Merge branch 'master' into master

Author: taehwanno

Diff for: .github/PULL_REQUEST_TEMPLATE.md

@@ -1,5 +1,14 @@
+Note to Hacktoberfest 🎃 participants:
 
+While we appreciate the enthusiasm, we are experiencing a high volume of drive-by pull requests (one-line changes, README tweaks, etc.). Please remember that hundreds of people are subscribed to this repo and will receive notifications for these PRs. Spam submissions will be closed and won't count towards your Hacktoberfest goals.
 
+Please search for issues tagged [`good first issue`][gfi] or [`hacktoberfest`][hacktoberfest] to find things to work on.
+
+You can also search [all of GitHub][all].
+
+[gfi]: https://github.com/reactjs/reactjs.org/issues?q=is%3Aissue+is%3Aopen+label%3A"good+first+issue"
+[hacktoberfest]: https://github.com/reactjs/reactjs.org/issues?q=is%3Aissue+is%3Aopen+label%3A"good+first+issue"
+[all]: https://github.com/search?q=is%3Aissue+hacktoberfest
 <!--
 
 Thank you for the PR! Contributors like you keep React awesome!

Diff for: content/authors.yml

@@ -52,6 +52,9 @@ kmeht:
 LoukaN:
   name: Lou Husson
   url: https://twitter.com/loukan42
+lunaruan:
+  name: Luna Ruan
+  url: https://twitter.com/lunaruan
 matthewjohnston4:
   name: Matthew Johnston
   url: https://github.com/matthewathome

Diff for: content/blog/2016-07-11-introducing-reacts-error-code-system.md

@@ -9,7 +9,7 @@ Prior to this release, we stripped out error messages at build-time and this is
 
 > Minified exception occurred; use the non-minified dev environment for the full error message and additional helpful warnings.
 
-In order to make debugging in production easier, we're introducing an Error Code System in [15.2.0](https://github.com/facebook/react/releases/tag/v15.2.0). We developed a [gulp script](https://github.com/facebook/react/blob/master/scripts/error-codes/gulp-extract-errors.js) that collects all of our `invariant` error messages and folds them to a [JSON file](https://github.com/facebook/react/blob/master/scripts/error-codes/codes.json), and at build-time Babel uses the JSON to [rewrite](https://github.com/facebook/react/blob/master/scripts/error-codes/replace-invariant-error-codes.js) our `invariant` calls in production to reference the corresponding error IDs. Now when things go wrong in production, the error that React throws will contain a URL with an error ID and relevant information. The URL will point you to a page in our documentation where the original error message gets reassembled.
+In order to make debugging in production easier, we're introducing an Error Code System in [15.2.0](https://github.com/facebook/react/releases/tag/v15.2.0). We developed a [script](https://github.com/facebook/react/blob/master/scripts/error-codes/extract-errors.js) that collects all of our `invariant` error messages and folds them to a [JSON file](https://github.com/facebook/react/blob/master/scripts/error-codes/codes.json), and at build-time Babel uses the JSON to [rewrite](https://github.com/facebook/react/blob/master/scripts/error-codes/transform-error-messages.js) our `invariant` calls in production to reference the corresponding error IDs. Now when things go wrong in production, the error that React throws will contain a URL with an error ID and relevant information. The URL will point you to a page in our documentation where the original error message gets reassembled.
 
 While we hope you don't see errors often, you can see how it works [here](/docs/error-decoder.html?invariant=109&args[]=Foo). This is what the same error from above will look like:
 

Diff for: content/blog/2020-08-10-react-v17-rc.md

@@ -162,17 +162,17 @@ useEffect(() => {
 
 Most effects don't need to delay screen updates, so React runs them asynchronously soon after the update has been reflected on the screen. (For the rare cases where you need an effect to block paint, e.g. to measure and position a tooltip, prefer `useLayoutEffect`.)
 
-However, the effect *cleanup* function, when it exists, used to run synchronously in React 16. We've found that, similar to `componentWillUnmount` being synchronous in classes, this is not ideal for larger apps because it slows down large screen transitions (e.g. switching tabs).
+However, when a component is unmounting, effect *cleanup* functions used to run synchronously (similar to `componentWillUnmount` being synchronous in classes). We've found that this is not ideal for larger apps because it slows down large screen transitions (e.g. switching tabs).
 
-**In React 17, the effect cleanup function also runs asynchronously -- for example, if the component is unmounting, the cleanup will run _after_ the screen has been updated.**
+**In React 17, the effect cleanup function always runs asynchronously -- for example, if the component is unmounting, the cleanup runs _after_ the screen has been updated.**
 
-This mirrors how the effects themselves run more closely. In the  rare cases where you might want to rely on the synchronous execution, you can switch to `useLayoutEffect` instead.
+This mirrors how the effects themselves run more closely. In the rare cases where you might want to rely on the synchronous execution, you can switch to `useLayoutEffect` instead.
 
