facebook/react

* added "Handling Multiple Inputs"

* renamed and added a codepen

* simplified the example

Tweaked captured error log slightly based on feedback. Normalized stack format/display for different browsers

…8815)

* Updating Thinking in React doc to replace refs

* Updating doc copy to reflect changes to example

* use an easier word

The word `mandatory` is relatively difficult for people with ESL (English as a second language), so I propose an alternative word.
This would be much easier to understand.

* use simpler word

* Added flow to PR template

* Added record-tests step to PR template and contribution docs

* Updated order of PR checks

* add docs for building with Rollup

* Tiny unrelated fix

* FiberDebugger uses packages built in local

* Fix key warnings in FiberDebugger

* Remove react packages from package.json and yarn.lock for using pacakges built in local

* Remove fiber.js from `files` in package.json

…8667)

Add unit test to onlyChild to ensure onlyChild returns child element

What is the `render` function of a functional component?

* Add a test for rendering SVG into a non-React SVG tree

It is failing in Fiber.

* Add a test for rendering HTML into non-React foreignObject

It happens to pass in Fiber.

* Determine root namespace by container namespace, not just tag

A tag alone is not enough to determine the tree namespace.

* Skip the test that exhibits jsdom bug in non-createElement mode

jsdom doesn't give HTML namespace to foreignObject.innerHTML children.
This problem doesn't exist in the browsers.

#8638 (comment)

We will skip this test in non-createElement mode considering
that non-createElement mounting is effectively dead code now anyway.

Also removed an unnecessary conditional check and improved a flow cast.

Relates originally to PRs #8646 and #8685

A new module has been added (ReactFiberErrorLogger). This logs error information (call stack and component stack) to the console to make errors easier to debug. It also prompts users to use error boundaries if they are not already using them.

In the future, perhaps this will be injectable, enabling users to provide their own handler for custom processing/logging. For the time being, this should help with issues like this / #2461.

Added memoization test for interrupted low-priority renders

Test added to verify that a high-priority update can reuse the children from an aborted low-priority update if shouldComponentUpdate returns false.

Warn about missing getChildContext method

* Simplify the hooks
* Capture completion at the right moment
* Animate the scroll with the fiber on the stack
* Better display priorities

Previous (probably unintentional) behavior of Stack was to allow components to define childContextTypes without also supplying a getChildContext property. This PR updates Fiber to (temporarily) mimic that behavior. It also adds warning messages to both Fiber and Stack (along with a test).

For the time being, Fiber components with a missing getChildContext method will return the parent context as-is, after warning.

[Fiber] Move memoization to begin phase

Add feature flag to disable Fiber-only features

Fixes the case where there's an uncaught error and the root unmounts.
We implement this by rendering the root as if its child is null. Null is
not usually allowed at the top level, so we need to special case it.

Moved the top-level check to ReactChildFiber like the other ones

* Ignore orphaned fibers in the debugger

* Remember last entered code via localStorage

* Update Create React App

* Minor fixes

* Dogfood Fiber

Includes a test that confirms that work that is bailed out before
completing can be reused without dropping the entire subtree.