useFormState: Emit comment to mark whether state matches #27307
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gnoff
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| if (getIsHydrating()) { | ||
| // TODO: If this function returns true, it means we should use the form | ||
| // state passed to hydrateRoot instead of initialState. | ||
| tryToClaimNextHydratableFormMarkerInstance(currentlyRenderingFiber); | ||
| } |
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This hydrating gate and the one in tryToClaim... are redundant. I assume there will be other logic in here so probably can drop the one in tryTo...
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Yeah I did it that way to match the other similar functions in that file, which all have the guard at the top and also is redundant because the callers usually end up checking it regardless. Usually if I'm not the one who wrote a module I copy the style of the surrounding code for 1) consistency because I figure if I fix it here I should also fix it everywhere else 2) out of caution in case there was a good reason that I'm not thinking of :D
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| export function canHydrateFormStateMarker( | ||
| instance: HydratableInstance, | ||
| ): null | FormStateMarkerInstance { | ||
| const nodeData = (instance: any).data; | ||
| if ( | ||
| nodeData === FORM_STATE_IS_MATCHING || | ||
| nodeData === FORM_STATE_IS_NOT_MATCHING | ||
| ) { | ||
| const markerInstance: FormStateMarkerInstance = (instance: any); | ||
| return markerInstance; | ||
| } | ||
| return null; | ||
| } |
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There is this unfortunate forking of behavior in the canHydrate... functions where if we are in a Singleton like <body> or are in the container scope we assume there may be 3rd party nodes we need to skip over. If our nextHydratable was some injected 3rd party stylesheet then hydration would fail as this is currently implemented. I think this function needs. a similar treatment as canHydrateSuspenseInstance
This will make your optimization where we omit the marker when the hook is normal harder too b/c it'll need to be able to scan forward but also jump back to where it was if it doesn't find anything
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Re: the last point about the optimization, the idea is we wouldn't look for these nodes at all in that case. Basically it would revert to how it is today.
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hmm I think this would still be a problem
function App() {
... = useFormState();
return <div>...</div>
}
<script injectedBy3rdParty />
<!--!F-->
<div>
...
</div>
If I'm hydrating App the nextHydratableInstance will end up on <script injectedBy3rdParty /> Then when we check whether there is a form marker we see there isn't and we assume no postback state. Then we try to claim the next hydratable for <div>. We end up hitting the form state marker and stop causing a hydration mismatch.
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yeah that part makes sense, I just mean in the case where there's no postback state, there are no extra comment nodes at all, so all this code gets skipped anyway
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| if (bufferedChunks !== null) { | ||
| // This component emitted some chunks. They are buffered until it finishes | ||
| // rendering successfully. We can flush them now. | ||
| const task: Task = (currentlyRenderingTask: any); | ||
| const target = task.blockedSegment.chunks; | ||
| // Not sure why Flow complains. If I change it to spread instead of apply, | ||
| // it checks fine. | ||
| // $FlowFixMe[method-unbinding] | ||
| target.push.apply(target, bufferedChunks); | ||
| } |
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I'm not sure this is going to work in the edge case
function App() {
let ... = useFormState();
return (
<html>
<body>
<form ...>
</body>
</html>
}
In Fizz (with float enabled) the html chunks are sequester so the fact that the comment is getting pushed to the target before the DOCTYPE does accidentally works out (we'll still emit <DOCTYPE html><html><head><!--F-->). However when hydrating on the client the starting point for hydration is document.body I believe (I can't remember if I made this change or I just talked about making it but conceptually we can start hydration from body b/c everything else is singleton which has it's own hydration path). If hydration starts from the body the form comment will be missed b/c it is in the head.
I don't have a good solution to this problem. We could maybe figure out if we need to put the comment before the <html> in the DOM by slotting it just after the DOCTYPE. Then we'd have to also special case the hydration cursor to look there. Additionally I think this may conflict with prerendering b/c we will have a static preamble (the html, head tag, and some head content) even when we can't fully prerender the entire shell. So we may have something dynamic (the form state indictator comment) that needs to be embedded inside the static part which just can't happen
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Another crude way to do it could be to forbid useFormState outside of the body 😆
sebmarkbage
reviewed
Aug 30, 2023
| @@ -187,6 +193,8 @@ const SUSPENSE_START_DATA = '$'; | |||
| const SUSPENSE_END_DATA = '/$'; | |||
| const SUSPENSE_PENDING_START_DATA = '$?'; | |||
| const SUSPENSE_FALLBACK_START_DATA = '$!'; | |||
| const FORM_STATE_IS_MATCHING = '!F'; | |||
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Nit: I understand you're using this to mean NOT form state but the pattern that the other signaling comments use is:
TAG + STATE
So you can just check the first character to see if it matches the type of thing and then the second character is the state of that thing.