 >Note
 >
 >You might be wondering whether this means that you'll now be unable to fix warnings about `setState` on unmounted components. Don't worry -- React specifically checks for this case, and does *not* fire `setState` warnings in the short gap between unmounting and the cleanup. **So code cancelling requests or intervals can almost always stay the same.**
 
-Additionally, React 17 executes the cleanup functions in the same order as the effects, according to their position in the tree. Previously, this order was occasionally different.
+Additionally, React 17 will always execute all effect cleanup functions (for all components) before it runs any new effects. React 16 only guaranteed this ordering for effects within a component.
 
 #### Potential Issues {#potential-issues}
 
@@ -272,20 +272,20 @@ We encourage you to try React 17.0 Release Candidate soon and [raise any issues]
 To install React 17 RC with npm, run:
 
 ```bash
-npm install [email protected].0 [email protected].0
+npm install [email protected].3 [email protected].3
 ```
 
 To install React 17 RC with Yarn, run:
 
 ```bash
-yarn add [email protected].0 [email protected].0
+yarn add [email protected].3 [email protected].3
 ```
 
 We also provide UMD builds of React via a CDN:
 
 ```html
-<script crossorigin src="https://unpkg.com/[email protected].0/umd/react.production.min.js"></script>
-<script crossorigin src="https://unpkg.com/[email protected].0/umd/react-dom.production.min.js"></script>
+<script crossorigin src="https://unpkg.com/[email protected].3/umd/react.production.min.js"></script>
+<script crossorigin src="https://unpkg.com/[email protected].3/umd/react-dom.production.min.js"></script>
 ```
 
 Refer to the documentation for [detailed installation instructions](/docs/installation.html).
@@ -297,6 +297,8 @@ Refer to the documentation for [detailed installation instructions](/docs/instal
 * Add `react/jsx-runtime` and `react/jsx-dev-runtime` for the [new JSX transform](https://babeljs.io/blog/2020/03/16/7.9.0#a-new-jsx-transform-11154-https-githubcom-babel-babel-pull-11154). ([@lunaruan](https://github.com/lunaruan) in [#18299](https://github.com/facebook/react/pull/18299))
 * Build component stacks from native error frames. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18561](https://github.com/facebook/react/pull/18561))
 * Allow to specify `displayName` on context for improved stacks. ([@eps1lon](https://github.com/eps1lon) in [#18224](https://github.com/facebook/react/pull/18224))
+* Prevent `'use strict'` from leaking in the UMD bundles. ([@koba04](https://github.com/koba04) in [#19614](https://github.com/facebook/react/pull/19614))
+* Stop using `fb.me` for redirects. ([@cylim](https://github.com/cylim) in [#19598](https://github.com/facebook/react/pull/19598))
 
