command line help order (#10144) (Kevin Partington)
9c791746b Docs: Update capitalized-comments with missing letters (fixes #10135) (#10134) (jasonfry)
9e66bfbc4 Docs: remove eslint vs jshint from faq (#10108) (alberto)
692e3830b Docs: Add modified variable examples for no-loop-func (fixes #9527) (#10098) (Rachael Sim)

f2f98dd13 Build: make prerelease script publish to GitHub/website (#10151) (Teddy Katz)

Chores

9a020dc14 Chore: refactor --no-ignore flag logic (#10146) (Teddy Katz)
4f61a0ded Chore: add noopener/noreferrer (薛定谔的猫)
837edc7c0 Chore: Uncommented test for empty program for no-invalid-meta (#10046) (Kevin Partington)

ESLint v4.19.1 released

2018-03-21T00:00:00Z

Bug Fixes

3ff5d11 Fix: no-invalid-regexp not understand variable for flags (fixes #10112) (#10113) (薛定谔的猫)
abc765c Fix: object-curly-newline minProperties w/default export (fixes #10101) (#10103) (Kevin Partington)

Documentation

6f9e155 Docs: Update ambiguous for…in example for guard-for-in (#10114) (CJ R)

Chores

0360cc2 Chore: Adding debug logs on successful plugin loads (#10100) (Kevin Partington)
a717c5d Chore: Adding log at beginning of unit tests in Makefile.js (#10102) (Kevin Partington)

ESLint v4.19.0 released

2018-03-16T00:00:00Z

The one-var rule now has a consecutive option.
Core rules have been updated to support the new RegExp features introduced in ES2018 (when using the appropriate parser options).

Enhancements

55a1593 Update: consecutive option for one-var (fixes #4680) (#9994) (薛定谔的猫)
2e68be6 Update: give a node at least the indentation of its parent (fixes #9995) (#10054) (Teddy Katz)
72ca5b3 Update: Correctly indent JSXText with trailing linebreaks (fixes #9878) (#10055) (Teddy Katz)

Bug Fixes

8d3814e Fix: false positive about ES2018 RegExp enhancements (fixes #9893) (#10062) (Toru Nagashima)

Documentation

935f4e4 Docs: Clarify default ignoring of node_modules (#10092) (Matijs Brinkhuis)
72ed3db Docs: Wrap Buffer() in backticks in no-buffer-constructor rule description (#10084) (Stephen Edgar)
3aded2f Docs: Fix lodash typos, make spacing consistent (#10073) (Josh Smith)
66a1e9a Docs: fix possible typo (#10060) (Vse Mozhet Byt)
2a4c838 Docs: Update ECMAScript versions in FAQ (#10047) (alberto)

Chores

e33bb64 Chore: enable no-param-reassign on ESLint codebase (#10065) (Teddy Katz)

ESLint v4.18.2 released

2018-03-02T00:00:00Z

Bug Fixes

6b71fd0 Fix: table@4.0.2, because 4.0.3 needs “ajv”: “^6.0.1” (#10022) (Mathieu Seiler)
f6901d0 Fix: remove catastrophic backtracking vulnerability (fixes #10002) (#10019) (Jamie Davis)
aea07dc Fix: Make max-len ignoreStrings ignore JSXText (fixes #9954) (#9985) (Rachael Sim)

Chores

3c697de Chore: fix incorrect comment about linter.verify return value (#10030) (Teddy Katz)
9df8653 Chore: refactor parser-loading out of linter.verify (#10028) (Teddy Katz)
e4f52ce Chore: Simplify dataflow in linter.verify (#10020) (Teddy Katz)
33177cd Chore: make library files non-executable (#10021) (Teddy Katz)
558ccba Chore: refactor directive comment processing (#10007) (Teddy Katz)
18e15d9 Chore: avoid useless catch clauses that just rethrow errors (#10010) (Teddy Katz)
a1c3759 Chore: refactor populating configs with defaults in linter (#10006) (Teddy Katz)

ESLint v4.18.1 released

2018-02-20T00:00:00Z

Bug Fixes

f417506 Fix: ensure no-await-in-loop reports the correct node (fixes #9992) (#9993) (Teddy Katz)

Documentation

3e99363 Docs: Fixed typo in key-spacing rule doc (#9987) (Jaid)
7c2cd70 Docs: deprecate experimentalObjectRestSpread (#9986) (Toru Nagashima)

ESLint v4.18.0 released

2018-02-16T00:00:00Z

Enhancements

0e4ae22 Update: fix indent bug with binary operators/ignoredNodes (fixes #9882) (#9951) (Teddy Katz)
47ac478 Update: add named imports and exports for object-curly-newline (#9876) (Nicholas Chua)
4a6f22e Update: support eslint-disable-* block comments (fixes #8781) (#9745) (Erin)

Bug Fixes

e8efdd0 Fix: support Rest/Spread Properties (fixes #9885) (#9943) (Toru Nagashima)
f012b8c Fix: support Async iteration (fixes #9891) (#9957) (Toru Nagashima)

Documentation

74fa253 Docs: Clarify no-mixed-operators options (fixes #9962) (#9964) (Ivan Hayes)
426868f Docs: clean up key-spacing docs (fixes #9900) (#9963) (Abid Uzair)
777283b Docs: Propose fix typo for function (#9965) (John Eismeier)
bf3d494 Docs: Fix typo in max-len ignorePattern example. (#9956) (Tim Martin)
d64fbb4 Docs: fix typo in prefer-destructuring.md example (#9930) (Vse Mozhet Byt)

Chores

70f22f3 Chore: Apply memoization to config creation within glob utils (#9944) (Kenton Jacobsen)
f8d343f Chore: Fix default issue template (#9946) (Kai Cataldo)

ESLint v4.17.0 released

2018-02-02T00:00:00Z

Highlights

A new multiline option has been added to the padding-line-between-statements rule.

Enhancements

1da1ada Update: Add “multiline” type to padding-line-between-statements (#8668) (Matthew Bennett)
dc80487 Update: space-unary-ops uses astUtils.canTokensBeAdjacent (fixes #9907) (#9906) (Kevin Partington)

Bug Fixes

d20f6b4 Fix: Typo in error message when running npm (#9866) (Maciej Kasprzyk)

Documentation

1aa1970 Docs: remove outdated rule naming convention (#9925) (Teddy Katz)
3afaff6 Docs: Add prefer-destructuring variable reassignment example (#9873) (LePirlouit)
51ec6a7 Docs: Use GitHub Multiple PR/Issue templates (#9911) (Kai Cataldo)
084351b Docs: Fix the messageId example (fixes #9889) (#9892) (Jed Fox)
9cbb487 Docs: Mention the globals key in the no-undef docs (#9867) (Dan Dascalescu)

Chores

bb213dc Chore: Use messageIds in some of the core rules (#9648) (Jed Fox)

ESLint v4.16.0 released

2018-01-19T00:00:00Z

Highlights

The comma-style rule now supports a NewExpression option.
The valid-jsdoc rule can now be autofixed in some cases, and its error locations are more precise.
The allowMultiplePropertiesPerLine option in the object-property-newline rule has been renamed to allowAllPropertiesOnSameLine to more clearly convey what the option does. allowMultiplePropertiesPerLine still works, but has been deprecated.

Enhancements

e26a25f Update: allow continue instead of if wrap in guard-for-in (fixes #7567) (#9796) (Michael Ficarra)
af043eb Update: Add NewExpression support to comma-style (#9591) (Frazer McLean)
1d61930 Update: use doctrine range information in valid-jsdoc (#9831) (Teddy Katz)
133336e Update: fix indent behavior on template literal arguments (fixes #9061) (#9820) (Teddy Katz)
add1e70 Update: fix indent bug on comments in ternary expressions (fixes #9729) (#9818) (Teddy Katz)
2cf4522 Update: Rename and deprecate object-property-newline option (#9570) (Jonathan Pool)

Bug Fixes

13bcf3c Fix: Removing curly quotes in no-eq-null report message (#9852) (Kevin Partington)
ea1b15d Fix: avoid crashing on malformed configuration comments (fixes #9373) (#9819) (Teddy Katz)
6a5cd32 Fix: prefer-destructuring error with computed properties (fixes #9784) (#9817) (Teddy Katz)

Documentation

b96fb31 Docs: configuration hierarchy for CLIEngine options (fixes #9526) (#9855) (PiIsFour)
8ccbdda Docs: Clarify that -c configs merge with .eslintrc.* (fixes #9535) (#9847) (Kevin Partington)
978574f Docs: Fix examples for no-useless-escape (#9853) (Toru Kobayashi)
2e87ddd Docs: Sync messageId examples’ style with other examples (#9816) (Kevin Partington)
601f851 Docs: Minor modification to code comments for clarity (#9821) (rgovind92)
b9da067 Docs: fix misleading info about RuleTester column numbers (#9830) (Teddy Katz)
acde640 Docs: Add ES 2018 to Configuring ESLint (#9829) (Kai Cataldo)
ccfce15 Docs: Minor tweaks to working with rules page (#9824) (Kevin Partington)
54b329a Docs: fix substitution of {{ name }} (#9822) (Andres Kalle)

4f898c7 Build: Fix JSDoc syntax errors (#9813) (Matija Marohnić)

Chores

cd5681d Chore: Deactivate consistent-docs-url in internal rules folder (#9815) (Kevin Partington)

ESLint v4.15.0 released

2018-01-06T00:00:00Z

Highlights

New APIs

CLIEngine now has a getRules() method. This is useful for integrations that need to look at rules’ metadata programmatically without knowing what rules might have been defined by plugins.

Rules now support messages metadata and messageId report parameters, including full support in RuleTester. This lets rule developers use messageIds in their rule tests and avoid needing to track report message changes in both the rule implementation and the corresponding test file. In addition, this is the first step towards core support for rule message localization.

New rule options

The indent rule now has an ignoreComments option. This allows users to opt out of indentation checks for comments if project style rules require that comments be indented in a different manner.

Features

6ab04b5 New: Add context.report({ messageId }) (fixes #6740) (#9165) (Jed Fox)
65f0176 New: CLIEngine#getRules() (refs #6582) (#9782) (Patrick McElhaney)

Enhancements

c64195f Update: More detailed assert message for rule-tester (#9769) (Weijia Wang)
bbabf34 Update: add ignoreComments option to indent rule (fixes #9018) (#9752) (Kevin Partington)

Bug Fixes

9fcfabf Fix: no-extra-parens false positive (fixes: #9755) (#9795) (Erin)
4c87f42 Fix: incorrect error messages of no-unused-vars (fixes #9774) (#9791) (akouryy)

Documentation

fc7f404 Docs: add url to each of the rules (refs #6582) (#9788) (Patrick McElhaney)
fc44da9 Docs: fix sort-imports rule block language (#9805) (ferhat elmas)
61e5fa0 Docs: Add table of contents to Node.js API docs (#9785) (Patrick McElhaney)
db431cb Docs: HTTP -> HTTPS (fixes #9768) (#9768) (Ronald Eddy Jr)
cbf0fb9 Docs: describe how to feature-detect scopeManager/visitorKeys support (#9764) (Teddy Katz)
f7dcb70 Docs: Add note about “patch release pending” label to maintainer guide (#9763) (Teddy Katz)

ESLint v4.14.0 released

2017-12-23T00:00:00Z

Highlights

Parsers can now provide custom scope analysis hooks to ESLint, which should allow for easier integration when parsing non-standard syntax. For more information see our documentation.

Features

ae51eb2 New: Add allowImplicit option to array-callback-return (fixes #8539) (#9344) (James C. Davis)

Enhancements

be2f57e Update: support separate requires in one-var. (fixes #6175) (#9441) (薛定谔的猫)
75c7419 Update: Logical-and is counted in complexity rule (fixes #8535) (#9754) (Kevin Partington)
1c2aafd Update: Improve parser integrations (fixes #8392) (#8755) (Toru Nagashima)

Bug Fixes

43d4ba8 Fix: false positive on rulelines-between-class-members (fixes #9665) (#9680) (sakabar)

Documentation

370d614 Docs: Fix typos (#9751) (Jed Fox)
eb4b1e0 Docs: reintroduce misspelling in valid-typeof example (#9753) (Teddy Katz)
e9d5dfd Docs: improve no-extra-parens formatting (#9747) (Rich Trott)
f252c19 Docs: Make the lint message source property a little more subtle (#9735) (Jed Fox)
5a5c23c Docs: fix the link to contributing page (#9727) (Victor Hom)
f44ce11 Docs: change beginner to good first issue label text (#9726) (Victor Hom)
f819920 Docs: fix typos (#9723) (Thomas Broadley)

Dependency Upgrades

4ddc131 Upgrade: debug@^3.1.0 (#9731) (Kevin Partington)

Chores

8196c45 Chore: Reorganize CLI options and associated docs (#9758) (Kevin Partington)
37d066c Chore: Add unit tests for overrides glob matching. (#9744) (Robert Jackson)
805a94e Chore: Fix typo in CLIEngine test name (#9741) (@scriptdaemon)
14baa2e Chore: improve arrow-body-style error message (refs #5498) (#9718) (Teddy Katz)

ESLint v4.13.1 released

2017-12-11T00:00:00Z

Bug Fixes

b72dc83 Fix: eol-last allow empty-string to always pass (refs #9534) (#9696) (Kevin Partington)
d80aa7c Fix: camelcase destructure leading/trailing underscore (fixes #9700) (#9701) (Kevin Partington)

Documentation

d49d9d0 Docs: Add missing period to the README (#9702) (Kevin Partington)

Chores

4564fe0 Chore: no-invalid-meta crash if no export assignment (refs #9534) (#9698) (Kevin Partington)

ESLint v4.13.0 released

2017-12-08T00:00:00Z

Highlights

This release updates camelcase rule to handle destructuring by default, which might result in more user-visible errors.

Enhancements

256481b Update: update handling of destructuring in camelcase (fixes #8511) (#9468) (Erin)

Documentation

d067ae1 Docs: Don’t use undocumented array-style configuration for max-len (#9690) (Jed Fox)
cdb1488 Docs: Adds an example with try/catch. (#9672) (Jaap Taal)

Chores

1ad3091 Chore: fix test-suite to work with node master (#9688) (Myles Borins)

ESLint v4.12.1 released

2017-11-30T00:00:00Z

Bug Fixes

1e362a0 Revert “Fix: Use XML 1.1 on XML formatters (fixes #9607) (#9608)” (#9667) (Kevin Partington)

ESLint v4.12.0 released

2017-11-25T00:00:00Z

Highlights

New Rules

We’ve added 1 new rule with this release:

implicit-arrow-linebreak

Autofixable Rules

We’ve added autofix capabilities to one rule: sort-vars. At present, it will only sort variables with no initial value or a literal initial value, in order to avoid potentially changing the order of function calls.

New Node.js APIs

We’ve added a new Node.js API:

Linter.defineParser

This API is useful when you are working with an instance of Linter and need to define a custom parser at runtime.