We should probably stick to that pattern. In theory if we did like switch(data[0]) it could matter.
sebmarkbage
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Aug 30, 2023
| @@ -187,6 +193,8 @@ const SUSPENSE_START_DATA = '$'; | |||
| const SUSPENSE_END_DATA = '/$'; | |||
| const SUSPENSE_PENDING_START_DATA = '$?'; | |||
| const SUSPENSE_FALLBACK_START_DATA = '$!'; | |||
| const FORM_STATE_IS_MATCHING = '!F'; | |||
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Suggested change
| const FORM_STATE_IS_MATCHING = '!F'; | |
| const FORM_STATE_IS_MATCHING = 'F!'; |
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A planned feature of useFormState is that if page load is the result of an MPA-style form submission — i.e. a form was submitted before it was hydrated, using Server Actions — the state should transfer to the next page. I haven't implemented that part yet, but as a prerequisite, we need some way for Fizz to indicate whether a useFormState hook was rendered using the "postback" state. That way we can do all state matching logic on the server without having to replicate it on the client, too. The approach here is to emit a comment node for each useFormState hook. We use one of two comment types: `<!--F-->` for a normal useFormState hook, and `<!--F!-->` for a hook that was rendered using the postback state. React will read these markers during hydration. This is similar to how we encode Suspense boundaries. Again, the actual matching algorithm is not yet implemented — for now, the "not matching" marker is always emitted. We can optimize this further by not emitting any markers for a render that is not the result of a form postback, which I'll do in subsequent PRs.
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A planned feature of useFormState is that if the page load is the result of an MPA-style form submission — i.e. a form was submitted before it was hydrated, using Server Actions — the state of the hook should transfer to the next page. I haven't implemented that part yet, but as a prerequisite, we need some way for Fizz to indicate whether a useFormState hook was rendered using the "postback" state. That way we can do all state matching logic on the server without having to replicate it on the client, too. The approach here is to emit a comment node for each useFormState hook. We use one of two comment types: `<!--F-->` for a normal useFormState hook, and `<!--F!-->` for a hook that was rendered using the postback state. React will read these markers during hydration. This is similar to how we encode Suspense boundaries. Again, the actual matching algorithm is not yet implemented — for now, the "not matching" marker is always emitted. We can optimize this further by not emitting any markers for a render that is not the result of a form postback, which I'll do in subsequent PRs. DiffTrain build for [8b26f07](8b26f07)
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React upstream changes: - facebook/react#27374 - facebook/react#27369 - facebook/react#27372 - facebook/react#27371 - facebook/react#27370 - facebook/react#27321 - facebook/react#27368 - facebook/react#27367 - facebook/react#27366 - facebook/react#27360 - facebook/react#27361 - facebook/react#27357 - facebook/react#27359 - facebook/react#27358 - facebook/react#27330 - facebook/react#27347 - facebook/react#27307 - facebook/react#27346 - facebook/react#27342 - facebook/react#27340 - facebook/react#27328 - facebook/react#27327 - facebook/react#27325 - facebook/react#27337 - facebook/react#27336 - facebook/react#27323 - facebook/react#27320 - facebook/react#27317 - facebook/react#27318 - facebook/react#27316 - facebook/react#27313 - facebook/react#27309 - facebook/react#27302 - facebook/react#27297 - facebook/react#27295 - facebook/react#27305 - facebook/react#27215 - facebook/react#27304 - facebook/react#27067 - facebook/react#27179 - facebook/react#27278 - facebook/react#27277 - facebook/react#27282 - facebook/react#27230 - facebook/react#27260 - facebook/react#27270 - facebook/react#27273 - facebook/react#27268 - facebook/react#27269
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React upstream changes: - facebook/react#27374 - facebook/react#27369 - facebook/react#27372 - facebook/react#27371 - facebook/react#27370 - facebook/react#27321 - facebook/react#27368 - facebook/react#27367 - facebook/react#27366 - facebook/react#27360 - facebook/react#27361 - facebook/react#27357 - facebook/react#27359 - facebook/react#27358 - facebook/react#27330 - facebook/react#27347 - facebook/react#27307 - facebook/react#27346 - facebook/react#27342 - facebook/react#27340 - facebook/react#27328 - facebook/react#27327 - facebook/react#27325 - facebook/react#27337 - facebook/react#27336 - facebook/react#27323 - facebook/react#27320 - facebook/react#27317 - facebook/react#27318 - facebook/react#27316 - facebook/react#27313 - facebook/react#27309 - facebook/react#27302 - facebook/react#27297 - facebook/react#27295 - facebook/react#27305 - facebook/react#27215 - facebook/react#27304 - facebook/react#27067 - facebook/react#27179 - facebook/react#27278 - facebook/react#27277 - facebook/react#27282 - facebook/react#27230 - facebook/react#27260 - facebook/react#27270 - facebook/react#27273 - facebook/react#27268 - facebook/react#27269