 ### React DOM {#react-dom}
 
@@ -309,6 +311,7 @@ Refer to the documentation for [detailed installation instructions](/docs/instal
 * Throw if `forwardRef` or `memo` component returns `undefined`. ([@gaearon](https://github.com/gaearon) in [#19550](https://github.com/facebook/react/pull/19550))
 * Remove event pooling. ([@trueadm](https://github.com/trueadm) in [#18969](https://github.com/facebook/react/pull/18969))
 * Stop exposing internals that won’t be needed by React Native Web. ([@necolas](https://github.com/necolas) in [#18483](https://github.com/facebook/react/pull/18483))
+* Attach all known event listeners when the root mounts. ([@gaearon](https://github.com/gaearon) in [#19659](https://github.com/facebook/react/pull/19659))
 * Disable `console` in the second render pass of DEV mode double render. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18547](https://github.com/facebook/react/pull/18547))
 * Deprecate the undocumented and misleading `ReactTestUtils.SimulateNative` API. ([@gaearon](https://github.com/gaearon) in [#13407](https://github.com/facebook/react/pull/13407))
 * Rename private field names used in the internals. ([@gaearon](https://github.com/gaearon) in [#18377](https://github.com/facebook/react/pull/18377))
@@ -324,11 +327,16 @@ Refer to the documentation for [detailed installation instructions](/docs/instal
 * Improve the error message for invalid updates. ([@JoviDeCroock](https://github.com/JoviDeCroock) in [#18316](https://github.com/facebook/react/pull/18316))
 * Exclude forwardRef and memo from stack frames. ([@sebmarkbage](https://github.com/sebmarkbage) in [#18559](https://github.com/facebook/react/pull/18559))
 * Improve the error message when switching between controlled and uncontrolled inputs. ([@vcarl](https://github.com/vcarl) in [#17070](https://github.com/facebook/react/pull/17070))
+* Keep `onTouchStart`, `onTouchMove`, and `onWheel` passive. ([@gaearon](https://github.com/gaearon) in [#19654](https://github.com/facebook/react/pull/19654))
 * Fix `setState` hanging in development inside a closed iframe. ([@gaearon](https://github.com/gaearon) in [#19220](https://github.com/facebook/react/pull/19220))
 * Fix rendering bailout for lazy components with `defaultProps`. ([@jddxf](https://github.com/jddxf) in [#18539](https://github.com/facebook/react/pull/18539))
 * Fix a false positive warning when `dangerouslySetInnerHTML` is `undefined`. ([@eps1lon](https://github.com/eps1lon) in [#18676](https://github.com/facebook/react/pull/18676))
 * Fix Test Utils with non-standard `require` implementation. ([@just-boris](https://github.com/just-boris) in [#18632](https://github.com/facebook/react/pull/18632))
 * Fix `onBeforeInput` reporting an incorrect `event.type`. ([@eps1lon](https://github.com/eps1lon) in [#19561](https://github.com/facebook/react/pull/19561))
+* Fix `event.relatedTarget` reported as `undefined` in Firefox. ([@claytercek](https://github.com/claytercek) in [#19607](https://github.com/facebook/react/pull/19607))
+* Fix "unspecified error" in IE11. ([@hemakshis](https://github.com/hemakshis) in [#19664](https://github.com/facebook/react/pull/19664))
+* Fix rendering into a shadow root. ([@Jack-Works](https://github.com/Jack-Works) in [#15894](https://github.com/facebook/react/pull/15894))
+* Fix `movementX/Y` polyfill with capture events. ([@gaearon](https://github.com/gaearon) in [#19672](https://github.com/facebook/react/pull/19672))
 * Use delegation for `onSubmit` and `onReset` events. ([@gaearon](https://github.com/gaearon) in [#19333](https://github.com/facebook/react/pull/19333))
 * Improve memory usage. ([@trueadm](https://github.com/trueadm) in [#18970](https://github.com/facebook/react/pull/18970))
 
@@ -346,9 +354,13 @@ Refer to the documentation for [detailed installation instructions](/docs/instal
 * Revamp the priority batching heuristics. ([@acdlite](https://github.com/acdlite) in [#18796](https://github.com/facebook/react/pull/18796))
 * Add the `unstable_` prefix before the experimental APIs. ([@acdlite](https://github.com/acdlite) in [#18825](https://github.com/facebook/react/pull/18825))
 * Remove `unstable_discreteUpdates` and `unstable_flushDiscreteUpdates`. ([@trueadm](https://github.com/trueadm) in [#18825](https://github.com/facebook/react/pull/18825))
+* Remove the `timeoutMs` argument. ([@acdlite](https://github.com/acdlite) in [#19703](https://github.com/facebook/react/pull/19703))
 * Disable `<div hidden />` prerendering in favor of a different future API. ([@acdlite](https://github.com/acdlite) in [#18917](https://github.com/facebook/react/pull/18917))
+* Add `unstable_expectedLoadTime` to Suspense for CPU-bound trees. ([@acdlite](https://github.com/acdlite) in [#19936](https://github.com/facebook/react/pull/19936))
 * Add an experimental `unstable_useOpaqueIdentifier` Hook. ([@lunaruan](https://github.com/lunaruan) in [#17322](https://github.com/facebook/react/pull/17322))
+* Add an experimental `unstable_startTransition` API. ([@rickhanlonii](https://github.com/rickhanlonii) in [#19696](https://github.com/facebook/react/pull/19696))
 * Using `act` in the test renderer no longer flushes Suspense fallbacks. ([@acdlite](https://github.com/acdlite) in [#18596](https://github.com/facebook/react/pull/18596))
+* Use global render timeout for CPU Suspense. ([@sebmarkbage](https://github.com/sebmarkbage) in [#19643](https://github.com/facebook/react/pull/19643))
 * Clear the existing root content before mounting. ([@bvaughn](https://github.com/bvaughn) in [#18730](https://github.com/facebook/react/pull/18730))
 * Fix a bug with error boundaries. ([@acdlite](https://github.com/acdlite) in [#18265](https://github.com/facebook/react/pull/18265))
 * Fix a bug causing dropped updates in a suspended tree. ([@acdlite](https://github.com/acdlite) in [#18384](https://github.com/facebook/react/pull/18384) and [#18457](https://github.com/facebook/react/pull/18457))