Features

28c9c8e New: add a Linter#defineParser function (#9321) (Ives van Hoorne)
4118f14 New: Adds implicit-arrow-linebreak rule (refs #9510) (#9629) (Sharmila Jesupaul)

Enhancements

5619910 Update: Add autofix for sort-vars (#9496) (Trevin Hofmann)
71eedbf Update: add beforeStatementContinuationChars to semi (fixes #9521) (#9594) (Toru Nagashima)
0cf081e Update: add importNames option to no-restricted-imports (#9506) (Benjamin R Gibson)

Bug Fixes

208fb0f Fix: Use XML 1.1 on XML formatters (fixes #9607) (#9608) (Daniel Reigada)
e13d439 Fix: space-in-parens crash (#9655) (Toru Nagashima)
a015234 Fix: prefer-destructuring false positive on “super” (fixes #9625) (#9626) (Kei Ito)

Documentation

92171cc Docs: Updating migration guide for single-line disable (#9385) (Justin Helmer)
f39ffe7 Docs: remove extra punctuation from readme (#9640) (Teddy Katz)
332c214 Docs: Add @platinumazure to TSC (#9618) (Ilya Volodin)

Dependency Upgrades

76dab18 Upgrade: doctrine@^2.0.2 (#9656) (Kevin Partington)
6e04f14 Upgrade: globals to 11.0.1 (fixes #9614) (#9632) (Toru Nagashima)

ESLint v4.11.0 released

2017-11-10T00:00:00Z

Highlights

npm installed formatters can now be specified with or without the package name’s eslint-formatter- prefix. Example:

npm install eslint-formatter-pretty

eslint -f pretty file.js

// equivalent:
eslint -f eslint-formatter-pretty file.js

Enhancements

4d7d7ab Update: Resolve npm installed formatters (#5900) (#9464) (Tom Erik Støwer)

Bug Fixes

7e3bf6a Fix: edge-cases of semi-style (#9560) (Toru Nagashima)
e5a37ce Fix: object-curly-newline for flow code (#9458) (Tiddo Langerak)
b7c5b19 Fix: Correct [object Object] output of error.data. (#9561) (Jonathan Pool)
accc490 Fix: Files with no failures get “passing” testcase (#9547) (Samuel Levy)
a9606a3 Fix: invalid tests with super (fixes #9539) (#9545) (Teddy Katz)

Documentation

d4557a6 Docs: disallow use of the comma operator using no-restricted-syntax (#9585) (薛定谔的猫)
6672fae Docs: Fixed a typo on lines-between-class-members doc (#9603) (Moinul Hossain)
2542f04 Docs: Add missing options for lines-around-comment (#9589) (Clément Fiorio)
51c8cf0 Docs: Disambiguate definition of Update tag (#9584) (Jonathan Pool)
afc3c75 Docs: clarify what eslint-config-eslint is (#9582) (Teddy Katz)
aedae9d Docs: fix spelling in valid-typeof example (#9574) (Maksim Degtyarev)
4c5aaf3 Docs: Fix typo in no-underscore-dangle rule (#9567) (Fabien Lucas)
ab0f66d Docs: Add examples to better show rule coverage. (#9548) (Jonathan Pool)
acccfbd Docs: Minor rephrase in no-invalid-this. (#9542) (Francisc)
8f9c0fe Docs: improve id-match usage advice (#9544) (Teddy Katz)
06b491e Docs: fix duplicate entries in changelog (#9530) (Teddy Katz)
9cf4ebe Docs: add .md to link(for github users) (#9529) (薛定谔的猫)

Dependency Upgrades

d602f9e Upgrade: espree v3.5.2 (#9611) (Kai Cataldo)

cc2c7c9 Build: use Node 8 in appveyor (#9595) (薛定谔的猫)
b6a7490 Build: ensure fuzzer tests get run with npm test (#9590) (Teddy Katz)
1073bc5 Build: remove shelljs-nodecli (refs #9533) (#9588) (Teddy Katz)
7f37b1c Build: test Node 9 on Travis (#9556) (Teddy Katz)

Chores

4def876 Chore: avoid handling rules instances in config-validator (#9364) (Teddy Katz)
fe5ac7e Chore: fix incorrect comment in safe-emitter.js (#9605) (Teddy Katz)
980ecd3 Chore: Update copyright and license info (#9599) (薛定谔的猫)
9064b9c Chore: add equalTokens in ast-utils. (#9500) (薛定谔的猫)
3623600 Chore: upgrade ajv@5.3.0 (#9557) (薛定谔的猫)
1b606cd Chore: Remove an indirect dependency on jsonify (#9444) (Rouven Weßling)
88d2303 Chore: Add object-property-newline tests to increase coverage. (#9553) (Jonathan Pool)
8e1a095 Chore: enable a modified version of multiline-comment-style on codebase (#9452) (Teddy Katz)
cb60285 Chore: remove commented test for HTML formatter (#9532) (Teddy Katz)
2224733 Chore: use eslint-plugin-rulesdir instead of --rulesdir for self-linting (#9164) (Teddy Katz)

ESLint v4.10.0 released

2017-10-27T00:00:00Z

Enhancements

ebb530d Update: Don’t ignore comments (no-trailing-spaces) (#9416) (Chris van Marle)

Bug Fixes

bb6e60a Fix: Improve the doc for no-restricted-modules rule (fixes #9437) (#9495) (vibss2397)
d80b9d0 Fix: no-var don’t fix globals (fixes #9520) (#9525) (Toru Nagashima)
b8aa071 Fix: allow linting the empty string from stdin (fixes #9515) (#9517) (Teddy Katz)
2fa64b7 Fix: should not convert non-consecutive line comments to a single blo… (#9475) (薛定谔的猫)
9725146 Fix: multiline-comment-style fix produces invalid code (fixes #9461). (#9463) (薛定谔的猫)
b12cff8 Fix: Expected order of jsdoc tags (fixes #9412) (#9451) (Orlando Wenzinger)
8768b2d Fix: multiline-comment-style autofixer added trailing space (#9454) (Teddy Katz)
e830aa1 Fix: multiline-comment-style reports block comments followed by code (#9450) (Teddy Katz)
eb8cfb1 Fix: change err report in constant condition (fixes #9398) (#9436) (Victor Hom)

Documentation

c529de9 Docs: Amend rule document to correct and complete it (refs #6251). (#9498) (Jonathan Pool)
7d390b2 Docs: Revise contributor documentation on issue labels. (#9469) (Jonathan Pool)
720b6d5 Docs: Update ISSUE_TEMPLATE.md (#9504) (薛定谔的猫)
f054ab5 Docs: add .md to link (for github users) (#9501) (薛定谔的猫)
5ed9cfc Docs: Correct violations of “Variable Declarations” in Code Conventions (#9447) (Jonathan Pool)
3171097 Docs: Clears confusion on usage of global and local plugins.(#9492) (Vasili Sviridov)
0f71fef Docs: Unquote booleans in lines-between-class-members docs (#9497) (Brandon Mills)
b3d7532 Docs: use consistent terminology & fix link etc. (#9490) (薛定谔的猫)
87db8ae Docs: Fix broken links (#9488) (gpiress)
51bdb2f Docs: Incorrect link to related rule (#9477) (Gavin King)
1a962e8 Docs: Add FAQ for when ESLint cannot find plugin (#9467) (Kevin Partington)
b12e5fe Docs: Repair broken links and add migration links. (#9473) (Jonathan Pool)
eca01ed Docs: Add missing info about special status of home-dir config files. (#9472) (Jonathan Pool)
47e5f6f Docs: ensure “good commit message” examples actually follow guidelines (#9466) (Teddy Katz)
ecac0fd Docs: Remove blockBindings references (#9446) (Jan Pilzer)
052c504 Docs: suggest deleting branches after merging PRs (#9449) (Teddy Katz)
a7521e3 Docs: improve examples for multiline-comment-style (#9440) (Teddy Katz)

5012661 Build: fix npm run profile script (fixes #9397) (#9455) (Teddy Katz)
b6f31a9 Build: changelog update for 4.9.0 (ESLint Jenkins)

Chores

f9c6673 Chore: Add tests to cover array and object values and leading commas. (#9502) (Jonathan Pool)
9169258 Chore: remove npm run check-commit script (#9513) (Teddy Katz)
350a72c Chore: regex.test => string.startsWith (#9518) (薛定谔的猫)
de0bef4 Chore: remove obsolete eslintbot templates (#9512) (Teddy Katz)
3204773 Chore: enable max-len. (#9414) (薛定谔的猫)
da77eb4 Chore: Revise no-config-file test to prevent false failure. (#9443) (Jonathan Pool)
0b89865 Chore: ensure tests for internal rules get run (#9453) (Teddy Katz)
b31e55a Chore: move internal rules out of lib/ (#9448) (Teddy Katz)

ESLint v4.9.0 released

2017-10-14T00:00:00Z

Highlights

We’ve added 2 new rules with this release:

We also added new CLI option --fix-dry-run. This option will allow you to apply fixes without writing them to the disk.

Features

8eb4aae New: multiline-comment-style rule (fixes #8320) (#9389) (薛定谔的猫)
ee99876 New: lines-between-class-members rule (fixes #5949) (#9141) (薛定谔的猫)
4567ab1 New: Add the fix-dry-run flag (fixes #9076) (#9073) (Rafał Ruciński)

Enhancements

2247efa Update: Add FunctionExpression to require-jsdoc (fixes #5867) (#9395) (Kai Cataldo)
b02fbb6 Update: custom messages for no-restricted-* (refs #8400) (Maja Wichrowska)
6767857 Update: fix ignored nodes in indent rule when using tabs (fixes #9392) (#9393) (Robin Houston)
786cc73 Update: Add “consistent” option to array-bracket-newline (fixes #9136) (#9206) (Ethan Rutherford)
1167638 Update: add allowElseIf option to no-else-return (fixes #9228) (#9229) (Thomas Grainger)
62a323c Fix: Add class options for lines-around-comment (fixes #8564) (#8565) (Ed Lee)

Bug Fixes

85388fb Fix: Correct error and test messages to fit config search path (#9428) (Jonathan Pool)
8da525f Fix: recognise multiline comments as multiline arrays (fixes #9211) (#9369) (Phil Quinn)

Documentation

6791d18 Docs: Corrected noun to verb. (#9438) (Jonathan Pool)
02732bd Docs: Reorganized to avoid misunderstandings. (#9434) (Jonathan Pool)
d9466b8 Docs: Correct time forecast for tests. (#9432) (Jonathan Pool)
f7ed84f Docs: Add instruction re home-directory config files (refs #7729) (#9426) (Jonathan Pool)
2d8a303 Docs: fix examples for prefer-numeric-literals (#9155) (Lutz Lengemann)
d7610f5 Docs: Add jquery warning to prefer-destructuring (#9409) (Thomas Grainger)
e835dd1 Docs: clarify no-mixed-operators (fixes #8051) (Ruxandra Fediuc)
51360c8 Docs: update block-spacing details (fixes #8743) (#9375) (Victor Hom)
7654c99 Docs: add installing prerequisites in readme. (#9401) (薛定谔的猫)
e171f6b Docs: add installing prerequisites. (#9394) (薛定谔的猫)
74dfc87 Docs: update doc for class-methods-use-this (fixes #8910) (#9374) (Victor Hom)
b4a9dbf Docs: show console call with no-restricted-syntax (fixes #7806) (#9376) (Victor Hom)

Chores

db41408 Chore: avoid applying eslint-env comments twice (#9278) (Teddy Katz)
febb897 Chore: avoid loose equality assertions (#9415) (Teddy Katz)
30d018b Chore: Add Aladdin-ADD & VictorHom to README (#9424) (Kai Cataldo)
37dde77 Chore: Refactor SourceCode#getJSDocComment (#9403) (Kai Cataldo)
9fedd51 Chore: Add missing space in blog post template (#9407) (Kevin Partington)
c581b77 Chore: Error => TypeError (#9390) (薛定谔的猫)
9d3f5ad Chore: report unused eslint-disable directives in ESLint codebase (#9371) (Teddy Katz)

ESLint v4.8.0 released

2017-09-29T00:00:00Z

Highlights

–report-unused-disable-directives

This release includes a new CLI option that, when on, reports unused eslint-disable directives! Running this periodically will ensure that all eslint-disable comments are still relevant and up to date.

Please see the documentation for more information.

Features

3f2b908 New: add option to report unused eslint-disable directives (fixes #9249) (#9250) (Teddy Katz)

Bug Fixes

ff2be59 Fix: dot notation rule failing to catch string template (fixes #9350) (#9357) (Phil Quinn)
06efe87 Fix: Add meta element with charset attribute. (#9365) (H1Gdev)
1c6bc67 Fix: special EventEmitter keys leak information about other rules (#9328) (Teddy Katz)
38d0cb2 Fix: fix wrong code-path about try-for-in (fixes #8848) (#9348) (Toru Nagashima)
434d9e2 Fix: Invalid font-size property value issue. (#9341) (H1Gdev)

Documentation

cef6f8c Docs: remove line about removing rules from semver policy (#9367) (Teddy Katz)
458ca67 Docs: update architecture page (fixes #9337) (#9345) (Victor Hom)
d593e61 Docs: update eslint.org links to use https (#9358) (Teddy Katz)

Chores

b1372da Chore: remove sourceCode property from Linter (refs #9161) (#9363) (Teddy Katz)
a7668c2 Chore: Remove unnecessary slice from logging utility (#9343) (Gyandeep Singh)
2ff6fb6 Chore: remove unused arguments in codebase (#9340) (Teddy Katz)

ESLint v4.7.2 released

2017-09-21T00:00:00Z

Bug Fixes

4f87732 Fix: Revert setting node.parent early (fixes #9331) (#9336) (Teddy Katz)

ESLint v4.7.1 released

2017-09-18T00:00:00Z

Bug Fixes

08656db Fix: Handle nested disable directive correctly (fixes #9318) (#9322) (Gyandeep Singh)

ESLint v4.7.0 released

2017-09-15T00:00:00Z

Highlights

newline-per-chained-call supports autofix.
Processor plugins can now autofix code. To support autofix in processor plugins, developers can signal support by setting supportsAutofix: true and update the postprocess method to transform fix ranges in reported problems. This is explained fully in the Processors documentation.

Enhancements

1488b51 Update: run rules after node.parent is already set (fixes #9122) (#9283) (Teddy Katz)
ce1f084 Update: fix MemberExpression handling in no-extra-parens (fixes #9156) (jackyho112)
0c720a3 Update: allow autofixing when using processors (fixes #7510) (#9090) (Teddy Katz)
f12def6 Update: indent flatTernary option to handle return (fixes #9285) (#9296) (Teddy Katz)
2731f94 Update: make newline-per-chained-call fixable (#9149) (João Granado)
a32ec36 Update: refactor eslint-disable comment processing (#9216) (Teddy Katz)

Bug Fixes

e220687 Fix: remove autofix for var undef inits (fixes #9231) (#9288) (Victor Hom)
7685fed Fix: IIFE and arrow functions in no-invalid-this (fixes #9126) (#9258) (Toru Nagashima)
981f933 Fix: reuse the AST of source code object in verify (#9256) (Toru Nagashima)
51132d6 Fix: Formatters keep trailing ‘.’ if preceded by a space (fixes #9154) (#9247) (i-ron-y)
7ba46e6 Fix: shebang error in eslint-disable-new-line; add tests (fixes #9238) (#9240) (i-ron-y)

Documentation

4431d68 Docs: fix wrong config in max-len example. (#9309) (薛定谔的猫)
7d24dde Docs: Fix code snippet to refer to the correct option (#9313) (Ruben Tytgat)
002e199 Docs: fix no-restricted-globals wrong config. (#9305) (薛定谔的猫)
fcfe91a Docs: fix wrong config in id-length example. (#9303) (薛定谔的猫)
cd698ba Docs: move RuleTester documentation to Node.js API page (#9273) (Teddy Katz)
4ae7ad3 Docs: fix inaccuracy in npm run perf description (#9274) (Teddy Katz)
cad45bd Docs: improve documentation for rule contexts (#9272) (Teddy Katz)
c3231b3 Docs: Fix typo in array-bracket-newline.md (#9269) (宋文强)
82d8b73 Docs: Fix error in example code for sort-imports (fixes #8734) (#9245) (i-ron-y)
5566e94 Docs: Replace misleading CLA links (#9133) (#9232) (i-ron-y)

Dependency Upgrades

787b78b Upgrade: Espree v3.5.1 (fixes #9153) (#9314) (Brandon Mills)

abc8634 Build: re-run browserify when generating site (#9275) (Teddy Katz)

Chores

838df76 Chore: upgrade deps. (#9289) (薛定谔的猫)
61f1093 Chore: avoid monkeypatching Linter instances in RuleTester (#9276) (Teddy Katz)
28929cb Chore: remove Linter#reset (refs #9161) (#9268) (Teddy Katz)
2b1eba2 Chore: enable eslint-plugin/no-deprecated-context-methods (#9279) (Teddy Katz)
3b0c6fd Chore: remove extraneous linter properties (refs #9161) (#9267) (Teddy Katz)
88d5d4d Chore: remove undocumented Linter#markVariableAsUsed method (refs #9161) (#9266) (Teddy Katz)
09414cf Chore: remove internal Linter#getDeclaredVariables method (refs #9161) (#9264) (Teddy Katz)
f31f59d Chore: prefer smaller scope for variables in codebase (#9265) (Teddy Katz)
3693e4e Chore: remove undocumented Linter#getScope method (#9253) (Teddy Katz)
5d7eb81 Chore: refactor config hash caching in CLIEngine (#9260) (Teddy Katz)
1a76c4d Chore: remove SourceCode passthroughs from Linter.prototype (refs #9161) (#9263) (Teddy Katz)
40ae27b Chore: avoid relying on Linter#getScope/markVariableAsUsed in tests (#9252) (Teddy Katz)
b383d81 Chore: make executeOnFile a pure function in CLIEngine (#9262) (Teddy Katz)
5e0e579 Chore: avoid internal SourceCode methods in Linter tests (refs #9161) (#9223) (Teddy Katz)
adab827 Chore: remove unused eslint-disable comment (#9251) (Teddy Katz)
31e4ec8 Chore: use consistent names for apply-disable-directives in tests (#9246) (Teddy Katz)
8f6546c Chore: remove undocumented defaults() method (refs #9161) (#9237) (Teddy Katz)
583f0b8 Chore: avoid using globals in CLIEngine tests (#9242) (Teddy Katz)
c8bf687 Chore: upgrade eslint-plugin-eslint-plugin@1.0.0 (#9234) (薛定谔的猫)
3c41a05 Chore: always normalize rules to new API in rules.js (#9236) (Teddy Katz)
c5f4227 Chore: move logic for handling missing rules to rules.js (#9235) (Teddy Katz)
bf1e344 Chore: create report translators lazily (#9221) (Teddy Katz)
2eedc1f Chore: remove currentFilename prop from Linter instances (refs #9161) (#9219) (Teddy Katz)
c991630 Chore: remove ConfigOps.normalize in favor of ConfigOps.getRuleSeverity (#9224) (Teddy Katz)
171962a Chore: remove internal Linter#getAncestors helper (refs #9161) (#9222) (Teddy Katz)
a567499 Chore: avoid storing list of problems on Linter instance (refs #9161) (#9214) (Teddy Katz)
ed6d088 Chore: avoid relying on undocumented Linter#getFilename API in tests (#9218) (Teddy Katz)

ESLint v4.6.1 released

2017-09-03T00:00:00Z

Bug Fixes

cb74b87 Fix: avoid adding globals when an env is used with false (fixes #9202) (#9203) (Teddy Katz)

Documentation

f9b7544 Docs: Correct a typo in generator-star-spacing documentation (#9205) (Ethan Rutherford)

bdec46d Build: avoid process leak when generating website (#9217) (Teddy Katz)
e5c5e83 Build: Fixing issue with docs generation (Fixes #9199) (#9200) (Ilya Volodin)

ESLint v4.6.0 released

2017-09-01T00:00:00Z

Highlights

One new rule has been added: function-paren-newline
The generator-star-spacing rule is now configurable by function type.