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React upstream changes: - facebook/react#27374 - facebook/react#27369 - facebook/react#27372 - facebook/react#27371 - facebook/react#27370 - facebook/react#27321 - facebook/react#27368 - facebook/react#27367 - facebook/react#27366 - facebook/react#27360 - facebook/react#27361 - facebook/react#27357 - facebook/react#27359 - facebook/react#27358 - facebook/react#27330 - facebook/react#27347 - facebook/react#27307 - facebook/react#27346 - facebook/react#27342 - facebook/react#27340 - facebook/react#27328 - facebook/react#27327 - facebook/react#27325 - facebook/react#27337 - facebook/react#27336 - facebook/react#27323 - facebook/react#27320 - facebook/react#27317 - facebook/react#27318 - facebook/react#27316 - facebook/react#27313 - facebook/react#27309 - facebook/react#27302 - facebook/react#27297 - facebook/react#27295 - facebook/react#27305 - facebook/react#27215 - facebook/react#27304 - facebook/react#27067 - facebook/react#27179 - facebook/react#27278 - facebook/react#27277 - facebook/react#27282 - facebook/react#27230 - facebook/react#27260 - facebook/react#27270 - facebook/react#27273 - facebook/react#27268 - facebook/react#27269
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### React upstream changes: - facebook/react#27374 - facebook/react#27369 - facebook/react#27372 - facebook/react#27371 - facebook/react#27370 - facebook/react#27321 - facebook/react#27368 - facebook/react#27367 - facebook/react#27366 - facebook/react#27360 - facebook/react#27361 - facebook/react#27357 - facebook/react#27359 - facebook/react#27358 - facebook/react#27330 - facebook/react#27347 - facebook/react#27307 - facebook/react#27346 - facebook/react#27342 - facebook/react#27340 - facebook/react#27328 - facebook/react#27327 - facebook/react#27325 - facebook/react#27337 - facebook/react#27336 - facebook/react#27323 - facebook/react#27320 - facebook/react#27317 - facebook/react#27318 - facebook/react#27316 - facebook/react#27313 - facebook/react#27309 - facebook/react#27302 - facebook/react#27297 - facebook/react#27295 - facebook/react#27305 - facebook/react#27215 - facebook/react#27304 - facebook/react#27067 - facebook/react#27179 - facebook/react#27278 - facebook/react#27277 - facebook/react#27282 - facebook/react#27230 - facebook/react#27260 - facebook/react#27270 - facebook/react#27273 - facebook/react#27268 - facebook/react#27269
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) A planned feature of useFormState is that if the page load is the result of an MPA-style form submission — i.e. a form was submitted before it was hydrated, using Server Actions — the state of the hook should transfer to the next page. I haven't implemented that part yet, but as a prerequisite, we need some way for Fizz to indicate whether a useFormState hook was rendered using the "postback" state. That way we can do all state matching logic on the server without having to replicate it on the client, too. The approach here is to emit a comment node for each useFormState hook. We use one of two comment types: `<!--F-->` for a normal useFormState hook, and `<!--F!-->` for a hook that was rendered using the postback state. React will read these markers during hydration. This is similar to how we encode Suspense boundaries. Again, the actual matching algorithm is not yet implemented — for now, the "not matching" marker is always emitted. We can optimize this further by not emitting any markers for a render that is not the result of a form postback, which I'll do in subsequent PRs.
bigfootjon
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A planned feature of useFormState is that if the page load is the result of an MPA-style form submission — i.e. a form was submitted before it was hydrated, using Server Actions — the state of the hook should transfer to the next page. I haven't implemented that part yet, but as a prerequisite, we need some way for Fizz to indicate whether a useFormState hook was rendered using the "postback" state. That way we can do all state matching logic on the server without having to replicate it on the client, too. The approach here is to emit a comment node for each useFormState hook. We use one of two comment types: `<!--F-->` for a normal useFormState hook, and `<!--F!-->` for a hook that was rendered using the postback state. React will read these markers during hydration. This is similar to how we encode Suspense boundaries. Again, the actual matching algorithm is not yet implemented — for now, the "not matching" marker is always emitted. We can optimize this further by not emitting any markers for a render that is not the result of a form postback, which I'll do in subsequent PRs. DiffTrain build for commit 8b26f07.