Features

0e09973 New: function-paren-newline rule (fixes #6074) (#8102) (Teddy Katz)

Enhancements

6becf91 Update: add eslint version to error output. (fixes #9037) (#9071) (薛定谔的猫)
2db356b Update: no-unused-vars Improve message to include the allowed patterns (#9176) (Eli White)
8fbaf0a Update: Add configurability to generator-star-spacing (#8985) (Ethan Rutherford)

Bug Fixes

1bbac51 Fix: avoid breaking eslint-plugin-eslint-comments (fixes #9193) (#9196) (Teddy Katz)
3e8b70a Fix: off-by-one error in eslint-disable comment checking (#9195) (Teddy Katz)
af4ad60 Fix: Handle error when running init without npm (#9169) (Gabriel Aumala)
5ab0434 Fix: indent crash on sparse arrays with “off” option (fixes #9157) (#9166) (Teddy Katz)
d6e436f Fix: no-extra-parens reported some parenthesized IIFEs (fixes #9140) (#9158) (Teddy Katz)

Documentation

56dd769 Docs: fix link format in prefer-arrow-callback.md (#9198) (Vse Mozhet Byt)
73815f6 Docs: rewrite prefer-arrow-callback documentation (fixes #8950) (#9077) (Charles E. Morgan)
de6dccd Docs: add documentation for Linter methods (refs #6525) (#9151) (Teddy Katz)
ffa021e Docs: quotes rule - when does \n require backticks (#9135) (avimar)

e6b115c Build: Add an edit link to the rule docs’ metadata (#9049) (Jed Fox)

Chores

88a64cc Chore: Make parseJsonConfig() a pure function in Linter (#9186) (Teddy Katz)
0d3a854 Chore: avoid mutating report descriptors in report-translator (#9189) (Teddy Katz)
8ed779c Chore: remove currentScopes property from Linter instances (refs #9161) (#9187) (Teddy Katz)
4b94c6c Chore: make parse() a pure function in Linter (refs #9161) (#9183) (Teddy Katz)
1be5634 Chore: don’t make Linter a subclass of EventEmitter (refs #9161) (#9177) (Teddy Katz)
e95af9b Chore: don’t include internal test helpers in npm package (#9160) (Teddy Katz)
6fb32e1 Chore: avoid using private Linter APIs in astUtils tests (refs #9161) (#9173) (Teddy Katz)
2d90030 Chore: remove unused assignment. (#9182) (薛定谔的猫)
d672aef Chore: refactor reporting logic (refs #9161) (#9168) (Teddy Katz)
c147b97 Chore: Make SourceCodeFixer accept text instead of a SourceCode instance (#9178) (Teddy Katz)
f127423 Chore: avoid using private Linter APIs in Linter tests (refs #9161) (#9175) (Teddy Katz)
2334335 Chore: avoid using private Linter APIs in SourceCode tests (refs #9161) (#9174) (Teddy Katz)
2dc243a Chore: avoid using internal Linter APIs in RuleTester (refs #9161) (#9172) (Teddy Katz)
fcb7bb4 Chore: avoid unnecessarily complex forEach calls in no-extra-parens (#9159) (Teddy Katz)
60c5148 Chore: improve coverage in lib/*.js (#9130) (Teddy Katz)

ESLint v4.5.0 released

2017-08-18T00:00:00Z

Highlights

The indent rule can now be configured to ignore the indentation of specific types of syntax, using the ignoredNodes option. This can be useful if you disagree with some of the indentation choices made by the indent rule; instead of disabling the rule entirely when this happens, you can now configure it to avoid checking indentation for the specific cases that you want it to ignore.

Enhancements

decdd2c Update: allow arbitrary nodes to be ignored in indent (fixes #8594) (#9105) (Teddy Katz)
79062f3 Update: fix indentation of multiline new.target expressions (#9116) (Teddy Katz)
bd09cd5 Update: avoid requiring NaN spaces of indentation (fixes #9083) (#9085) (Teddy Katz)

Bug Fixes

a4f53ba Fix: Include files with no messages in junit results (#9093) (#9094) (Sean DuBois)
f8add8f Fix: don’t autofix with linter.verifyAndFix when fix: false is used (#9098) (Teddy Katz)

Documentation

6ef734a Docs: add missing word in processor documentation (#9106) (Teddy Katz)
77bcee4 Docs: update instructions for adding TSC members (#9086) (Teddy Katz)

Dependency Upgrades

d00e24f Upgrade: chalk to 2.x release (#9115) (Stephen Edgar)

Chores

1d6a9c0 Chore: enable eslint-plugin/test-case-shorthand-strings (#9067) (薛定谔的猫)
c93a853 Chore: Remove extra space in blogpost template (#9088) (Kai Cataldo)

ESLint v4.4.1 released

2017-08-07T00:00:00Z

Bug Fixes

ec93614 Fix: no-multi-spaces to avoid reporting consecutive tabs (fixes #9079) (#9087) (Teddy Katz)

ESLint v4.4.0 released

2017-08-05T00:00:00Z

Highlights

Initial support for ECMAScript 2018

Because ECMAScript 2018 is still under development, we are implementing features as they are finalized. This release includes the following:

Invalid escape sequences in tagged template literals

Enhancements

62911e4 Update: Add ImportDeclaration option to indent rule (#8955) (David Irvine)
7247b6c Update: handle indentation of custom destructuring syntax (fixes #8990) (#9027) (Teddy Katz)
3d020b9 Update: emit a warning for ecmaFeatures rather than throwing an error (#8974) (Teddy Katz)

Bug Fixes

b3e4598 Fix: clarify AST and don’t use node.start/node.end (fixes #8956) (#8984) (Toru Nagashima)
78a85e0 Fix: no-extra-parens incorrectly reports async function expressions (#9035) (薛定谔的猫)
c794f86 Fix: getter-return reporting method named ‘get’ (fixes #8919) (#9004) (薛定谔的猫)
5ab282f Fix: Print error message in bin/eslint.js (fixes #9011) (#9041) (Victor Hom)
cdb82f2 Fix: padding-line-between-statements crash on semicolons after blocks (#8748) (Alexander Madyankin)
0f97279 Fix: refactor no-multi-spaces to avoid regex backtracking (fixes #9001) (#9008) (Teddy Katz)
b74514d Fix: refactor RuleContext to not modify report locations (fixes #8980) (#8997) (Teddy Katz)
31d7fd2 Fix: inconsistent indent behavior on computed properties (fixes #8989) (#8999) (Teddy Katz)
3393894 Fix: avoid reporting the entire AST for missing rules (#8998) (Teddy Katz)
d2f8f9f Fix: include name of invalid config in validation messages (fixes #8963) (#8973) (Teddy Katz)

Documentation

5ae8458 Docs: fix typo in object-shorthand.md (#9066) (Jon Berry)
c3d5b39 Docs: clarify options descriptions (fixes #8875) (#9060) (Brandon Mailhiot)
37158c5 Docs: clarified behavior of globalReturn option (fixes #8953) (#9058) (Brandon Mailhiot)
c2f3553 Docs: Update example for MemberExpression option of indent (fixes #9056) (#9057) (Jeff)
d0f78ec Docs: update rule deprecation policy (fixes #8635) (#9033) (Teddy Katz)
50e3cf3 Docs: Update sort-keys doc to define natural ordering (fixes #9043) (#9045) (Karan Sharma)
66c1d43 Docs: Create SUPPORT.md (#9031) (Teddy Katz)

Dependency Upgrades

89196fd Upgrade: Espree to 3.5.0 (#9074) (Gyandeep Singh)
ad32697 Upgrade: js-yaml to 3.9.1 (refs #9011) (#9044) (Teddy Katz)
9b6c552 Upgrade: eslint-plugin-eslint-plugin@0.8.0 (#9012) (薛定谔的猫)

Chores

de75f9b Chore: enable object-curly-newline & object-property-newline.(fixes #9042) (#9068) (薛定谔的猫)
7ecfe6a Chore: enable eslint-plugin/test-case-property-ordering (#9040) (薛定谔的猫)
3141872 Chore: remove unnecessary eslint-disable comments in codebase (#9032) (Teddy Katz)
b3b95b8 Chore: enable additional rules on ESLint codebase (#9013) (Teddy Katz)
acbe86a Chore: disallow .substr and .substring in favor of .slice (#9010) (Teddy Katz)
d0536d6 Chore: Optimizes adding Linter methods (fixes #9000) (#9007) (Sean C Denison)
0a0401f Chore: fix spelling error. (#9003) (薛定谔的猫)
c3ee46b Chore: fix misleading comment in RuleTester (#8995) (Teddy Katz)

ESLint v4.3.0 released

2017-07-21T00:00:00Z

Enhancements

91dccdf Update: support more options in prefer-destructuring (#8796) (Victor Hom)
3bebcfd Update: Support generator yields in no constant condition (#8762) (Victor Hom)
e639358 Update: add question to confirm downgrade (fixes #8870) (#8911) (Toru Nagashima)
3c231fa Update: add enforceInMethodNames to no-underscore-dangle (fixes #7065) (#7234) (Gabriele Petronella)
128591f Update: prefer-numeric-literals warns Number.parseInt (fixes #8913) (#8929) (Kevin Partington)
fb8005d Update: no-restricted-globals custom error messages (fixes #8315) (#8932) (Kevin Partington)
1ea3723 Update: fix indentation of parenthesized MemberExpressions (fixes #8924) (#8928) (Teddy Katz)
9abc6f7 Update: fix BinaryExpression indentation edge case (fixes #8914) (#8930) (Teddy Katz)

Bug Fixes

96df8c9 Fix: Handle fixing objects containing comments (fixes #8484) (#8944) (Brian Schemp)
a5fd101 Fix: duplicated error message if a crash occurs (fixes #8964) (#8965) (Teddy Katz)
55bc35d Fix: Avoid shell mangling during eslint --init (#8936) (Anders Kaseorg)
597c217 Fix: confusing error if plugins from config is not an array (#8888) (Calvin Freitas)

Documentation

e39d41d Docs: Make peerDependencies package.json snippet valid JSON (#8971) (Sam Adams)
f8d122c Docs: trailing commas not allowed in json (#8969) (Scott Fletcher)
601039d Docs: fix badge in eslint-config-eslint readme (#8954) (Teddy Katz)
846f8b1 Docs: Clarified that core PRs require issue in maintainer guide (#8927) (Kevin Partington)
0e90453 Docs: Fixing broken cyclomatic complexity link (fixes #8396) (#8937) (Chris Bargren)
3c1dd6d Docs: add description of no-sync allowAtRootLevel option (fixes #8902) (#8906) (Teddy Katz)
45f8cd9 Docs: fix verifyAndFix result property name (#8903) (Tino Vyatkin)
1a89e1c Docs: Fix always-multiline example in multiline-ternary docs (#8904) (Nathan Woltman)

Chores

d09288a Chore: Use output: null to assert that a test case is not autofixed. (#8960) (薛定谔的猫)
10c3d78 Chore: fix misleading indent test (#8925) (Teddy Katz)
a747b6f Chore: make minor improvements to indent internals (#8947) (Teddy Katz)
a8a8350 Chore: improve performance of indent rule (#8905) (Teddy Katz)
764b2a9 Chore: update header info in indent (#8926) (Teddy Katz)
933a9cf Chore: add a fuzzer to detect bugs in core rules (#8422) (Teddy Katz)

ESLint v4.2.0 released

2017-07-08T00:00:00Z

Highlights

linter.verifyAndFix can now accept a filter function for fixes

When using the Node.js API to autofix code, it’s sometimes undesirable to autofix every problem at once. For example, a user might want to avoid fixing problems reported by particular rule, or a tool might want to only fix one problem at a time. You can now pass an object like { fix: message => /* ... */ } to the third argument of linter.verifyAndFix, or to the CLIEngine constructor. If the fix function returns true, a fix is applied – otherwise, a fix is not applied. eslint-nibble uses this feature to autofix individual rules, or only autofix errors rather than warnings.

Also see: documentation
The getter-return rule has been added.
The no-sync rule now has a boolean allowAtRootLevel option to allow sync function calls at the top level of a file.
The multiline-ternary rule now has an always-multiline option.

Features

c693be5 New: Allow passing a function as fix option (fixes #8039) (#8730) (Ian VanSchooten)
8698a92 New: getter-return rule (fixes #8449) (#8460) (薛定谔的猫)

Enhancements

e0f0101 Update: fix indentation of nested function parameters (fixes #8892) (#8900) (Teddy Katz)
975dacf Update: fix indentation of EmptyStatements (fixes #8882) (#8885) (Teddy Katz)
3767cda Update: add no-sync option to allow at root level (fixes #7985) (#8859) (Victor Hom)
1f5bfc2 Update: Add always-multiline option to multiline-ternary (fixes #8770) (#8841) (Nathan Woltman)
676af9e Update: fix indentation of JSXExpressionContainer contents (fixes #8832) (#8850) (Teddy Katz)
85c9327 Update: fix parenthesized CallExpression indentation (fixes #8790) (#8802) (Teddy Katz)
be8d354 Update: simplify variable declarator indent handling (fixes #8785) (#8801) (Teddy Katz)

Bug Fixes

11ffe6b Fix: no-regex-spaces rule incorrectly fixes quantified spaces (#8773) (Keri Warr)
931a9f1 Fix: indent false positive with multi-line await expression (#8837) (薛定谔的猫)
f00854e Fix: --quiet no longer fixes warnings (fixes #8675) (#8858) (Kevin Partington)
22116f2 Fix: correct comma-dangle JSON schema (#8864) (Evgeny Poberezkin)
5c3ac8e Fix: arrow-parens fixer gets tripped up with trailing comma in args (#8838) (薛定谔的猫)
9417818 Fix: no-debugger autofixer produced invalid syntax (#8806) (Teddy Katz)
eac06f2 Fix: no-extra-parens false positives for variables called “let” (#8808) (Teddy Katz)
616587f Fix: dot-notation autofix produces syntax errors for object called “let” (#8807) (Teddy Katz)
a53ef7e Fix: don’t require a third argument in linter.verifyAndFix (fixes #8805) (#8809) (Teddy Katz)

Documentation

7c8de92 Docs: Clarified PR guidelines in maintainer guide (#8876) (Kevin Partington)
d1fc408 Docs: Update CLA link in Contributing docs (#8883) (Calvin Freitas)
1ce553d Docs: Fix wording of minProperties in object-curly-newline (fixes #8874) (#8878) (solmsted)
8796d55 Docs: add missing item to 4.0 migration guide table of contents (#8835) (薛定谔的猫)
ce969f9 Docs: add guidelines for patch release communication (fixes #7277) (#8823) (Teddy Katz)
5c83c99 Docs: Clarify arrow function parens in no-extra-parens (fixes #8741) (#8822) (Kevin Partington)
84d921d Docs: Added note about Node/CJS scoping to no-redeclare (fixes #8814) (#8820) (Kevin Partington)
5ad8b70 Docs: add minor formatting improvement to paragraph about parsers (#8816) (Teddy Katz)

88ed041 Build: Turnoff CI branch build (fixes #8804) (#8873) (Gyandeep Singh)
c4f2e29 Build: fix race condition in demo (#8827) (Teddy Katz)

Chores

9f95a3e Chore: remove unused helper method from indent (#8901) (Teddy Katz)
72f22eb Chore: replace is-my-json-valid with Ajv (#8852) (Gajus Kuizinas)
b678535 Chore: Add collapsible block for config in ISSUE_TEMPLATE (#8872) (Gyandeep Singh)
330dd58 Chore: fix title of linter test suite (#8861) (Teddy Katz)
60099ed Chore: enable for-direction rule on ESLint codebase (#8853) (薛定谔的猫)
e0d1a84 Chore: upgrade eslint-plugin-eslint-plugin & eslint-plugin-node (#8856) (薛定谔的猫)
0780d86 Chore: remove identical tests (#8851) (Teddy Katz)

ESLint v4.1.1 released

2017-06-25T00:00:00Z

Bug Fixes

f307aa0 Fix: ensure configs from a plugin are cached separately (fixes #8792) (#8798) (Teddy Katz)
0d041e7 Fix: avoid crashing when using baseConfig with extends (fixes #8791) (#8797) (Teddy Katz)

Documentation

8b48ae8 Docs: Add doc on parser services (fixes #8390) (#8795) (Victor Hom)

Chores

03213bb Chore: improve comment explanation of indent internal functions (#8800) (Teddy Katz)
d2e88ed Chore: Fix misleading comment in ConfigCache.js (#8799) (Teddy Katz)

ESLint v4.1.0 released

2017-06-23T00:00:00Z

Highlights

Glob-based configuration

Previously, it was not possible to use different ESLint configurations for two different files in the same directory. For example, projects that place test files in the same directory as the corresponding source files were unable to use different ESLint configurations for the test files. Adding support for this has been one of our most requested features.

This release adds support for glob-based configuration via an overrides key in a config file, which can be used to apply a configuration to specific globs. For example, you can now enable the mocha environment on only test files, with the following config:

module.exports = {
  rules: {
    // ... the rest of your config (applied to all files)
  },
  overrides: [
    {
      files: ["foo/**/*.spec.js", "bar/**/*.spec.js"],

      // Override config (only applied to files that match the given globs)
      env: { mocha: true }
    }
  ]
};

For full details, see the documentation.

Ignoring files from `package.json`

It’s common for users to use an .eslintignore file to indicate the files that they would like ESLint to ignore. However, if you don’t want to add additional files to your project root, you can now ignore files by setting the eslintIgnore property in a package.json file to a list of globs:

{
  "eslintIgnore": [
    "build/**/*.js",
    "dist/**/*.js"
  ]
}

Also see: documentation

Applying multiple autofixes simultaneously

When writing a custom rule that can automatically fix problems, one sometimes needs to apply multiple fixes atomically. For example, if an autofix adds parentheses around a piece of source code, adding only one parenthesis will result in a syntax error. Since ESLint does not guarantee that it will be able to apply every fix without conflicts, it was previously not possible to atomically apply multiple fixes (without using confusing workarounds).

Starting in 4.1.0, if you return an array of fixes from a fix function rather than a single fix, all the fixes in the array will be applied atomically.

context.report({
  node,
  message,
  fix(fixer) {
    return [
      fixer.insertTextBefore(node, "("),
      fixer.insertTextAfter(node, ")")
    ]
  }
})

Also see: Autofixing docs

Applying autofixes from `Linter`

When using ESLint’s Node.js API, it was previously not possible to get automatic fix information for a given source code and configuration when using eslint.Linter. Instead, one had to use eslint.CLIEngine, which is more general and less easy to use.

Starting in 4.1.0, you can now use Linter#verifyAndFix to get autofixing information when using Linter. (You should still use CLIEngine if you need to do more general operations, such as reading config files from the filesystem.)

For more details, see the documentation.

Other highlights

An enforceForArrowConditionals option has been added to the no-extra-parens rule.
An ignoreComments option has been added to the no-trailing-spaces rule.

Full Changelog

Features

a21dd32c New: Add overrides/files options for glob-based config (fixes #3611) (#8081) (Sylvan Mably)
5f81a68a New: Add eslintIgnore support to package.json (fixes #8458) (#8690) (Victor Hom)

Enhancements

291a7830 Update: enforceForArrowConditionals to no-extra-parens (fixes #6196) (#8439) (Evilebot Tnawi)
879688ce Update: Add ignoreComments option to no-trailing-spaces (#8061) (Jake Roussel)
98512881 Update: fix indent errors on multiline destructure (fixes #8729) (#8756) (Victor Hom)
673a58bc Update: support multiple fixes in a report (fixes #7348) (#8101) (Toru Nagashima)
b5a70b4e Update: fix multiline binary operator/parentheses indentation (#8719) (Teddy Katz)
ab8b0167 Update: fix MemberExpression indentation with “off” option (fixes #8721) (#8724) (Teddy Katz)
eb5d12c1 Update: Add Fixer method to Linter API (#8631) (Gyandeep Singh)

Bug Fixes

7a1bc389 Fix: don’t pass default parserOptions to custom parsers (fixes #8744) (#8745) (Teddy Katz)
b7cc1e6f Fix: Space-infix-ops should ignore type annotations in TypeScript (#8341) (Reyad Attiyat)
46e73eea Fix: eslint --init installs wrong dependencies of popular styles (fixes #7338) (#8713) (Toru Nagashima)

Documentation

e8f1362a Docs: Remove wrong descriptions in padded-block rule (#8783) (Plusb Preco)
3608f06c Docs: Increase visibility of code of conduct (fixes #8758) (#8764) (Kai Cataldo)
3419f644 Docs: describe how to use formatters on the formatter demo page (#8754) (Teddy Katz)

Chores

b58ae2e6 Chore: Only instantiate fileEntryCache when cache flage set (perf) (#8763) (Gyandeep Singh)
c5b40528 Chore: enable computed-property-spacing on ESLint codebase (#8760) (Teddy Katz)
a3ff8f21 Chore: combine tests in tests/lib/eslint.js and tests/lib/linter.js (#8746) (Teddy Katz)
a82361b6 Chore: Prevent package-lock.json files from being created (fixes #8742) (#8747) (Teddy Katz)
26a2daab Chore: Cache fs reads in ignored-paths (fixes #8363) (#8706) (Victor Hom)

ESLint v4.0.0 released

2017-06-11T00:00:00Z

Highlights

There are several breaking changes in 4.0.0. We’ve created a migration guide to explain the breaking changes and describe how to upgrade.
Seven new rules have been added:
Two rules are now autofixable with the --fix flag:
- no-debugger
- no-confusing-arrow
Three rules have been deprecated in favor of the new padding-line-between-statements rule:
Three new utility methods have been added to the SourceCode API, and SourceCode#getComments has been deprecated.
A new option has been added to the object-curly-newline rule.

Changes since v4.0.0-rc.0:

Enhancements

34c4020 Update: Add support for parens on left side for-loops (fixes: #8393) (#8679) (Victor Hom)

Bug Fixes

3da7b5e Fix: Semi-Style only check for comments when tokens exist (fixes #8696) (#8697) (Reyad Attiyat)
3cfe9ee Fix: Add space between async and param on fix (fixes #8682) (#8693) (Reyad Attiyat)

Documentation

735cd09 Docs: Correct the comment in an example for no-mixed-requires (#8686) (Fangzhou Li)

Chores

4aefb49 Chore: avoid using deprecated rules on ESLint codebase (#8708) (Teddy Katz)
389feba Chore: upgrade deps. (#8684) (薛定谔的猫)
c702858 Chore: enable no-multiple-empty-lines on ESLint codebase (#8694) (Teddy Katz)
026f048 Chore: remove dead code from prefer-const (#8683) (Teddy Katz)

ESLint v4.0.0-rc.0 released

2017-06-02T00:00:00Z

Highlights

If you’re upgrading from 3.x, see the migration guide.
One new rule was added in this release:
- array-element-newline
One rule gained support for --fix:
- no-debugger

Features

7ebd9d6f New: array-element-newline rule (fixes #6075) (#8375) (Jan Peer Stöcklmair)

Enhancements

0058b0f8 Update: add --fix to no-debugger (#8660) (薛定谔的猫)
c4ac969c Update: fix parenthesized ternary expression indentation (fixes #8637) (#8649) (Teddy Katz)

Bug Fixes

95248336 Fix: Don’t check object destructing in integer property (fixes #8654) (#8657) (flowmemo)
d0e9fd2d Fix: Config merge to correctly account for extends (fixes #8193) (#8636) (Gyandeep Singh)

Documentation

b4daa225 Docs: Note to --fix option for strict rule (#8680) (Vitaliy Potapov)
b0c83bd1 Docs: suggest pushing new commits to a PR instead of amending (#8632) (Teddy Katz)
705d88f7 Docs: Update CLA link on Pull Requests page (#8642) (Teddy Katz)
794d4d6c Docs: missing paren on readme (#8640) (Dan Beam)
936bc174 Docs: Add missing documentation for scoped modules in sharable config developer-guide (#8610) (Jonathan Samines)

c9b980ce Build: Add Node 8 on travis (#8669) (Gyandeep Singh)
4f2f9fcb Build: update license checker to allow LGPL (fixes #8647) (#8652) (Teddy Katz)

Chores

4df33e7c Chore: check for root:true in project sooner (fixes #8561) (#8638) (Victor Hom)
f62cff66 Chore: Remove dependency to user-home (fixes #8604) (#8629) (Pavol Madar)

ESLint v4.0.0-beta.0 released

2017-05-19T00:00:00Z

Highlights

If you’re upgrading from 3.x, see the migration guide.
Four new rules have been added in this release:
Previously, ESLint’s Node.js API exposed a mutable eslint.linter object which could be used to lint text. This could cause problems if two unrelated modules were using eslint.linter at the same time, because they might both mutate it and interfere with each other. To resolve this, ESLint now exposes an eslint.Linter constructor, which can be used to create mutable linter instances. We recommend that integrations switch to using eslint.Linter rather than eslint.linter.
Three rules have been deprecated in favor of the new padding-line-between-statements rule:

Breaking Changes

3ec436ee Breaking: New Linter API (fixes #8454) (#8465) (Gyandeep Singh)

Features

2f7015b6 New: semi-style rule (fixes #8169) (#8542) (Toru Nagashima)
a93a2f95 New: padding-line-between-statements rule (fixes #7356) (#8099) (Toru Nagashima)
0ef09ea0 New: for-direction rule (fixes #8387) (#8519) (薛定谔的猫)
482d5720 New: switch-colon-spacing rule (fixes #7981) (#8540) (Toru Nagashima)

Enhancements

3418479a Update: improve indent of flatTernaryExpressions (fixes #8481) (#8587) (Toru Nagashima)
268d52ef Update: Use sane defaults for JSX indentation (fixes #8425) (#8593) (Teddy Katz)
afa35c68 Update: check allman-style classes correctly in indent (fixes #8493) (#8569) (Teddy Katz)
456f519b Update: make indent MemberExpression handling more robust (fixes #8552) (#8554) (Teddy Katz)

Bug Fixes

eb14584a Fix: no-unneeded-ternary change code behavior after fix (fixes #8507) (#8624) (Jan Peer Stöcklmair)
3fc9653a Fix: Call expression consistency in variable declaration (fixes #8607) (#8619) (Reyad Attiyat)
a73e6c09 Fix: Fix failing uknown node test since #8569 indents class bodies (#8588) (Reyad Attiyat)
c6c639d6 Fix: Ignore unknown nodes for Indent rule (fixes #8440) (#8504) (Reyad Attiyat)
df17bc87 Fix: object-shorthand crash on some computed keys (fixes #8576) (#8577) (Teddy Katz)
de0b4ad7 Fix: Indent Ignore Variable Declaration init operator (fixes #8546) (#8563) (Reyad Attiyat)
927ca0dc Fix: invalid syntax from prefer-arrow-callback autofixer (fixes #8541) (#8555) (Teddy Katz)
873310e5 Fix: run no-unexpected-multiline only if needed (fixes #8550) (#8551) (Ruben Bridgewater)
833a0cad Fix: confusing RuleTester error message when options is not an array (#8557) (Teddy Katz)

Documentation

5b6093ef Docs: Remove .eslintignore reference to transpiled file filtering (#8622) (Alex Summer)
11493781 Docs: Rephrase in about section (#8609) (Sudarsan G P)

Chores

729bbcdb Chore: Fix lgtm alerts. (#8611) (Max Schaefer)
d21f5283 Chore: make shelljs a devDependency instead of a dependency (#8608) (Teddy Katz)
23401626 Chore: remove strip-bom dependency (refs #8603) (#8606) (Teddy Katz)
25db3d22 Chore: avoid skipping test for env overrides (refs #8291) (#8556) (Teddy Katz)

ESLint v4.0.0-alpha.2 released

2017-05-05T00:00:00Z

Highlights

ESLint will now validate .eslintrc.* files for unknown properties

Breaking Changes

734846b Breaking: validate eslintrc properties (fixes #8213) (#8295) (alberto)

Enhancements

74ab344 Update: check allman-style blocks correctly in indent rule (fixes #8493) (#8499) (Teddy Katz)
f6256d4 Update: no-extend-native checks global scope refs only (fixes #8461) (#8528) (Kevin Partington)
99c56d5 Update: handle multiline parents consistently in indent (fixes #8455) (#8498) (Teddy Katz)
cf940c6 Update: indent from tokens in import statements (fixes #8438) (#8466) (Teddy Katz)
d49acc3 Update: fix no-self-compare false negative on non-literals (fixes #7677) (#8492) (Teddy Katz)

Bug Fixes

0a9a90f Fix: max-len doesn’t allow comments longer than code (#8532) (Ken Gregory)
aaa1a81 Fix: avoid creating extra whitespace in brace-style fixer (fixes #7621) (#8491) (Teddy Katz)

Documentation

b463045 Docs: add typescript-eslint-parser (#8388) (#8534) (薛定谔的猫)
e52d998 Docs: Configuring Cascading and Hierarchy example correction (#8512) (Cheong Yip)
e135aa5 Docs: Correct code of conduct link on Readme.md (#8517) (Zander Mackie)
9c3da77 Docs: list another related rule in no-undefined (#8467) (Ethan)
f987814 Docs: Update CHANGELOG.md for v4.0.0-alpha.1 release (#8488) (Kai Cataldo)

Dependency Upgrades

6a333ff Upgrade: espree@^3.4.2 (#8526) (Kevin Partington)

Chores

025e97a Chore: delete duplicated test. (#8527) (薛定谔的猫)
37e3ba1 Chore: Add license report and scan status (#8503) (Kevin Wang)
afbea78 Chore: don’t pull default options from eslint:recommended (fixes #8374) (#8381) (Teddy Katz)

ESLint v4.0.0-alpha.1 released

2017-04-21T00:00:00Z

Highlights

The array-callback-return rule was added to eslint:recommended in the last prerelease, but it has been removed from eslint:recommended in this prerelease due to false positives that would occur when using methods in a few popular libraries. As a result, this rule will not be in eslint:recommended for 4.0.0.
Three new utility methods have been added to the SourceCode API, and SourceCode#getComments has been deprecated.
One new rule has been added: array-bracket-newline.
The no-confusing-arrow rule can now be autofixed.
The object-curly-newline rule has a new option.

Breaking Changes

fac53890 Breaking: Remove array-callback-return from recommended (fixes #8428) (#8433) (Kai Cataldo)

Features

7bc6fe0a New: array-bracket-newline rule (#8314) (Jan Peer Stöcklmair)

Enhancements

b337738f Update: Add consistent option to object-curly-newline (fixes #6488) (#7720) (Evilebot Tnawi)
53fefb3b Update: add fix for no-confusing-arrow (#8347) (Mordy Tikotzky)
735d02d5 Update: Deprecate sourceCode.getComments() (fixes #8408) (#8434) (Kai Cataldo)
ac39e3b0 Update: no-unexpected-multiline to flag confusing division (fixes #8469) (#8475) (Teddy Katz)
9f540fd2 Update: no-unused-vars false negative about destructuring (fixes #8442) (#8459) (Toru Nagashima)

Bug Fixes

e35107f0 Fix: indent crash on arrow functions without parens at start of line (#8477) (Teddy Katz)

Documentation

b0dadfe3 Docs: Update comments section of Migrating to v4.0.0 (#8486) (Kai Cataldo)
973adeb6 Docs: State that functions option only applies in ES2017 (fixes #7809) (#8468) (Thenaesh Elango)
741ed393 Docs: Clarify how to run local ESLint installation (#8463) (Kai Cataldo)
48700fc8 Docs: Remove extra header line from LICENSE (#8448) (Teddy Katz)
0c2a386e Docs: clarify new indent behavior with MemberExpressions (#8432) (Teddy Katz)
446b8876 Docs: update space-before-function-paren docs for 4.0 (fixes #8430) (#8431) (Teddy Katz)

Dependency Upgrades

288c96c1 Upgrade: dependencies (#8304) (alberto)

1c7efbd2 Build: changelog update for 4.0.0-alpha.1 (Kai Cataldo)

Chores

10a1a2d7 Chore: Do not use cache when testing (#8464) (Kai Cataldo)
161ee4ea Chore: avoid cloning comments array in TokenStore (#8436) (Teddy Katz)

ESLint v4.0.0-alpha.0 released

2017-04-07T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Installing

Since this is a pre-release version, you will not automatically be upgraded by npm. You must specify the next tag when installing:

npm i eslint@next --save-dev

You can also specify the version directly:

npm i eslint@4.0.0-alpha.0 --save-dev

Migration Guide

As there are a lot of changes, we’ve created a migration guide describing the changes in great detail along with the steps you should take to address them. Not all ESLint users will be affected by the changes, however, the changes are big enough that we recommend everyone read the migration thoroughly.

New Rules

There is one new rule in this release:

no-buffer-constructor

Breaking Changes

f5a7e42 Breaking: log number of fixable problems (fixes #7364) (#8324) (alberto)
cc53481 Breaking: rewrite indent (fixes #1801, #3737, #3845, #6007, …16 more) (#7618) (Teddy Katz)
867dd2e Breaking: Calculate leading/trailing comments in core (fixes #6724) (#7516) (Kai Cataldo)
66af53e Breaking: Traverse into type annotations (fixes #7129) (#8365) (Kai Cataldo)
e395919 Breaking: Resolve patterns from .eslintignore directory (fixes #6759) (#7678) (Ian VanSchooten)
c778676 Breaking: convert RuleTester to ES6 class (refs #8231) (#8263) (Teddy Katz)
6f7757e Breaking: convert SourceCode to ES6 class (refs #8231) (#8264) (Teddy Katz)
9a9d916 Breaking: update eslint:recommended for 4.0.0 (fixes #8236) (#8372) (Teddy Katz)
b0c63f0 Breaking: infer endLine and endColumn from a reported node (fixes #8004) (#8234) (Teddy Katz)
40b8c69 Breaking: no-multi-spaces check around inline comments (fixes #7693) (#7696) (Kai Cataldo)
034a575 Breaking: convert CLIEngine to ES6 class (refs #8231) (#8262) (Teddy Katz)
7dd890d Breaking: tweak space-before-function-paren default option (fixes #8267) (#8285) (Teddy Katz)
0e0dd27 Breaking: Remove ecmaFeatures from eslint:recommended (#8239) (alberto)
2fa7502 Breaking: disallow scoped plugin references without scope (fixes #6362) (#8233) (Teddy Katz)
e232464 Breaking: change defaults for padded-blocks (fixes #7879) (#8134) (alberto)

Features

86cf3e4 New: no-buffer-constructor rule (fixes #5614) (#8413) (Teddy Katz)

Enhancements

8394e48 Update: add deprecated indent-legacy rule as v3.x indent rule snapshot (#8286) (Teddy Katz)
f560c06 Update: fix space-unary-ops behavior with postfix UpdateExpressions (#8391) (Teddy Katz)

Bug Fixes

2754141 Fix: more autofix token-combining bugs (#8394) (Teddy Katz)
3c87e85 Fix: no-multi-spaces false positive with irregular indent whitespace (#8412) (Teddy Katz)
936af66 Fix: no-multiple-empty-lines crash on space after last \n (fixes #8401) (#8402) (Teddy Katz)

Documentation

950874f Docs: add 4.0.0 migration guide (fixes #8306) (#8313) (Teddy Katz)
de9f1a0 Docs: ES6 syntax vs globals configuration (fixes #7984) (#8350) (Zander Mackie)

Chores

769b121 Chore: Fix indentation errors in indent-legacy (#8424) (Kai Cataldo)
8842d7e Chore: fix comment spacing in tests (#8405) (Teddy Katz)
4673f6e Chore: Switch to eslint-scope from escope (#8280) (Corbin Uselton)

ESLint v3.19.0 released

2017-03-31T00:00:00Z

Highlights

Building on the release of AST selectors in v3.18.0, no-restricted-syntax now supports custom error messages:

{
    "rules": {
        "no-restricted-syntax": [
            "error",
            {
                "selector": "CallExpression[callee.name='setTimeout'][arguments.length!=2]",
                "message": "setTimeout must always be invoked with two arguments."
            }
        ]
    }
}

Autofix is now more reliable thanks to nine individual fixes in this release.