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This PR contains the following updates:
| Package | Type | Update | Change |
|---|---|---|---|
| [@types/react](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/react) ([source](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/react)) | devDependencies | major | [`18.3.18` -> `19.0.7`](https://renovatebot.com/diffs/npm/@types%2freact/18.3.18/19.0.7) |
| [@types/react-dom](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/react-dom) ([source](https://github.com/DefinitelyTyped/DefinitelyTyped/tree/HEAD/types/react-dom)) | devDependencies | major | [`18.3.5` -> `19.0.3`](https://renovatebot.com/diffs/npm/@types%2freact-dom/18.3.5/19.0.3) |
| [react](https://react.dev/) ([source](https://github.com/facebook/react/tree/HEAD/packages/react)) | dependencies | major | [`18.3.1` -> `19.0.0`](https://renovatebot.com/diffs/npm/react/18.3.1/19.0.0) |
| [react-dom](https://react.dev/) ([source](https://github.com/facebook/react/tree/HEAD/packages/react-dom)) | dependencies | major | [`18.3.1` -> `19.0.0`](https://renovatebot.com/diffs/npm/react-dom/18.3.1/19.0.0) |
---
### Release Notes
<details>
<summary>facebook/react (react)</summary>
### [`v19.0.0`](https://github.com/facebook/react/blob/HEAD/CHANGELOG.md#1900-December-5-2024)
[Compare Source](https://github.com/facebook/react/compare/v18.3.1...v19.0.0)
Below is a list of all new features, APIs, deprecations, and breaking changes. Read [React 19 release post](https://react.dev/blog/2024/04/25/react-19) and [React 19 upgrade guide](https://react.dev/blog/2024/04/25/react-19-upgrade-guide) for more information.
> Note: To help make the upgrade to React 19 easier, we’ve published a react@18.3 release that is identical to 18.2 but adds warnings for deprecated APIs and other changes that are needed for React 19. We recommend upgrading to React 18.3.1 first to help identify any issues before upgrading to React 19.
##### New Features
##### React
- Actions: `startTransition` can now accept async functions. Functions passed to `startTransition` are called “Actions”. A given Transition can include one or more Actions which update state in the background and update the UI with one commit. In addition to updating state, Actions can now perform side effects including async requests, and the Action will wait for the work to finish before finishing the Transition. This feature allows Transitions to include side effects like `fetch()` in the pending state, and provides support for error handling, and optimistic updates.
- `useActionState`: is a new hook to order Actions inside of a Transition with access to the state of the action, and the pending state. It accepts a reducer that can call Actions, and the initial state used for first render. It also accepts an optional string that is used if the action is passed to a form `action` prop to support progressive enhancement in forms.
- `useOptimistic`: is a new hook to update state while a Transition is in progress. It returns the state, and a set function that can be called inside a transition to “optimistically” update the state to expected final value immediately while the Transition completes in the background. When the transition finishes, the state is updated to the new value.
- `use`: is a new API that allows reading resources in render. In React 19, `use` accepts a promise or Context. If provided a promise, `use` will suspend until a value is resolved. `use` can only be used in render but can be called conditionally.
- `ref` as a prop: Refs can now be used as props, removing the need for `forwardRef`.
- **Suspense sibling pre-warming**: When a component suspends, React will immediately commit the fallback of the nearest Suspense boundary, without waiting for the entire sibling tree to render. After the fallback commits, React will schedule another render for the suspended siblings to “pre-warm” lazy requests.
##### React DOM Client
- `<form> action` prop: Form Actions allow you to manage forms automatically and integrate with `useFormStatus`. When a `<form> action` succeeds, React will automatically reset the form for uncontrolled components. The form can be reset manually with the new `requestFormReset` API.
- `<button> and <input> formAction` prop: Actions can be passed to the `formAction` prop to configure form submission behavior. This allows using different Actions depending on the input.
- `useFormStatus`: is a new hook that provides the status of the parent `<form> action`, as if the form was a Context provider. The hook returns the values: `pending`, `data`, `method`, and `action`.
- Support for Document Metadata: We’ve added support for rendering document metadata tags in components natively. React will automatically hoist them into the `<head>` section of the document.
- Support for Stylesheets: React 19 will ensure stylesheets are inserted into the `<head>` on the client before revealing the content of a Suspense boundary that depends on that stylesheet.
- Support for async scripts: Async scripts can be rendered anywhere in the component tree and React will handle ordering and deduplication.
- Support for preloading resources: React 19 ships with `preinit`, `preload`, `prefetchDNS`, and `preconnect` APIs to optimize initial page loads by moving discovery of additional resources like fonts out of stylesheet loading. They can also be used to prefetch resources used by an anticipated navigation.
##### React DOM Server
- Added `prerender` and `prerenderToNodeStream` APIs for static site generation. They are designed to work with streaming environments like Node.js Streams and Web Streams. Unlike `renderToString`, they wait for data to load for HTML generation.
##### React Server Components
- RSC features such as directives, server components, and server functions are now stable. This means libraries that ship with Server Components can now target React 19 as a peer dependency with a react-server export condition for use in frameworks that support the Full-stack React Architecture. The underlying APIs used to implement a React Server Components bundler or framework do not follow semver and may break between minors in React 19.x. See [docs](https://19.react.dev/reference/rsc/server-components) for how to support React Server Components.
##### Deprecations
- Deprecated: `element.ref` access: React 19 supports ref as a prop, so we’re deprecating `element.ref` in favor of `element.props.ref`. Accessing will result in a warning.