Enhancements

91baed4 Update: allow custom messages in no-restricted-syntax (fixes #8298) (#8357) (Vitor Balocco)

Bug Fixes

e09132f Fix: no-extra-parens false positive with exports and object literals (#8359) (Teddy Katz)
35c93e6 Fix: prevent space-before-function-paren from checking type annotations (#8349) (Teddy Katz)
3342e9f Fix: don’t modify operator precedence in operator-assignment autofixer (#8358) (Teddy Katz)
155424c Fix: ignore empty path in patterns (fixes #8362) (#8364) (alberto)
27616a8 Fix: prefer-const false positive with object spread (fixes #8187) (#8297) (Vitor Balocco)
1b1046b Fix: don’t classify plugins that throw errors as “missing” (fixes #6874) (#8323) (Teddy Katz)
29f4ba5 Fix: no-useless-computed-key invalid autofix for getters and setters (#8335) (Teddy Katz)
0541eaf Fix: no-implicit-coercion invalid autofix with consecutive identifiers (#8340) (Teddy Katz)
41b9786 Fix: no-extra-parens false positive with objects following arrows (#8339) (Teddy Katz)
3146167 Fix: eslint.verify should not mutate config argument (fixes #8329) (#8334) (alberto)
927de90 Fix: dot-notation autofix produces invalid syntax for integer properties (#8332) (Teddy Katz)
a9d1bea Fix: comma-style autofix produces errors on parenthesized elements (#8331) (Teddy Katz)
d52173f Fix: don’t generate invalid options in config-rule (#8326) (Teddy Katz)
6eda3b5 Fix: no-extra-parens invalid autofix in for-of statements (#8337) (Teddy Katz)
6c819d8 Fix: dot-notation autofix produces errors on parenthesized computed keys (#8330) (Teddy Katz)
2d883d7 Fix: object-shorthand autofix produces errors on parenthesized functions (#8328) (Teddy Katz)
cd9b774 Fix: quotes false positive with backtick option in method names (#8327) (Teddy Katz)
d064ba2 Fix: no-else-return false positive for ifs in single-statement position (#8338) (Teddy Katz)
2f144ca Fix: operator-assignment autofix errors with parentheses (fixes #8293) (#8294) (Teddy Katz)
ddc6350 Fix: no-param-reassign false positive on destructuring (fixes #8279) (#8281) (Teddy Katz)

Documentation

f88375f Docs: clarify that no-unsafe-negation is in eslint:recommended (#8371) (Teddy Katz)
02f0d27 Docs: Add soda0289 to Development Team (#8367) (Kai Cataldo)
8569a90 Docs: add note about git’s linebreak handling to linebreak-style docs (#8361) (Teddy Katz)
602e9c2 Docs: fix incorrect selector examples (#8278) (Teddy Katz)

Dependency Upgrades

79a97cb Upgrade: devDependencies (#8303) (alberto)
e4da200 Upgrade: Mocha to 3.2.0 (#8299) (Ilya Volodin)

Chores

5878593 Chore: fix invalid syntax in no-param-reassign test (#8360) (Teddy Katz)
6a718ba Chore: enable max-statements-per-line on ESLint codebase (#8321) (Teddy Katz)
614b62e Chore: update sinon calls to deprecated API. (#8310) (alberto)
0491572 Chore: use precalculated counts in codeframe formatter (#8296) (Vitor Balocco)
8733e6a Chore: Fix incorrect error location properties in tests (#8307) (alberto)
c4ffb49 Chore: Fix typos in test option assertions (#8305) (Teddy Katz)
7521cd5 Chore: update token logic in rules to use ast-utils (#8288) (Teddy Katz)
9b509ce Chore: refactor space-before-function-paren rule (#8284) (Teddy Katz)
f8176b3 Chore: improve test coverage for node-event-generator (#8287) (Teddy Katz)

ESLint v3.18.0 released

2017-03-17T00:00:00Z

Highlights

This release adds support for AST selectors. AST selectors can describe syntax patterns very precisely, using a similar syntax to CSS selectors. Selectors can be used to:

simplify the implementation of custom rules.
disallow particular syntax patterns in a codebase using the no-restricted-syntax rule.

For example, suppose you want to disallow calls to Mocha’s xdescribe function in your codebase. Previously, it was not possible to do this without writing a custom rule. However, now you can configure the no-restricted-syntax rule with a selector:

{
  "rules": {
    "no-restricted-syntax": [
      "error",
      "CallExpression[callee.name='xdescribe']"
    ]
  }
}

Selectors can give you a lot of control over specific patterns in your code, without needing to write a custom rule for each pattern.

For more details, see the selector documentation.

Features

1b678a6 New: allow rules to listen for AST selectors (fixes #5407) (#7833) (Teddy Katz)

Enhancements

23eca51 Update: Add allowTaggedTemplates to no-unused-expressions (fixes #7632) (#8253) (Kevin Partington)
7f8afe6 Update: no-extra-parens overlooked spread and superClass (fixes #8175) (#8209) (Toru Nagashima)

Bug Fixes

85f74ca Fix: broken code path of direct nested loops (fixes #8248) (#8274) (Toru Nagashima)
a61c359 Fix: Ignore hidden folders when resolving globs (fixes #8259) (#8270) (Ian VanSchooten)
0c0fc31 Fix: false positive of no-extra-parens about spread and sequense (#8275) (Toru Nagashima)
47c3171 Fix: typo in console.error (#8258) (Jan Peer Stöcklmair)
13eead9 Fix: sort-vars crash on mixed destructuring declarations (#8245) (Teddy Katz)
133f489 Fix: func-name-matching crash on destructuring assignment to functions (#8247) (Teddy Katz)
a34b9c4 Fix: func-name-matching crash on non-string literal computed keys (#8246) (Teddy Katz)
5b5c236 Fix: wrong comment when module not found in config (fixes #8192) (#8196) (alberto)

Documentation

e104973 Docs: remove self-reference in no-restricted-syntax docs (#8277) (Vitor Balocco)
7276e6d Docs: remove unneeded semicolons in arrow-parens.md (#8249) (Dmitry Gershun)
df12137 Docs: fix typos (#8235) (Gyandeep Singh)
ce6ff56 Docs: set recommended true for no-global-assign (fixes #8215) (#8218) (BinYi LIU)

Dependency Upgrades

f9ede3f Upgrade: doctrine to 2.0.0 (#8269) (alberto)
8c40a25 Upgrade: update concat-stream to 1.5.2 (#8228) (Samuel)
149c055 Upgrade: mock-fs to v4.2.0 (fixes #8194) (#8243) (Teddy Katz)

a83bff9 Build: remove unneeded json config in demo (fixes #8237) (#8242) (alberto)

Chores

6f05546 Chore: convert StubModuleResolver in config tests to ES6 class (#8265) (Teddy Katz)
63ca0c5 Chore: use precalculated counts in stylish formatter (#8251) (alberto)
e74ed6d Chore: convert Traverser to ES6 class (refs #7849) (#8232) (Teddy Katz)
b5e9788 Chore: rename no-extra-parens methods (#8225) (Vitor Balocco)

ESLint v3.17.1 released

2017-03-06T00:00:00Z

Bug Fixes

f713f11 Fix: nonblock-statement-body-position multiline error (fixes #8202) (#8203) (Teddy Katz)
41e3d9c Fix: operator-assignment with parenthesized expression (fixes #8190) (#8197) (alberto)

f8c8e6e Build: change mock-fs path without SSH (fixes #8207) (#8208) (Toru Nagashima)

Chores

5e3bca7 Chore: add eslint-plugin-eslint-plugin (#8198) (Teddy Katz)
580da36 Chore: add missing output property to tests (#8195) (alberto)

ESLint v3.17.0 released

2017-03-03T00:00:00Z

Highlights

Two new rules were added:

Two new methods were added to the SourceCode API for rules:

getLocFromIndex and getIndexFromLoc

Two enhancements were made to the RuleTester utility:

Error message assertions can now be regular expressions.
output for a test case can be set to null to assert that the case is not autofixed.

Features

dad20ad New: add SourceCode#getLocFromIndex and #getIndexFromLoc (fixes #8073) (#8158) (Teddy Katz)
20daea5 New: no-compare-neg-zero rule (#8091) (薛定谔的猫)
287e882 New: nonblock-statement-body-position rule (fixes #6067) (#8108) (Teddy Katz)
7ff42e8 New: Allow regexes in RuleTester (fixes #7837) (#8115) (Daniel Lo Nigro)

Enhancements

4fdf6d7 Update: deprecate applyDefaultPatterns in line-comment-position (#8183) (alberto)
bf4d8cf Update: ignore eslint comments in lines-arount-comment (fixes #4345) (#8155) (alberto)
18a519f Update: let RuleTester cases assert that no autofix occurs (fixes #8157) (#8163) (Teddy Katz)
ca1694b Update: ignore negative ranges in fixes (#8133) (alberto)
da8e8af Update: include function name in report message if possible (fixes #7260) (#8058) (Dieter Luypaert)

Bug Fixes

25e5817 Fix: Don’t autofix + +a to ++a in space-unary-ops (#8176) (Alan Pierce)
d02bd11 Fix: padded-blocks autofix problems with comments (#8149) (alberto)
4d35a81 Fix: Add a utility to avoid autofix conflicts (fixes #7928, fixes #8026) (#8067) (Alan Pierce)
1ee5c27 Fix: Make RuleTester handle empty-string cases gracefully (fixes #8142) (#8143) (Teddy Katz)
4e52cfc Fix: Improve keyword-spacing typescript support (fixes #8110) (#8111) (Reyad Attiyat)
8f91e32 Fix: ignoreRestSiblings option didn’t cover arguments (fixes #8119) (#8120) (Toru Nagashima)

Documentation

a30eb8d Docs: improve documentation for RuleTester cases (#8162) (Teddy Katz)
9994889 Docs: Add missing space to create in no-use-before-define (#8166) (Justin Anastos)
4d542ba Docs: Remove unneeded statement about autofix (#8164) (alberto)
163d751 Docs: lines-around-comment doesn’t disallow empty lines (#8151) (alberto)
044bc10 Docs: Add details about “–fix” option for “sort-imports” rule (#8077) (Olivier Audard)

a6ce8f9 Build: Sort rules before dumping them to doc files (#8154) (Danny Andrews)
cbd7ded Build: display rules’ meta data in their docs (fixes #5774) (#8127) (Wilson Kurniawan)

Chores

0af9057 Chore: Upgrade to a patched version of mock-fs (fixes #8177) (#8188) (Teddy Katz)
a78ec9f Chore: upgrade coveralls to ^2.11.16 (#8161) (alberto)
7f1f4e5 Chore: remove unneeded devDeps linefix and gh-got (#8160) (alberto)
1c84922 Chore: upgrade eslint-plugin-node (#8156) (alberto)

ESLint v3.16.1 released

2017-02-22T00:00:00Z

Bug Fixes

ff8a80c Fix: duplicated autofix output for inverted fix ranges (fixes #8116) (#8117) (Teddy Katz)

Documentation

a421897 Docs: fix typo in arrow-parens.md (#8132) (Will Chen)
9fa2559 Docs: Add missing quotes in key-spacing rule (#8121) (Glenn Reyes)

f3a6ced Build: package.json update for eslint-config-eslint release (ESLint Jenkins)

Chores

22d7fbf Chore: fix invalid redeclared variables in tests (#8130) (Teddy Katz)
8d95598 Chore: fix output assertion typos in rule tests (#8129) (Teddy Katz)

ESLint v3.16.0 released

2017-02-20T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

Updated Token Iterator Methods

This release includes an exciting update for rule authors! Many of the token iterator methods provided by sourceCode have been updated with a new options parameter. Some highlights:

includeComments

Many of these methods can now include comments in the returned results using the { includeComments: true } option. The following methods are now deprecated:

sourceCode.getTokenOrCommentBefore(node)
sourceCode.getTokenOrCommentAfter(node)

Instead, please use the following, respectively:

sourceCode.getTokenBefore(node, { includeComments: true })
sourceCode.getTokenAfter(node, { includeComments: true })

filter

The filter option is a function that will filter the returned tokens. This allows for finding a specific token by type or value without having to create a loop.

For instance, the following:

let token = sourceCode.getTokenAfter(node);

while (token.type !== "Keyword") {
    token = sourceCode.getTokenAfter(token);
}

can now be written as:

const token = sourceCode.getTokenAfter(node, { filter: token => token.type === "Keyword" });

The update includes other options as well! For more details, please read the updated documentation.

Performance Improvements

Performance improvements were made to both the initial processing of source code as well as to autofixing.

Autofixing

Autofix support was added to one rule:

no-unused-labels

Enhancements

d89d0b4 Update: fix quotes false negative for string literals as template tags (#8107) (Teddy Katz)
360dbe4 Update: Improve error message when extend config missing (fixes #6115) (#8100) (alberto)
cfb65c5 Update: make no-lone-blocks report blocks in switch cases (fixes #8047) (#8062) (Teddy Katz)
290fb1f Update: Add includeComments to getTokenByRangeStart (fixes #8068) (#8069) (Kai Cataldo)
acc3301 Update: handle uncommon linebreaks consistently in rules (fixes #7949) (#8049) (Teddy Katz)
90fd555 Update: improve null detection in eqeqeq for ES6 regexes (fixes #8020) (#8042) (Teddy Katz)
834f45d Update: rewrite TokenStore (fixes #7810) (#7936) (Toru Nagashima)
1e3d4c6 Update: add fixer for no-unused-labels (#7841) (Teddy Katz)
f47fb98 Update: ensure semi-spacing checks import/export declarations (#8033) (Teddy Katz)
e228d56 Update: no-undefined handles properties/classes/modules (fixes #7964) (#7966) (Kevin Partington)

Bug Fixes

daf6f26 Fix: check output in RuleTester when errors is a number (fixes #7640) (#8097) (alberto)
7516303 Fix: sourceCode.getTokenAfter shouldn’t skip tokens after comments (#8055) (Toru Nagashima)
c53e034 Fix: unicode-bom fixer insert BOM in appropriate location (fixes #8083) (#8084) (pantosha)
16248e2 Fix: no-extra-boolean-cast incorrect Boolean() autofixing (fixes #7977) (#8037) (Jonathan Wilsson)

Documentation

14d146d Docs: Clarify --ext only works with directories (fixes #7939) (#8095) (alberto)
013a454 Docs: Add TSC meeting quorum requirement (#8086) (Kevin Partington)
6445d2a Docs: Add documentation for /* exported */ (fixes #7998) (#8065) (Lee Yi Min)
c596690 Docs: Clarify generator-star-spacing config example (fixes #8027) (#8034) (Hòa Trần)
a11d4a6 Docs: fix a typo in shareable configs documentation (#8036) (Dan Homola)

Dependency Upgrades

c7e64f3 Upgrade: mock-fs (#8070) (Toru Nagashima)

Chores

21be366 Chore: Ensuring eslint:recommended rules are sorted. (#8106) (Kevin Partington)
f62a724 Chore: use updated token iterator methods (#8103) (Kai Cataldo)
ff066dc Chore: Incorrect source code test text (#8096) (Jack Ford)
55ac302 Chore: fix the timing to define rules for tests (#8082) (Toru Nagashima)
591b74a Chore: enable operator-linebreak on ESLint codebase (#8064) (Teddy Katz)
fcc38db Chore: simplify and improve performance for autofix (#8035) (Toru Nagashima)
b04fde7 Chore: improve performance of SourceCode constructor (#8054) (Teddy Katz)
329dcdc Chore: unify checks for statement list parents (#8048) (Teddy Katz)
7bc92d9 Chore: fix invalid test cases (#8030) (Toru Nagashima)

ESLint v3.15.0 released

2017-02-03T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

New Rules

One new rule was added:

template-tag-spacing

Features

09546a4 New: template-tag-spacing rule (fixes #7631) (#7913) (Jonathan Wilsson)

Enhancements

c59a0ba Update: add ignoreRestSiblings option to no-unused-vars (#7968) (Zack Argyle)
fbd7c13 Update: ensure operator-assignment handles exponentiation operators (#7970) (Teddy Katz)
c5066ce Update: add “variables” option to no-use-before-define (fixes #7111) (#7948) (Teddy Katz)

Bug Fixes

f2a3580 Fix: no-extra-parens incorrect precedence (fixes #7978) (#7999) (alberto)
d6b6ba1 Fix: no-var should fix ForStatement.init (#7993) (Toru Nagashima)

Documentation

42390fd Docs: update README.md for team (#8016) (Toru Nagashima)
f2be7e3 Docs: Fix typo in object-curly-newline.md (#8002) (Danny Andrews)
df2351a Docs: Fix misleading section in brace-style documentation (#7996) (Teddy Katz)

Dependency Upgrades

99d386d Upgrade: Espree v3.4.0 (#8019) (Kai Cataldo)

Chores

d7ffd88 Chore: enable template-tag-spacing on ESLint codebase (#8005) (Teddy Katz)
5ae6e00 Chore: avoid unnecessary feature detection for Symbol (#7992) (Teddy Katz)
5d57c57 Chore: fix no-else-return lint error (refs #7986) (#7994) (Vitor Balocco)
62fb054 Chore: enable no-else-return on ESLint codebase (#7986) (Teddy Katz)
5cdfa99 Chore: enable no-unneeded-ternary on ESLint codebase (#7987) (Teddy Katz)

ESLint v3.14.1 released

2017-01-25T00:00:00Z

Bug Fixes

791f32b Fix: brace-style false positive for keyword method names (fixes #7974) (#7980) (Teddy Katz)
72d41f0 Fix: no-var autofix syntax error in single-line statements (fixes #7961) (#7962) (Teddy Katz)
b9e5b68 Fix: indent rule crash on sparse array with object (fixes #7959) (#7960) (Gyandeep Singh)

Documentation

d7a0add Docs: Add ESLint tutorial embed to getting started (#7971) (Jamis Charles)
8bcbf5d Docs: typo in prefer-promise-reject-errors (#7958) (Patrick McElhaney)

Chores

a7bd66a Chore: Adding assign/redeclare tests to no-undefined (refs #7964) (#7965) (Kevin Partington)

ESLint v3.14.0 released

2017-01-20T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

New Rules

Two new rules were added:

Autofixing

Autofix support was added to one rule:

no-else-return

Features

05e7432 New: no-multi-assign rule (fixes #6424) (#7904) (Stewart Rand)
f091d95 New: prefer-promise-reject-errors rule (fixes #7685) (#7689) (Teddy Katz)

Enhancements

243e47d Update: Add fixer for no-else-return (fixes #7863) (#7864) (Xander Dumaine)
a664e8a Update: add ignoreJSX option to no-extra-parens (Fixes #7444) (#7926) (Robert Rossmann)
bd5e219 Update: ensure brace-style validates class bodies (fixes #7608) (#7871) (Teddy Katz)
55f0cb6 Update: refactor brace-style and fix inconsistencies (fixes #7869) (#7870) (Teddy Katz)

Bug Fixes

506324a Fix: no-var does not fix if causes ReferenceError (fixes #7950) (#7953) (Toru Nagashima)
ca01e00 Fix: recognize all line terminators in func-call-spacing (fixes #7923) (#7924) (Francesco Trotta)
8ac3518 Fix: no-useless-computed-key false positive with __proto__ (#7934) (Teddy Katz)
7e04b33 Fix: Ignore inline plugin rule config in autoconfig (fixes #7860) (#7919) (Ian VanSchooten)
6448ba0 Fix: add parentheses in no-extra-boolean-cast autofixer (fixes #7912) (#7914) (Szymon Przybylski)
b3f2094 Fix: brace-style crash with lone block statements (fixes #7908) (#7909) (Teddy Katz)
427543a Fix: catastrophic backtracking in astUtils linebreak regex (fixes #7893) (#7898) (Teddy Katz)
995554c Fix: Correct typos in no-alert.md and lib/ast-utils.js (#7905) (Stewart Rand)

Documentation

c835e19 Docs: remove reference to deleted rule (#7942) (Alejandro Oviedo)
3c1e63b Docs: Improve examples for no-case-declarations (fixes #6716) (#7920) (Kevin Rangel)
5eb2e88 Docs: Correct typos in configuring.md (#7916) (Gabriel Delépine)

Chores

d6150e3 Chore: Enable comma-dangle on ESLint codebase (fixes #7725) (#7906) (Teddy Katz)
075ec25 Chore: update to use ES6 classes (refs #7849) (#7891) (Claire Dranginis)

ESLint v3.13.1 released

2017-01-09T00:00:00Z

Bug Fixes

3fc4e3f Fix: prefer-destructuring reporting compound assignments (fixes #7881) (#7882) (Teddy Katz)
f90462e Fix: no-extra-label autofix should not remove labels used elsewhere (#7885) (Teddy Katz)

ESLint v3.13.0 released

2017-01-06T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

New Rules

One new rule was added:

prefer-destructuring

Autofixing

Autofix support was added to the following rules:

Features

27424cb New: prefer-destructuring rule (fixes #6053) (#7741) (Alex LaFroscia)

Enhancements

cd4c025 Update: add fixer for no-extra-label (#7840) (Teddy Katz)
c9ba40a Update: add fixer for no-unneeded-ternary (#7540) (Teddy Katz)
dd56d87 Update: add object-shorthand option for arrow functions (fixes #7564) (#7746) (Teddy Katz)
d80d994 Update: add fixer for object-property-newline (fixes #7740) (#7808) (Teddy Katz)
1beecec Update: add fixer for operator-linebreak (#7702) (Teddy Katz)
ebcae1f Update: no-return-await with with complex return argument (fixes #7594) (#7595) (Dalton Santos)
7d1dc7e Update: Make default-case comment case-insensitive (fixes #7673) (#7742) (Robert Rossmann)

Bug Fixes

aa75c92 Fix: Ensure prefer-const fixes destructuring assignments (fixes #7852) (#7859) (Teddy Katz)
ca1f841 Fix: no-useless-return stack overflow on loops after throw (fixes #7855) (#7856) (Teddy Katz)
bf3ea3a Fix: capitalized-comments: Ignore consec. comments if first is invalid (#7835) (Kevin Partington)
0fc24f7 Fix: adapt new-paren rule so it handles TypeScript (fixes #7817) (#7820) (Philipp A)
df0b06b Fix: no-multiple-empty-lines perf issue on large files (fixes #7803) (#7843) (Teddy Katz)
2322733 Fix: Throw error if ruletester is missing required test scenarios (#7388) (Teddy Katz)
c5c3b21 Fix: no-implied-eval false positive on ‘setTimeoutFoo’ (fixes #7821) (#7836) (Teddy Katz)
fd4cd3b Fix: Disable no-var autofixer in some incorrect cases in loops (#7811) (Alan Pierce)
f20b9e9 Fix: Relax no-useless-escape’s handling of ‘]’ in regexes (fixes #7789) (#7793) (Teddy Katz)
3004c1e Fix: consistent-return shouldn’t report class constructors (fixes #7790) (#7797) (Teddy Katz)
428fbdf Fix: func-call-spacing “never” doesn’t fix w/ line breaks (fixes #7787) (#7788) (Kevin Partington)
6e61070 Fix: semi false positive before regex/template literals (fixes #7782) (#7783) (Teddy Katz)
ff0c050 Fix: remove internal property from config generation (fixes #7758) (#7761) (alberto)
8c3a962 Fix: syntax errors from object-shorthand autofix (fixes #7744) (#7745) (Teddy Katz)

Documentation

fbafdc0 Docs: padded-blocks never case (fixes #7868) (#7878) (alberto)
bf45893 Docs: Clarify that we only support Stage 4 proposals (#7845) (Kevin Partington)
7122205 Docs: Array destructuring example for no-unused-vars (fixes #7838) (#7839) (Remco Haszing)
1f25834 Docs: update outdated info in Architecture page (#7816) (Teddy Katz)
b938f1f Docs: Add an example for the spread operator to prefer-spread.md (#7802) (#7804) (butlermd)
b8ce2dc Docs: Remove .html extensions from links in developer-guide (#7805) (Kevin Partington)
aafebb2 Docs: Wrap placeholder sample in raw (#7798) (Daniel Lo Nigro)
bb648ce Docs: fix unclear example for no-useless-escape (#7781) (Teddy Katz)
8b296a2 Docs: fix in semi.md: correct instead of incorrect (#7779) (German Prostakov)

Dependency Upgrades

3493241 Upgrade: strip-json-comments ~v2.0.1 (Janus Troelsen)

Chores

4008022 Chore: Refactor to use ES6 Classes (Part 3)(refs #7849) (#7865) (Gyandeep Singh)
616611a Chore: Refactor to use ES6 Classes (Part 2)(refs #7849) (#7847) (Gyandeep Singh)
856084b Chore: Refactor to use ES6 Classes (Part 1)(refs #7849) (#7846) (Gyandeep Singh)
18fa521 Chore: use ast-utils helper functions in no-multiple-empty-lines (#7842) (Teddy Katz)
e21b36b Chore: add integration tests for cache files (refs #7748) (#7794) (Teddy Katz)
00dd96c Chore: enable array-bracket-spacing on ESLint codebase (#7830) (Teddy Katz)
bb6b73b Chore: replace unnecessary function callbacks with arrow functions (#7795) (Teddy Katz)
75b7ba4 Chore: enable object-curly-spacing on ESLint codebase (refs #7725) (#7770) (Teddy Katz)
f1bf5ec Chore: convert remaining old-style context.report() calls to the new API (#7763) (Teddy Katz)

ESLint v3.12.2 released

2016-12-14T00:00:00Z

Bug Fixes

dec3ec6 Fix: indent bug with AssignmentExpressions (fixes #7747) (#7750) (Teddy Katz)

Documentation

639b798 Docs: Use Object.prototype in examples (#7755) (Alex Reardon)

5344751 Build: Don’t create blogpost links from rule names within other words (#7754) (Teddy Katz)

ESLint v3.12.1 released

2016-12-12T00:00:00Z

Bug Fixes

0ad4d33 Fix: indent regression with function calls (fixes #7732, fixes #7733) (#7734) (Teddy Katz)

Documentation

ab246dd Docs: Rules restricting globals/properties/syntax are linked together (#7743) (Kevin Partington)
df2f115 Docs: Add eslint-config-mdcs to JSCS Migration Guide (#7737) (Joshua Koo)

4b77333 Build: avoid creating broken rule links in the changelog (#7731) (Teddy Katz)

ESLint v3.12.0 released

2016-12-09T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

Additional APIs

This version includes the addition of three new API methods:

getRules to linter
version to linter
version to CLIEngine

Apologies for the lack of clear documentation on the above - our API documentation needs an overhaul, and we plan on updating this in the near future.

New option for `eslint --init`

This version adds the ability to pick the airbnb-base config without eslint-plugin-react, for those who want to follow the Airbnb styleguide but do not use React.

New Rules

One new rule was added:

no-await-in-loop

Autofixing

Autofix support was added to the following rule:

capitalized-comments

Features

1d0d61d New: Add no-await-in-loop rule (#7563) (Nat Mote)
2cdfb4e New: Additional APIs (fixes #6256) (#7669) (Ilya Volodin)

Enhancements

e569225 Update: fix false positive/negative of yoda rule (fixes #7676) (#7695) (Toru Nagashima)
4278c42 Update: make no-obj-calls report errors for Reflect (fixes #7700) (#7710) (Tomas Echeverri Valencia)
b921d1f Update: add indent options for array and object literals (fixes #7473) (#7681) (Teddy Katz)
7079c89 Update: Add airbnb-base to init styleguides (fixes #6986) (#7699) (alberto)
f8786fb Update: add fixer for capitalized-comments (#7701) (Teddy Katz)

Bug Fixes

e95a230 Fix: indent “first” option false positive on nested arrays (fixes #7727) (#7728) (Teddy Katz)
81f9e7d Fix: Allow duplicated let declarations in prefer-const (fixes #7712) (#7717) (Teddy Katz)
abfd24f Fix: don’t validate schemas for disabled rules (fixes #7690) (#7692) (Teddy Katz)
0a2a7fd Fix: Allow \u2028 and \u2029 as string escapes in no-useless-escape (#7672) (Teddy Katz)

Documentation

4742d82 Docs: clarify the default behavior of operator-linebreak (fixes #7459) (#7726) (Teddy Katz)
63bb3f8 Docs: improve the documentation for the autofix API (#7716) (Teddy Katz)
90a5d29 Docs: Remove incorrect info about issue requirements from PR guide (#7691) (Teddy Katz)
f80c278 Docs: Add sails-hook-lint to integrations list (#7679) (Anthony M)
e96da3f Docs: link first instance of package.json (#7684) (Kent C. Dodds)
b30116c Docs: Fix code-blocks in spaced-comment docs (#7524) (Michał Gołębiowski)
76c33a9 Docs: Change Sails.js integration to active npm package (#7675) (Anthony M)

Dependency Upgrades

2ac07d8 Upgrade: Update globals dependency to 9.14.0 (#7683) (Aleksandr Oleynikov)

bf20e20 Build: include links to rule pages in release blogpost (#7671) (Teddy Katz)

Chores

a8489e2 Chore: Avoid parserOptions boilerplate in tests for ES6 rules (#7724) (Teddy Katz)

ESLint v3.11.1 released

2016-11-28T00:00:00Z

Bug Fixes

be739d0 Fix: capitalized-comments fatal error fixed (fixes #7663) (#7664) (Rich Trott)

Documentation

cc4cedc Docs: Fix a typo in array-bracket-spacing documentation (#7667) (Alex Guerrero)
f8adadc Docs: fix a typo in capitalized-comments documentation (#7666) (Teddy Katz)

ESLint v3.11.0 released

2016-11-25T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

New Rules

Two new rules were added:

More Autofixing

Autofix support was added to two rules:

Features

ad56694 New: capitalized-comments rule (fixes #6055) (#7415) (Kevin Partington)
89bd8de New: require-await rule (fixes #6820) (#7435) (Toru Nagashima)

Enhancements

7185567 Update: add fixer for operator-assignment (#7517) (Teddy Katz)
faf5f56 Update: fix false negative of quotes with \n in template (fixes #7646) (#7647) (Teddy Katz)
474e444 Update: add fixer for sort-imports (#7535) (Teddy Katz)

Bug Fixes

d50f6c1 Fix: incorrect location for no-useless-escape errors (fixes #7643) (#7645) (Teddy Katz)
5c9a4ad Fix: Prevent quotes from fixing templates to directives (fixes #7610) (#7617) (Teddy Katz)

Documentation

f9b70b3 Docs: Enable example highlighting in rules examples (ref #6444) (#7644) (Alex Guerrero)
54a993c Docs: Fix a typo in the require-yield.md (#7652) (Vse Mozhet Byt)
32a3547 Docs: Add absent quotes in rules documentation (#7625) (Denis Sikuler)
07124d1 Docs: add missing quote mark (+=" → “+=”) (#7613) (Sean Juarez)
8998043 Docs: fix wording in docs for no-extra-parens config (Michael Ficarra)

Dependency Upgrades

d90ca46 Upgrade: Update markdownlint dependency to 0.3.1 (fixes #7589) (#7592) (David Anson)

Chores

eadd808 Chore: Fix prefer-arrow-callback lint errors (#7651) (Kevin Partington)
b7432bd Chore: Ensure JS files are checked out with LF (#7624) (Kevin Partington)

ESLint v3.10.2 released

2016-11-15T00:00:00Z

Bug Fixes

0643bfe Fix: correctly handle commented code in indent autofixer (fixes #7604) (#7606) (Teddy Katz)
bd0514c Fix: syntax error after key-spacing autofix with comment (fixes #7603) (#7607) (Teddy Katz)
f56c1ef Fix: indent crash on parenthesized global return values (fixes #7573) (#7596) (Teddy Katz)

Documentation

100c6e1 Docs: Fix example for curly “multi-or-nest” option (#7597) (Will Chen)
6abb534 Docs: Update code of conduct link (#7599) (Nicholas C. Zakas)
8302cdb Docs: Update no-tabs to match existing standards & improve readbility (#7590) (Matt Stow)

ESLint v3.10.1 released

2016-11-14T00:00:00Z

Bug Fixes

8a0e92a Fix: handle try/catch correctly in no-return-await (fixes #7581) (#7582) (Teddy Katz)
c4dd015 Fix: no-useless-return stack overflow on unreachable loops (fixes #7583) (#7584) (Teddy Katz)

ESLint v3.10.0 released

2016-11-11T00:00:00Z

Highlights

This is a summary of some of the notable changes in this version of ESLint.

One new rule, no-return-await, was added.
no-extra-boolean-cast gained auto-fix functionality.
Certain cases caught by eqeqeq can now be auto-fixed.
New options were added to comma-style to check function parameters, function arguments, imports, and destructuring.
func-names gained a new option to recognize ES6 inferred names.