- `react-test-renderer`: In React 19, react-test-renderer logs a deprecation warning and has switched to concurrent rendering for web usage. We recommend migrating your tests to [@​testing-library/react](https://testing-library.com/docs/react-testing-library/intro/) or [@​testing-library/react-native](https://testing-library.com/docs/react-native-testing-library/intro)
##### Breaking Changes
React 19 brings in a number of breaking changes, including the removals of long-deprecated APIs. We recommend first upgrading to `18.3.1`, where we've added additional deprecation warnings. Check out the [upgrade guide](https://19.react.dev/blog/2024/04/25/react-19-upgrade-guide) for more details and guidance on codemodding.
##### React
- New JSX Transform is now required: We introduced [a new JSX transform](https://legacy.reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html) in 2020 to improve bundle size and use JSX without importing React. In React 19, we’re adding additional improvements like using ref as a prop and JSX speed improvements that require the new transform.
- Errors in render are not re-thrown: Errors that are not caught by an Error Boundary are now reported to window.reportError. Errors that are caught by an Error Boundary are reported to console.error. We’ve introduced `onUncaughtError` and `onCaughtError` methods to `createRoot` and `hydrateRoot` to customize this error handling.
- Removed: `propTypes`: Using `propTypes` will now be silently ignored. If required, we recommend migrating to TypeScript or another type-checking solution.
- Removed: `defaultProps` for functions: ES6 default parameters can be used in place. Class components continue to support `defaultProps` since there is no ES6 alternative.
- Removed: `contextTypes` and `getChildContext`: Legacy Context for class components has been removed in favor of the `contextType` API.
- Removed: string refs: Any usage of string refs need to be migrated to ref callbacks.
- Removed: Module pattern factories: A rarely used pattern that can be migrated to regular functions.
- Removed: `React.createFactory`: Now that JSX is broadly supported, all `createFactory` usage can be migrated to JSX components.
- Removed: `react-test-renderer/shallow`: This has been a re-export of [react-shallow-renderer](https://github.com/enzymejs/react-shallow-renderer) since React 18. If needed, you can continue to use the third-party package directly. We recommend using [@​testing-library/react](https://testing-library.com/docs/react-testing-library/intro/) or [@​testing-library/react-native](https://testing-library.com/docs/react-native-testing-library/intro) instead.
##### React DOM
- Removed: `react-dom/test-utils`: We’ve moved `act` from `react-dom/test-utils` to react. All other utilities have been removed.
- Removed: `ReactDOM`.`render`, `ReactDOM`.`hydrate`: These have been removed in favor of the concurrent equivalents: `ReactDOM`.`createRoot` and `ReactDOM.hydrateRoot`.
- Removed: `unmountComponentAtNode`: Removed in favor of `root.unmount()`.
- Removed: `ReactDOM`.`findDOMNode`: You can replace `ReactDOM`.`findDOMNode` with DOM Refs.
##### Notable Changes
##### React
- `<Context>` as a provider: You can now render `<Context>` as a provider instead of `<Context.Provider>`.
- Cleanup functions for refs: When the component unmounts, React will call the cleanup function returned from the ref callback.
- `useDeferredValue` initial value argument: When provided, `useDeferredValue` will return the initial value for the initial render of a component, then schedule a re-render in the background with the `deferredValue` returned.
- Support for Custom Elements: React 19 now passes all tests on [Custom Elements Everywhere](https://custom-elements-everywhere.com/).
- StrictMode changes: `useMemo` and `useCallback` will now reuse the memoized results from the first render, during the second render. Additionally, StrictMode will now double-invoke ref callback functions on initial mount.
- UMD builds removed: To load React 19 with a script tag, we recommend using an ESM-based CDN such as [esm.sh](http://esm.sh).
##### React DOM
- Diffs for hydration errors: In the case of a mismatch, React 19 logs a single error with a diff of the mismatched content.
- Compatibility with third-party scripts and extensions: React will now force a client re-render to fix up any mismatched content caused by elements inserted by third-party JS.
##### TypeScript Changes
The most common changes can be codemodded with `npx types-react-codemod@latest preset-19 ./path-to-your-react-ts-files`.
- Removed deprecated TypeScript types:
- `ReactChild` (replacement: `React.ReactElement | number | string)`
- `ReactFragment` (replacement: `Iterable<React.ReactNode>`)
- `ReactNodeArray` (replacement: `ReadonlyArray<React.ReactNode>`)
- `ReactText` (replacement: `number | string`)
- `VoidFunctionComponent` (replacement: `FunctionComponent`)
- `VFC` (replacement: `FC`)
- Moved to `prop-types`: `Requireable`, `ValidationMap`, `Validator`, `WeakValidationMap`
- Moved to `create-react-class`: `ClassicComponentClass`, `ClassicComponent`, `ClassicElement`, `ComponentSpec`, `Mixin`, `ReactChildren`, `ReactHTML`, `ReactSVG`, `SFCFactory`
- Disallow implicit return in refs: refs can now accept cleanup functions. When you return something else, we can’t tell if you intentionally returned something not meant to clean up or returned the wrong value. Implicit returns of anything but functions will now error.