Features

66fe9ff New: no-return-await rule. (fixes #7537) (#7547) (Jordan Harband)

Enhancements

7ee039b Update: Add comma-style options for calls, fns, imports (fixes #7470) (Max Englander)
c3f4809 Update: Allow func-names to recognize inferred ES6 names (fixes #7235) (#7244) (Logan Smyth)
2bd1dd7 Update: avoid creating extra whitespace in arrow-body-style fixer (#7504) (Teddy Katz)
5003b1c Update: fix in/instanceof handling with space-infix-ops (fixes #7525) (#7552) (Teddy Katz)
1766524 Update: “Error type should be” assertion in rule-tester (fixes 6106) (#7550) (Frans Jaspers)
3c379ff Update: no-restricted-{imports,modules}: add “patterns” (fixes #6963) (#7433) (Jordan Harband)
af1fde1 Update: fix brace-style false negative on multiline node (fixes #7493) (#7496) (Teddy Katz)
3798aea Update: max-statements to report function name (refs #7260) (#7399) (Nicholas C. Zakas)
0c215fa Update: Add ArrowFunctionExpression support to require-jsdoc rule (#7518) (Gyandeep Singh)
8a3e717 Update: Fix lines-around-directive semicolon handling (fixes #7450) (#7483) (Teddy Katz)
e58cead Update: add a fixer for certain statically-verifiable eqeqeq cases (#7389) (Teddy Katz)
36338f0 Update: add fixer for no-extra-boolean-cast (#7387) (Teddy Katz)

Bug Fixes

b8d6e48 Fix: syntax errors created by object-shorthand autofix (fixes #7574) (#7575) (Teddy Katz)
0d60db7 Fix: Curly rule doesn’t account for leading comment (fixes #7538) (#7539) (Will Chen)
c0f4937 Fix: arrow-parens supports type annotations (fixes #7406) (#7436) (Toru Nagashima)
4613ba0 Fix: Add support for escape char in JSX. (#7461) (Scott Stern)
ea0970d Fix: curly false positive with no-semicolon style (#7509) (Teddy Katz)

Documentation

3e6131e Docs: explain config option merging (#7499) (Danny Andrews)
44eb274 Docs: Missing semicolon report was missing a comma (#7553) (James)
6dbda15 Docs: Document the optional defaults argument for RuleTester (#7548) (Teddy Katz)
e117b80 Docs: typo fix (#7546) (oprogramador)
a838b8e Docs: func-name-matching: update with “always”/“never” option (#7536) (Jordan Harband)
f5764ee Docs: Update example of results returned from executeOnFiles (#7362) (Simen Bekkhus)
a7f3976 Docs: Specify min ESLint version for new rule format (#7501) (cowchimp)
4f1fa67 Docs: Update copyright (#7497) (Nicholas C. Zakas)

578c373 Build: handle deprecated rules with no ‘replacedBy’ (refs #7471) (#7494) (Vitor Balocco)

Chores

670e060 Chore: make the object-shorthand tests more readable (#7580) (Teddy Katz)
1b3b65c Chore: ensure that files in tests/conf are linted (#7579) (Teddy Katz)
759525e Chore: Use process.exitCode instead of process.exit() in bin/eslint.js (#7569) (Teddy Katz)
25e5613 Chore: Remove incorrect test from indent.js. (#7531) (Scott Stern)
0dea0ac Chore: Add Node 7 to travis ci build (#7506) (Gyandeep Singh)
183def6 Chore: enable prefer-arrow-callback on ESLint codebase (fixes #6407) (#7503) (Teddy Katz)

ESLint v3.9.1 released

2016-10-31T00:00:00Z

Bug Fixes

2012258 Fix: incorrect indent check for array property access (fixes #7484) (#7485) (Teddy Katz)
8a71d4a Fix: no-useless-return false positive on conditionals (fixes #7477) (#7482) (Teddy Katz)
56a662b Fix: allow escaped backreferences in no-useless-escape (fixes #7472) (#7474) (Teddy Katz)

Documentation

8ba68a3 Docs: Update broken link (#7490) (Devinsuit)
65231d8 Docs: add the “fixable” icon for no-useless-return (#7480) (Teddy Katz)

fffdf13 Build: Fix prefer-reflect rule to not crash site gen build (#7471) (Ilya Volodin)

ESLint v3.9.0 released

2016-10-28T00:00:00Z

Highlights

This release includes some exciting new features, including a new results formatter and the ability for ESLint to support enhanced parsers!

New formatter

As part of our continuing effort to support our users coming from JSCS, we’re excited to release the new codeframe formatter!

error: Missing semicolon (semi) at file.js:1:13:
> 1 | var a = true
    |             ^
  2 |
  3 |


warning: There should be no space after '{' (object-curly-spacing) at file2.js:1:9:
> 1 | var b = { c: true};
    |         ^
  2 |
  3 |


1 error and 1 warning found.

Enhanced parsers

ESLint now supports enhanced parsers, which allows parsers to provide ESLint-specific services and functionality. This allows ESLint to support added functionality such as parsing type checkers.

New Rules

no-useless-return

New Rule Options

func-name-matching: nameMatches
indent: CallExpression
max-len: ignoreRegExpLiterals

New autofixing

Deprecated rules

With this release we deprecated prefer-reflect rule. The original intent of this rule now seems misguided as we have come to understand that Reflect methods are not actually intended to replace the Object counterparts the rule suggests, but rather exist as low-level primitives to be used with proxies in order to replicate the default behavior of various previously existing functionality. This rule will not be replaced.

Features

e46666b New: Codeframe formatter (fixes #5860) (#7437) (Vitor Balocco)
d933516 New: no-useless-return rule (fixes #7309) (#7441) (Toru Nagashima)
cbbe420 New: Support enhanced parsers (fixes #6974) (#6975) (Nicholas C. Zakas)

Enhancements

644d25b Update: Add an ignoreRegExpLiterals option to max-len (fixes #3229) (#7346) (Wilfred Hughes)
5e7af30 Update: Add CallExpression option for indent (fixes #5946) (#7189) (Teddy Katz)
e064a25 Update: add fixer for arrow-body-style (#7240) (Teddy Katz)
e0fe727 Update: add fixer for brace-style (fixes #7074) (#7347) (Teddy Katz)
ee3bcea Update: add fixer for newline-after-var (fixes #5959) (#7375) (Teddy Katz)
5ed8b9b Update: Deprecate prefer-reflect (fixes #7226) (#7464) (Kai Cataldo)
3813988 Update: fix false negative of no-extra-parens (fixes #7122) (#7432) (Toru Nagashima)
c675d7d Update: Fix no-useless-escape false negative in regexes (fixes #7424) (#7425) (Teddy Katz)
1d5146f Update: fix wrong indentation about catch,finally (#7371) (Toru Nagashima)
d257428 Update: func-name-matching: add “always”/“never” option (fixes #7391) (#7428) (Jordan Harband)

Bug Fixes

8dfd802 Fix: avoid camelcase false positive with NewExpressions (fixes #7363) (#7409) (Teddy Katz)
6e9ff08 Fix: indent.js to support multiline array statements. (#7237) (Scott Stern)
16367a8 Fix: Return statement spacing. Fix for indent rule. (fixes #7164) (#7197) (Imad Elyafi)
c710584 Fix: support for MemberExpression with function body. (#7400) (Scott Stern)
b200086 Fix: Support type annotations in array-bracket-spacing (#7445) (Jimmy Jia)

Documentation

85d7e24 Docs: add additional examples for MemberExpressions in Indent rule. (#7408) (Scott Stern)
e8159b4 Docs: Fix typo and explain static func calls for class-methods-use-this (#7421) (Scott O’Hara)
23062e2 Docs: Fix typo in no-unexpected-multiline (fixes #7442) (#7447) (Denis Sikuler)
2aa1107 Docs: Include note on fatal: true in the node.js api section (#7376) (Simen Bekkhus)
6875576 Docs: Remove broken links to jslinterrors.com (fixes #7368) (#7369) (Dannii Willis)

Build

f8153ad Build: Ensure absolute links in docs retain .md extensions (fixes #7419) (#7438) (Teddy Katz)
2c8ed2d Build: ensure that all files are linted on bash (fixes #7426) (#7427) (Teddy Katz)

Chores

18ff70f Chore: Enable no-useless-escape (#7403) (Vitor Balocco)
77e3a34 Chore: Pin mock-fs dev dependency (#7466) (Gyandeep Singh)
92ad43b Chore: Update deprecated rules in conf/eslint.json (#7467) (Kai Cataldo)

Upgrades

fe0d903 Upgrade: Shelljs to ^0.7.5 (fixes #7316) (#7465) (Gyandeep Singh)

ESLint v3.8.1 released

2016-10-17T00:00:00Z

Bug Fixes

681c78a Fix: comma-dangle was confused by type annotations (fixes #7370) (#7372) (Toru Nagashima)
7525042 Fix: Allow useless escapes in tagged template literals (fixes #7383) (#7384) (Teddy Katz)

Documentation

9106964 Docs: Fix broken link for stylish formatter (#7386) (Vitor Balocco)
49d3c1b Docs: Document the deprecated meta property (#7367) (Randy Coulman)
19d2996 Docs: Relax permission for merging PRs (refs eslint/tsc-meetings#20) (#7360) (Brandon Mills)

ESLint v3.8.0 released

2016-10-14T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Additional Property on Linting Results

If you’re using the ESLint Node.js API or writing a custom formatter, you’ll find that result object for each file now has a source property. This property contains the original source code from the file, allowing formatters to output contextual information along with linting error messages. This new source property on the file results object is intended to replace the source property on the lint message object, which will be removed in a later release. If you have a custom formatter making use of the source property on the lint message object, we recommend updating your formatter to check for the existence of the source property on the file results object and to use it if found. See the documentation for more information.

New Rules

func-name-matching

New Options

comma-dangle … arrays, objects, imports, exports, and functions.
space-before-function-paren … asyncArrow
wrap-iife … functionPrototypeMethods

New autofixing

Features

cd72bba New: func-name-matching rule (fixes #6065) (#7063) (Annie Zhang)

Enhancements

c8796e9 Update: comma-dangle supports trailing function commas (refs #7101) (#7181) (Toru Nagashima)
c4abaf0 Update: space-before-function-paren supports async/await (refs #7101) (#7180) (Toru Nagashima)
5266793 Update: no-useless-escape checks template literals (fixes #7331) (#7332) (Kai Cataldo)
b08fb91 Update: add source property to LintResult object (fixes #7098) (#7304) (Vitor Balocco)
c1470b5 Update: Make the prefer-template fixer unescape quotes (fixes #7330) (#7334) (Teddy Katz)
f8387c1 Update: add fixer for prefer-spread (#7283) (Teddy Katz)
52dfce5 Update: add fixer for one-var-declaration-per-line (#7295) (Teddy Katz)
0e994ae Update: Improve the error messages for no-unused-vars (fixes #7282) (#7315) (Teddy Katz)
72f394d Update: Fix false negative of no-multiple-empty-lines (fixes #7312) (#7313) (Teddy Katz)
756bc5a Update: Use characters instead of code units for max-len (#7299) (Teddy Katz)
a12d1a9 Update: add fixer for no-lonely-if (#7202) (Teddy Katz)
2ffe516 Update: add fixer for curly (#7105) (Teddy Katz)
ac3504d Update: add functionPrototypeMethods to wrap-iife (fixes #7212) (#7284) (Eli White)
5e16fb4 Update: add fixer for no-extra-bind (#7236) (Teddy Katz)

Bug Fixes

d0d3b28 Fix: id-length rule incorrectly firing on member access (fixes #6475) (#7365) (Burak Yiğit Kaya)
2729d94 Fix: Don’t report setter params in class bodies as unused (fixes #7351) (#7352) (Teddy Katz)
5d08c33 Fix: Handle parentheses correctly in yoda fixer (fixes #7326) (#7327) (Teddy Katz)
55b5146 Fix: RuleTester didn’t support mocha --watch (#7287) (Toru Nagashima)
52da71e Fix: Don’t require commas after rest properties (fixes #7297) (#7298) (Teddy Katz)
c9a7ec5 Fix: Improving optionator configuration for --print-config (#7206) (Kevin Partington)
51bfade Fix: avoid object-shorthand crash with spread properties (fixes #7305) (#7306) (Teddy Katz)
1418384 Fix: Don’t require semicolons before ++/-- (#7252) (Adrian Heine né Lang)

Documentation

d840afe Docs: remove broken link from no-loop-func doc (#7342) (Michael McDermott)
16d495d Docs: Updating CLI overview with latest changes (#7335) (Kevin Partington)

Chores

ee60acf Chore: add integration tests for autofixing (fixes #5909) (#7349) (Teddy Katz)
0b85004 Chore: Enable prefer-template (fixes #6407) (#7357) (Kai Cataldo)
ca1947b Chore: Update pull request template (refs eslint/tsc-meetings#20) (#7359) (Brandon Mills)
0db4164 Chore: run prefer-template autofixer on test files (refs #6407) (#7354) (Kai Cataldo)
3b11d3f Chore: refactor no-multiple-empty-lines (#7314) (Teddy Katz)
93214aa Chore: Convert non-lib/test files to template literals (refs #6407) (#7329) (Kai Cataldo)

ESLint v3.7.1 released

2016-10-03T00:00:00Z

Bug Fixes

3dcae13 Fix: Use the correct location for comma-dangle errors (fixes #7291) (#7292) (Teddy Katz)
cb7ba6d Fix: no-implicit-coercion should not fix ~. (fixes #7272) (#7289) (Eli White)

Documentation

8ec82ee Docs: change links of templates to raw data (#7288) (Toru Nagashima)

Chores

ce590e2 Chore: Add additional tests for bin/eslint.js (#7290) (Teddy Katz)

ESLint v3.7.0 released

2016-09-30T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint. Though it’s a smaller release, it does include the ability to autofix a number of rules!

Autofixing

In addition to linting code, many of the rules can automatically fix errors using the --fix flag. This can be a huge time saver for developers using ESLint on a pre-existing codebase! The following rules can now be autofixed:

Enhancements

c05a19c Update: add fixer for prefer-numeric-literals (#7205) (Teddy Katz)
2f171f3 Update: add fixer for no-undef-init (#7210) (Teddy Katz)
332d213 Update: Ensure indent handles nested functions correctly (fixes #7249) (#7265) (Teddy Katz)
c36d842 Update: add fixer for no-useless-computed-key (#7207) (Teddy Katz)
18376cf Update: add fixer for lines-around-directive (#7217) (Teddy Katz)
f8e8fab Update: add fixer for wrap-iife (#7196) (Teddy Katz)
cd1dc57 Update: Add a fixer for dot-location (#7186) (Teddy Katz)
89787b2 Update: for yoda, add a fixer (#7199) (Teddy Katz)
e3f95de Update: Fix no-extra-parens false negative (fixes #7229) (#7231) (Teddy Katz)

Bug Fixes

2fee8ad Fix: object-shorthand’s consistent-as-needed option (issue #7214) (#7215) (Naomi Jacobs)
dffb4fa Fix: no-unused-vars false positive (fixes #7250) (#7258) (Toru Nagashima)
742ae67 Fix: avoid indent and no-mixed-spaces-and-tabs conflicts (fixes #7248) (#7266) (Teddy Katz)
85b8714 Fix: Use error templates even when reading from stdin (fixes #7213) (#7223) (Teddy Katz)

Documentation

876d747 Docs: Steps for adding new committers/TSCers (#7221) (Nicholas C. Zakas)
4448cec Docs: Adding missing ES8 reference to configuring (#7271) (Kevin Partington)
558b444 Docs: Add @not-an-aardvark to development team (#7279) (Ilya Volodin)
66adac1 Docs: correction in prefer-reflect docs (fixes #7069) (#7150) (Scott Stern)
2909c19 Docs: Fix typo in object-shorthand docs (#7267) (Brian Donovan)
722c68c Docs: add code fences to the issue template (#7254) (Teddy Katz)

Chores

7bb800d Chore: add internal rule to enforce meta.docs conventions (fixes #6954) (#7155) (Vitor Balocco)

ESLint v3.6.1 released

2016-09-26T00:00:00Z

Documentation

87625fa Docs: Improve eol-last examples in docs (#7227) (Chainarong Tangsurakit)
de8eaa4 Docs: class-methods-use-this: fix option name (#7224) (Jordan Harband)
2355f8d Docs: Add Brunch plugin to integrations (#7225) (Aleksey Shvayka)
a5817ae Docs: Default option from operator-linebreak is afterand not always (#7228) (Konstantin Pschera)

Dependency Upgrades

b467436 Upgrade: Upgrade Espree to 3.3.1 (#7253) (Ilya Volodin)

299a563 Build: Do not strip .md extension from absolute URLs (#7222) (Kai Cataldo)

Chores

27042d2 Chore: removed unused code related to scopeMap (#7218) (Yang Su)
d154204 Chore: Lint bin/eslint.js (#7243) (Kevin Partington)

ESLint v3.6.0 released

2016-09-23T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Support for ES2017

With this release, we support ES2017 syntax natively. To activate ES2017 parser option, you need to update parser option (in your .eslintrc.* file).

{
    "parserOptions": {
        "ecmaVersion": 2017,
        "sourceType": "module"
    }
}

Rules enhanced to support ES2017

Auto-Fix

Four rules gained support for the --fix command line option:

Enhancements

1b05d9c Update: add fixer for strict (fixes #6668) (#7198) (Teddy Katz)
aaa3779 Update: Allow space-unary-ops to handle await expressions (#7174) (Teddy Katz)
91bf477 Update: add fixer for prefer-template (fixes #6978) (#7165) (Teddy Katz)
745343f Update: no-extra-parens supports async/await (refs #7101) (#7178) (Toru Nagashima)
462a3f7 Update: keyword-spacing supports async/await (refs #7101) (#7179) (Toru Nagashima)
709a734 Update: Allow template string in valid-typeof comparison (fixes #7166) (#7168) (Teddy Katz)
16bb802 Update: Ensure arrow-parens handles async arrow functions correctly (#7176) (Teddy Katz)
c118d21 Update: Let no-restricted-properties check destructuring (fixes #7147) (#7151) (Teddy Katz)
95c777a Update: Make no-restricted-properties more flexible (fixes #7137) (#7139) (Teddy Katz)
0fdf23c Update: fix quotes rule’s false negative (fixes #7084) (#7141) (Toru Nagashima)
f2a789d Update: fix no-unused-vars false negative (fixes #7124) (#7143) (Toru Nagashima)
e016384 Update: add fixer for quote-props (fixes #6996) (#7095) (Teddy Katz)
8b3fc32 Update: Make indent report lines with mixed spaces/tabs (fixes #4274) (#7076) (Teddy Katz)
b39ac2c Update: add fixer for no-regex-spaces (#7113) (Teddy Katz)
a876673 Update: no-implicit-coercion checks TemplateLiterals (fixes #7062) (#7121) (Kai Cataldo)
22edd8a Update: class-methods-use-this: exceptions option (fixes #7085) (#7120) (Jordan Harband)
bcfa3e5 Update: Add always/never option to eol-last (fixes #6938) (#6952) (kdex)

Bug Fixes

8e1fee1 Fix: Handle number literals correctly in no-whitespace-before-property (#7185) (Teddy Katz)
f71937a Fix: Don’t report async/generator callbacks in array-callback-return (#7172) (Teddy Katz)
461b015 Fix: Handle async functions correctly in prefer-arrow-callback fixer (#7173) (Teddy Katz)
7ea3e4b Fix: Handle await expressions correctly in no-unused-expressions (#7175) (Teddy Katz)
9e0b068 Fix: valid-jsdoc does not throw on FieldType without value (fixes #7184) (#7187) (Kai Cataldo)
6148d85 Fix: Report columns for eol-last correctly (fixes #7136) (#7149) (kdex)
28ddcf8 Fix: max-len: ignoreTemplateLiterals: handle 3+ lines (fixes #7125) (#7138) (Jordan Harband)
76acbb5 Fix: include LogicalExpression in indent length calc (fixes #6731) (#7087) (Alec)
afd132a Fix: line-comment-position “above” string option now works (fixes #7100) (#7102) (Kevin Partington)
c85fd84 Fix: max-statements-per-line rule to force minimum to be 1 (fixes #7051) (#7092) (Scott Stern)
6ae660b Fix: Don’t report comparisons of two typeof expressions (fixes #7078) (#7082) (Teddy Katz)

Documentation

0a36138 Docs: Update ecmaVersion instructions (#7195) (Nicholas C. Zakas)
4b5d9b7 Docs: Update process for evaluating proposals (fixes #7156) (#7183) (Kai Cataldo)
660e091 Docs: Update rule descriptions (fixes #5912) (#7152) (Kenneth Williams)
cc80467 Docs: Update PR templates for formatting (#7128) (Nicholas C. Zakas)
7e8316f Docs: Update release process (#7127) (Nicholas C. Zakas)
ac0bb62 Docs: Fixes examples for allowTemplateLiterals (fixes #7115) (#7135) (Zoe Ingram)
0ca26d9 Docs: Distinguish examples for space-before-blocks (#7132) (Timo Tijhof)
e462e47 Docs: updates category of no-restricted-properties (fixes #7112) (#7118) (Alec)
710f205 Docs: Fix typos in Issues section of Maintainer’s Guide (#7114) (Kai Cataldo)
546a3ca Docs: Clarify that linter does not process configuration (fixes #7108) (#7110) (Kevin Partington)
0d50943 Docs: Elaborate on guard-for-in best practice (fixes #7071) (#7094) (Dallon Feldner)
58e6d76 Docs: Fix examples for no-restricted-properties (#7099) (not-an-aardvark)
6cfe519 Docs: Corrected typo in line-comment-position rule doc (#7097) (Alex Mercier)
f02e52a Docs: Add fixable note to no-implicit-coercion docs (#7096) (Brandon Mills)

Dependency Upgrades

35f7be9 Upgrade: espree to 3.2.0, remove tests with SyntaxErrors (fixes #7169) (#7170) (Teddy Katz)

Chores

2d10657 Chore: add tests for generator-star-spacing and async (refs #7101) (#7182) (Toru Nagashima)
8db4f0c Chore: Enable typeof check for no-undef rule in eslint-config-eslint (#7103) (Teddy Katz)
1738b2e Chore: fix name of internal-no-invalid-meta test file (#7142) (Vitor Balocco)
9a2aefb Chore: Don’t require an issue reference in check-commit npm script (#7104) (Teddy Katz)

Changes to Issue and Pull Request Policies

2016-09-15T00:00:00Z

From the beginning of the project, ESLint has always required issues for every pull request containing code. There were a number of reasons for that, mostly related to how we were triaging and handling incoming requests as well as the limitations the GitHub issue tracker imposed on us. Since that time, there have been a lot of improvements to the GitHub issue and pull request trackers, and as such, we’ve been able to make some changes.

Most Pull Requests No Longer Require Issues

We’ve lifted the restriction that all pull requests require issues. For almost all types of changes, you can now submit pull requests directly without an issue. We’ve added a pull request template, and as long as you fill out the required information in that template, you can feel free to submit pull requests without opening issues first.

There are, however, two types of changes that still require issues:

Any breaking change.
Any changes to the core.

Breaking and core changes have a high potential to affect end-users, and so we still want to understand that impact before people spend time writing code.

End-of-Life Periods for Issues

One of the things we’ve heard from contributors is that it’s frustrating when an issue gets stuck without resolution. We’ve tried, from the start, to give feedback as quickly as possible to issues and pull requests. However, as ESLint has grown, the number of issues and pull requests has grown quite large and has made it hard for the team to handle.

Different teams in the open source community handle this problem differently. Some teams choose to never close issues and just leave all of them open indefinitely in case someone wants to fix them. Some teams use bots to automatically close issues that are older than a set amount of time. The ESLint team wasn’t too happy with these choices, so we arrived on a more manual process that is a mixture of the two.

Our top goal is to give feedback quickly, and since most issues are requests for the ESLint team to make a change, we want to let you know whether or not we’ll be making that change. The best way to do that is to close the issue with an appropriate comment. The rules we’ve established are:

An issue that hasn’t been accepted may be closed after 21 days. (Only accepted issues end up on the roadmap.)
An accepted issue may be closed after 90 days if no one has agreed to implement it.

While we wish we could commit to implementing every good idea for ESLint, the reality is that many requests will not end up on the formal roadmap. The ESLint team is a team of volunteers working in their spare time, and as such, the amount of time available for work is small. We feel that closing issues and giving a clear indication that the requested change will not be made is a more honest approach than leaving issues open forever just in case someone decides they’d like to contribute a change. In our experience, issues that are open for 90 days or more are rarely ever addressed and just serve to confuse everyone about their status.

Note: If you’re passionate about a change, consider submitting a pull request instead of an issue. A lot of times, we just don’t have the extra bandwidth to accommodate significant requests, but we can guide others through the changes. Submitting a pull request increases the chances that your change will land (though it does not guarantee it).

Continuing to Learn

As always, we’ll continue to evaluate our issue and pull request policies based on feedback from the ESLint team and the community as a whole. We hope these new changes will help the ESLint community continue to grow by streamlining the process for accepting contributions.

ESLint v3.5.0 released

2016-09-09T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

New Rules

The following new rules were added in this release:

Auto-Fix

Eight rules gained support for the --fix command line option:

Features

6d97c18 New: max-len: ignoreStrings+ignoreTemplateLiterals (fixes #5805) (#7049) (Jordan Harband)
3960617 New: prefer-numeric-literals rule (fixes #6068) (#7029) (Annie Zhang)
46cb690 New: no-restricted-properties rule (fixes #3218) (#7017) (Eli White)
8277357 New: line-comment-position rule (fixes #6077) (#6953) (alberto)
c1f0d76 New: lines-around-directive rule (fixes #6069) (#6998) (Kai Cataldo)

Enhancements

08fa538 Update: fix false negative of arrow-spacing (fixes #7079) (#7080) (Toru Nagashima)
cec65e3 Update: add fixer for no-floating-decimal (fixes #7070) (#7081) (not-an-aardvark)
538d258 Update: make no-implicit-coercion support autofixing. (fixes #7056) (#7061) (Eli White)
883316d Update: add fixer for prefer-arrow-callback (fixes #7002) (#7004) (not-an-aardvark)
7502eed Update: auto-fix for comma-style (fixes #6941) (#6957) (Gyandeep Singh)
645dda5 Update: add fixer for dot-notation (fixes #7014) (#7054) (not-an-aardvark)
656bb6e Update: add fixer for newline-before-return (fixes #5958) (#7050) (Vitor Balocco)
e118728 Update: add fixer for wrap-regex (fixes #7013) (#7048) (not-an-aardvark)
f4fcd1e Update: add more indent options for functions (fixes #6052) (#7043) (not-an-aardvark)
657eee5 Update: add fixer for new-parens (fixes #6994) (#7047) (not-an-aardvark)
ff19aa9 Update: improve max-statements-per-line message (fixes #6287) (#7044) (Jordan Harband)
22c7e09 Update: no-magic-numbers false negative on reassigned vars (fixes #4616) (#7028) (not-an-aardvark)
be29599 Update: Throw error if whitespace found in plugin name (fixes #6854) (#6960) (Jesse Ostrander)
00b3042 Update: Pass file path to parse function (fixes #5344) (#7024) (Annie Zhang)
8e77f16 Update: new-parens false negative (fixes #6997) (#6999) (Toru Nagashima)

Bug Fixes

2a3f699 Fix: Column number for no-multiple-empty-lines (fixes #7086) (#7088) (Ian VanSchooten)
d9513b7 Fix: Allow linting of .hidden files/folders (fixes #4828) (#6844) (Ian VanSchooten)
2657846 Fix: no-console ignores user-defined console (fixes #7010) (#7058) (Toru Nagashima)
1f995c3 Fix: no-implicit-coercion string concat false positive (fixes #7057) (#7060) (Kai Cataldo)
4063a79 Fix: Rule message placeholders can be inside braces (fixes #6988) (#7041) (Kevin Partington)
256c4a2 Fix: Allow separate mode option for multiline and align (fixes #6691) (#6991) (Annie Zhang)

Documentation

6947299 Docs: Add info about closing accepted issues to docs (fixes #6979) (#7089) (Kai Cataldo)
d30157a Docs: Add link to awesome-eslint in integrations page (#7090) (Vitor Balocco)
457be1b Docs: Update so issues are not required (fixes #7015) (#7072) (Nicholas C. Zakas)
6718749 Docs: Clarify that es6 env also sets ecmaVersion to 6 (#7067) (Jérémie Astori)
52e8d9c Docs: Clean up sort-vars (#7045) (Matthew Dunsdon)
3f13325 Docs: Add kaicataldo and JamesHenry to our teams (#7039) (alberto)
326f457 Docs: Add missing ‘to’ in no-restricted-modules (#7022) (Oskar Risberg)
61f1de0 Docs: Fix typo in no-debugger (#7019) (Denis Ciccale)
a989a7c Docs: Declaring dependency on eslint in shared config (fixes #6617) (#6985) (alberto)
6869c60 Docs: Fix minor typo in no-extra-parens doc (#6992) (Jérémie Astori)
28f1619 Docs: Update the example of SwitchCase (#6981) (fish)

Chores

fa760f9 Chore: no-regex-spaces uses internal rule message format (fixes #7052) (#7053) (Kevin Partington)
4126f12 Chore: Rule messages use internal rule message format (fixes #6977) (#6989) (Kevin Partington)

ESLint v3.4.0 released

2016-08-26T00:00:00Z

Highlights

This is a summary of the major changes you need to know about for this version of ESLint.

Fix For Configuring Scoped Plugin Rules

We discovered a significant bug (#6362) when using scoped plugins. Scoped plugins use npm scopes such as @foo/eslint-plugin-bar. Due to a bug in ESLint, if you had a rule baz in the plugin @foo/eslint-plugin-bar, you would have to configure it without the scope, such as:

rules:
  bar/baz: error

This is problematic because it’s possible that an unscoped plugin eslint-plugin-bar might exist and need to be configured in the same way.

Important: Starting in this release, you should now configure scoped plugin rules using the scope as a prefix. The previous example should now be written as:

rules:
  @foo/bar/baz: error

The other format will continue work until we release ESLint v4.0.0, at which point only the format using the package scope will work. We encourage you to update your configuration files as quickly as possible so as not to be caught up in the change for version 4.0.0.

Performance Improvements

We’ve been steadily improving the performance of traversing directories in ESLint. Previously, we made a change that dramatically improved the speed of directory traversal for those who weren’t using .eslintignore (#5679). In this release, we’ve continued on to improve the speed for those using .eslintignore as well (#6710).

New Ways to Configure ECMAScript Version

ESLint has supported the ecmaVersion property for specifying which versions of ECMAScript syntax to enable. Prior to this release, you could use 3, 5, 6, and 7. However, the official ECMAScript standard is now being defined by year, so some new users found this confusing. As such, we’ve added the ability to use 2015 and 2016 in the ecmaVersion field (these correspond to 6 and 7, respectively), so that going forward we can use the more appropriate year-based values.

New Rules

The following new rules were added in this release:

Features

21ab784 New: do not remove non visited files from cache. (fixes #6780) (#6921) (Roy Riojas)
0d268f1 New: symbol-description rule (fixes #6778) (#6825) (Jarek Rencz)
a5189a6 New: class-methods-use-this rule (fixes #5139) (#6881) (Gyandeep Singh)

Enhancements

c210510 Update: add fixer for no-extra-parens (fixes #6944) (#6950) (not-an-aardvark)
d6fd064 Update: Add never option to multiline-ternary (fixes #6751) (#6905) (Kai Cataldo)
cf2242c Update: requireStringLiterals option for valid-typeof (fixes #6698) (#6923) (not-an-aardvark)
1563808 Update: add support for ecmaVersion 20xx (fixes #6750) (#6907) (Kai Cataldo)

Bug Fixes

ca3d448 Fix: prefer-const false negative about eslintUsed (fixes #5837) (#6971) (Toru Nagashima)
3e522be Fix: false negative of indent with else if statements (fixes #6956) (#6965) (not-an-aardvark)
3c710c9 Fix: rename “AirBnB” => “Airbnb” init choice (fixes #6969) (Harrison Shoff)
7660b39 Fix: object-curly-spacing for type annotations (fixes #6940) (#6945) (Toru Nagashima)
3a1763c Fix: enable @scope/plugin/ruleId-style specifier (refs #6362) (#6939) (Toru Nagashima)
a063d4e Fix: no-cond-assign within a function expression (fixes #6908) (#6909) (Patrick McElhaney)
8851ddd Fix: Improve pref of globbing by inheriting glob.GlobSync (fixes #6710) (#6783) (Kael Zhang)
8561389 Fix: no-trailing-spaces wrong fixing (fixes #6933) (#6937) (Toru Nagashima)

Documentation

1153955 Docs: Draft of JSCS migration guide (refs #5859) (#6942) (Nicholas C. Zakas)
2dfb290 Docs: Distinguish examples in rules under Stylistic Issues part 7 (#6760) (Kenneth Williams)
6a92be5 Docs: Update semantic versioning policy (#6935) (alberto)
d8b770c Docs: Change rule descriptions for consistent casing (#6915) (Brandon Mills)

16db93a Build: Tag docs, publish release notes (fixes #6892) (#6934) (Nicholas C. Zakas)

Chores

0cf1d55 Chore: Fix object-shorthand errors (fixes #6958) (#6959) (Kai Cataldo)
c676322 Chore: Use object-shorthand batch 3 (refs #6407) (#6914) (Kai Cataldo)

ESLint Blog

ESLint v9.18.0 released

Highlights

Stable TypeScript configuration file support

no-shadow-restricted-names checks imports and class names

Allowed method names in no-config problems

Features

Bug Fixes

Documentation

Chores

ESLint v9.17.0 released

Highlights

no-unused-vars Suggestions

Nullish message.fix Allowed

Features

Bug Fixes

Documentation

Chores

ESLint v9.16.0 released

Highlights

ignoreComputedKeys option for sort-keys

Language-agnostic no-restricted-syntax

Features

Documentation

Chores

ESLint v9.15.0 released

Highlights

meta.defaultOptions

Other notable changes

Features

Bug Fixes

Documentation

Chores

ESLint v9.14.0 released

Highlights

Support for Import Attributes

Support for RegExp Modifiers

Improved configuration file lookup performance

Features

Bug Fixes

Documentation

Build Related

Chores

ESLint v9.13.0 released

Highlights

Features

Bug Fixes

Documentation

Chores

no-unused-binary-expressions: From code review nit to ecosystem improvements

Timeline

Reflections

What’s Next

Conclusion

ESLint v9.12.0 released

Highlights

Experimental configuration file resolution

Other notable changes

Features

Bug Fixes

Documentation

Chores

ESLint now officially supports linting of JSON and Markdown

JSON linting with @eslint/json

Markdown linting with @eslint/markdown

Creating custom rules and using Code Explorer

Write your own language plugin

Conclusion

ESLint v9.11.1 released

Highlights

Bug Fixes

Documentation

Chores

ESLint v9.11.0 released

Highlights

Features

Bug Fixes

Documentation

Build Related

Chores

`no-shadow-restricted-names` checks imports and class names

Allowed method names in `no-config` problems

`no-unused-vars` Suggestions

Nullish `message.fix` Allowed

`ignoreComputedKeys` option for `sort-keys`

Language-agnostic `no-restricted-syntax`

`meta.defaultOptions`

JSON linting with `@eslint/json`

Markdown linting with `@eslint/markdown`