- Require initial argument to `useRef`: The initial argument is now required to match `useState`, `createContext` etc
- Refs are mutable by default: Ref objects returned from `useRef()` are now always mutable instead of sometimes being immutable. This feature was too confusing for users and conflicted with legit cases where refs were managed by React and manually written to.
- Strict `ReactElement` typing: The props of React elements now default to `unknown` instead of `any` if the element is typed as `ReactElement`
- JSX namespace in TypeScript: The global `JSX` namespace is removed to improve interoperability with other libraries using JSX. Instead, the JSX namespace is available from the React package: `import { JSX } from 'react'`
- Better `useReducer` typings: Most `useReducer` usage should not require explicit type arguments.\
For example,
```diff
-useReducer<React.Reducer<State, Action>>(reducer)
+useReducer(reducer)
```
or
```diff
-useReducer<React.Reducer<State, Action>>(reducer)
+useReducer<State, Action>(reducer)
```
##### All Changes
##### React
- Add support for async Actions ([#​26621](https://github.com/facebook/react/pull/26621), [#​26726](https://github.com/facebook/react/pull/26726), [#​28078](https://github.com/facebook/react/pull/28078), [#​28097](https://github.com/facebook/react/pull/28097), [#​29226](https://github.com/facebook/react/pull/29226), [#​29618](https://github.com/facebook/react/pull/29618), [#​29670](https://github.com/facebook/react/pull/29670), [#​26716](https://github.com/facebook/react/pull/26716) by [@​acdlite](https://github.com/acdlite) and [@​sebmarkbage](https://github.com/sebmarkbage))
- Add `useActionState()` hook to update state based on the result of a Form Action ([#​27270](https://github.com/facebook/react/pull/27270), [#​27278](https://github.com/facebook/react/pull/27278), [#​27309](https://github.com/facebook/react/pull/27309), [#​27302](https://github.com/facebook/react/pull/27302), [#​27307](https://github.com/facebook/react/pull/27307), [#​27366](https://github.com/facebook/react/pull/27366), [#​27370](https://github.com/facebook/react/pull/27370), [#​27321](https://github.com/facebook/react/pull/27321), [#​27374](https://github.com/facebook/react/pull/27374), [#​27372](https://github.com/facebook/react/pull/27372), [#​27397](https://github.com/facebook/react/pull/27397), [#​27399](https://github.com/facebook/react/pull/27399), [#​27460](https://github.com/facebook/react/pull/27460), [#​28557](https://github.com/facebook/react/pull/28557), [#​27570](https://github.com/facebook/react/pull/27570), [#​27571](https://github.com/facebook/react/pull/27571), [#​28631](https://github.com/facebook/react/pull/28631), [#​28788](https://github.com/facebook/react/pull/28788), [#​29694](https://github.com/facebook/react/pull/29694), [#​29695](https://github.com/facebook/react/pull/29695), [#​29694](https://github.com/facebook/react/pull/29694), [#​29665](https://github.com/facebook/react/pull/29665), [#​28232](https://github.com/facebook/react/pull/28232), [#​28319](https://github.com/facebook/react/pull/28319) by [@​acdlite](https://github.com/acdlite), [@​eps1lon](https://github.com/eps1lon), and [@​rickhanlonii](https://github.com/rickhanlonii))
- Add `use()` API to read resources in render ([#​25084](https://github.com/facebook/react/pull/25084), [#​25202](https://github.com/facebook/react/pull/25202), [#​25207](https://github.com/facebook/react/pull/25207), [#​25214](https://github.com/facebook/react/pull/25214), [#​25226](https://github.com/facebook/react/pull/25226), [#​25247](https://github.com/facebook/react/pull/25247), [#​25539](https://github.com/facebook/react/pull/25539), [#​25538](https://github.com/facebook/react/pull/25538), [#​25537](https://github.com/facebook/react/pull/25537), [#​25543](https://github.com/facebook/react/pull/25543), [#​25561](https://github.com/facebook/react/pull/25561), [#​25620](https://github.com/facebook/react/pull/25620), [#​25615](https://github.com/facebook/react/pull/25615), [#​25922](https://github.com/facebook/react/pull/25922), [#​25641](https://github.com/facebook/react/pull/25641), [#​25634](https://github.com/facebook/react/pull/25634), [#​26232](https://github.com/facebook/react/pull/26232), [#​26536](https://github.com/facebook/react/pull/26535), [#​26739](https://github.com/facebook/react/pull/26739), [#​28233](https://github.com/facebook/react/pull/28233) by [@​acdlite](https://github.com/acdlite), [@​MofeiZ](https://github.com/mofeiZ), [@​sebmarkbage](https://github.com/sebmarkbage), [@​sophiebits](https://github.com/sophiebits), [@​eps1lon](https://github.com/eps1lon), and [@​hansottowirtz](https://github.com/hansottowirtz))
- Add `useOptimistic()` hook to display mutated state optimistically during an async mutation ([#​26740](https://github.com/facebook/react/pull/26740), [#​26772](https://github.com/facebook/react/pull/26772), [#​27277](https://github.com/facebook/react/pull/27277), [#​27453](https://github.com/facebook/react/pull/27453), [#​27454](https://github.com/facebook/react/pull/27454), [#​27936](https://github.com/facebook/react/pull/27936) by [@​acdlite](https://github.com/acdlite))
- Added an `initialValue` argument to `useDeferredValue()` hook ([#​27500](https://github.com/facebook/react/pull/27500), [#​27509](https://github.com/facebook/react/pull/27509), [#​27512](https://github.com/facebook/react/pull/27512), [#​27888](https://github.com/facebook/react/pull/27888), [#​27550](https://github.com/facebook/react/pull/27550) by [@​acdlite](https://github.com/acdlite))
- Support refs as props, warn on `element.ref` access ([#​28348](https://github.com/facebook/react/pull/28348), [#​28464](https://github.com/facebook/react/pull/28464), [#​28731](https://github.com/facebook/react/pull/28731) by [@​acdlite](https://github.com/acdlite))
- Support Custom Elements ([#​22184](https://github.com/facebook/react/pull/22184), [#​26524](https://github.com/facebook/react/pull/26524), [#​26523](https://github.com/facebook/react/pull/26523), [#​27511](https://github.com/facebook/react/pull/27511), [#​24541](https://github.com/facebook/react/pull/24541) by [@​josepharhar](https://github.com/josepharhar), [@​sebmarkbage](https://github.com/sebmarkbage), [@​gnoff](https://github.com/gnoff) and [@​eps1lon](https://github.com/eps1lon))
- Add ref cleanup function ([#​25686](https://github.com/facebook/react/pull/25686), [#​28883](https://github.com/facebook/react/pull/28883), [#​28910](https://github.com/facebook/react/pull/28910) by [@​sammy-SC](https://github.com/sammy-SC), [@​jackpope](https://github.com/jackpope), and [@​kassens](https://github.com/kassens))
- Sibling pre-rendering replaced by sibling pre-warming ([#​26380](https://github.com/facebook/react/pull/26380), [#​26549](https://github.com/facebook/react/pull/26549), [#​30761](https://github.com/facebook/react/pull/30761), [#​30800](https://github.com/facebook/react/pull/30800), [#​30762](https://github.com/facebook/react/pull/30762), [#​30879](https://github.com/facebook/react/pull/30879), [#​30934](https://github.com/facebook/react/pull/30934), [#​30952](https://github.com/facebook/react/pull/30952), [#​31056](https://github.com/facebook/react/pull/31056), [#​31452](https://github.com/facebook/react/pull/31452) by [@​sammy-SC](https://github.com/sammy-SC), [@​acdlite](https://github.com/acdlite), [@​gnoff](https://github.com/gnoff), [@​jackpope](https://github.com/jackpope), [@​rickhanlonii](https://github.com/rickhanlonii))
- Don’t rethrow errors at the root ([#​28627](https://github.com/facebook/react/pull/28627), [#​28641](https://github.com/facebook/react/pull/28641) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Batch sync discrete, continuous, and default lanes ([#​25700](https://github.com/facebook/react/pull/25700) by [@​tyao1](https://github.com/tyao1))
- Switch `<Context>` to mean `<Context.Provider>` ([#​28226](https://github.com/facebook/react/pull/28226) by [@​gaearon](https://github.com/gaearon))
- Changes to *StrictMode*
- Handle `info`, `group`, and `groupCollapsed` in *StrictMode* logging ([#​25172](https://github.com/facebook/react/pull/25172) by [@​timneutkens](https://github.com/timneutkens))
- Refs are now attached/detached/attached in *StrictMode* ([#​25049](https://github.com/facebook/react/pull/25049) by [@​sammy-SC](https://github.com/sammy-SC))
- Fix `useSyncExternalStore()` hydration in *StrictMode* ([#​26791](https://github.com/facebook/react/pull/26791) by [@​sophiebits](https://github.com/sophiebits))
- Always trigger `componentWillUnmount()` in *StrictMode* ([#​26842](https://github.com/facebook/react/pull/26842) by [@​tyao1](https://github.com/tyao1))
- Restore double invoking `useState()` and `useReducer()` initializer functions in *StrictMode* ([#​28248](https://github.com/facebook/react/pull/28248) by [@​eps1lon](https://github.com/eps1lon))
- Reuse memoized result from first pass ([#​25583](https://github.com/facebook/react/pull/25583) by [@​acdlite](https://github.com/acdlite))
- Fix `useId()` in *StrictMode* ([#​25713](https://github.com/facebook/react/pull/25713) by [@​gnoff](https://github.com/gnoff))
- Add component name to *StrictMode* error messages ([#​25718](https://github.com/facebook/react/pull/25718) by [@​sammy-SC](https://github.com/sammy-SC))
- Add support for rendering BigInt ([#​24580](https://github.com/facebook/react/pull/24580) by [@​eps1lon](https://github.com/eps1lon))
- `act()` no longer checks `shouldYield` which can be inaccurate in test environments ([#​26317](https://github.com/facebook/react/pull/26317) by [@​acdlite](https://github.com/acdlite))
- Warn when keys are spread with props ([#​25697](https://github.com/facebook/react/pull/25697), [#​26080](https://github.com/facebook/react/pull/26080) by [@​sebmarkbage](https://github.com/sebmarkbage) and [@​kassens](https://github.com/kassens))
- Generate sourcemaps for production build artifacts ([#​26446](https://github.com/facebook/react/pull/26446) by [@​markerikson](https://github.com/markerikson))
- Improve stack diffing algorithm ([#​27132](https://github.com/facebook/react/pull/27132) by [@​KarimP](https://github.com/KarimP))
- Suspense throttling lowered from 500ms to 300ms ([#​26803](https://github.com/facebook/react/pull/26803) by [@​acdlite](https://github.com/acdlite))
- Lazily propagate context changes ([#​20890](https://github.com/facebook/react/pull/20890) by [@​acdlite](https://github.com/acdlite) and [@​gnoff](https://github.com/gnoff))
- Immediately rerender pinged fiber ([#​25074](https://github.com/facebook/react/pull/25074) by [@​acdlite](https://github.com/acdlite))
- Move update scheduling to microtask ([#​26512](https://github.com/facebook/react/pull/26512) by [@​acdlite](https://github.com/acdlite))
- Consistently apply throttled retries ([#​26611](https://github.com/facebook/react/pull/26611), [#​26802](https://github.com/facebook/react/pull/26802) by [@​acdlite](https://github.com/acdlite))
- Suspend Thenable/Lazy if it's used in React.Children ([#​28284](https://github.com/facebook/react/pull/28284) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Detect infinite update loops caused by render phase updates ([#​26625](https://github.com/facebook/react/pull/26625) by [@​acdlite](https://github.com/acdlite))
- Update conditional hooks warning ([#​29626](https://github.com/facebook/react/pull/29626) by [@​sophiebits](https://github.com/sophiebits))
- Update error URLs to go to new docs ([#​27240](https://github.com/facebook/react/pull/27240) by [@​rickhanlonii](https://github.com/rickhanlonii))
- Rename the `react.element` symbol to `react.transitional.element` ([#​28813](https://github.com/facebook/react/pull/28813) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Fix crash when suspending in shell during `useSyncExternalStore()` re-render ([#​27199](https://github.com/facebook/react/pull/27199) by [@​acdlite](https://github.com/acdlite))
- Fix incorrect “detected multiple renderers" error in tests ([#​22797](https://github.com/facebook/react/pull/22797) by [@​eps1lon](https://github.com/eps1lon))
- Fix bug where effect cleanup may be called twice after bailout ([#​26561](https://github.com/facebook/react/pull/26561) by [@​acdlite](https://github.com/acdlite))
- Fix suspending in shell during discrete update ([#​25495](https://github.com/facebook/react/pull/25495) by [@​acdlite](https://github.com/acdlite))
- Fix memory leak after repeated setState bailouts ([#​25309](https://github.com/facebook/react/pull/25309) by [@​acdlite](https://github.com/acdlite))
- Fix `useSyncExternalStore()` dropped update when state is dispatched in render phase ([#​25578](https://github.com/facebook/react/pull/25578) by [@​pandaiolo](https://github.com/pandaiolo))
- Fix logging when rendering a lazy fragment ([#​30372](https://github.com/facebook/react/pull/30372) by [@​tom-sherman](https://github.com/tom-sherman))
- Remove string refs ([#​25383](https://github.com/facebook/react/pull/25383), [#​28322](https://github.com/facebook/react/pull/28322) by [@​eps1lon](https://github.com/eps1lon) and [@​acdlite](https://github.com/acdlite))
- Remove Legacy Context ([#​30319](https://github.com/facebook/react/issues/30319) by [@​kassens](https://github.com/kassens))
- Remove `RefreshRuntime.findAffectedHostInstances` ([#​30538](https://github.com/facebook/react/pull/30538) by [@​gaearon](https://github.com/gaearon))
- Remove client caching from `cache()` API ([#​27977](https://github.com/facebook/react/pull/27977), [#​28250](https://github.com/facebook/react/pull/28250) by [@​acdlite](https://github.com/acdlite) and [@​gnoff](https://github.com/gnoff))
- Remove `propTypes` ([#​28324](https://github.com/facebook/react/pull/28324), [#​28326](https://github.com/facebook/react/pull/28326) by [@​gaearon](https://github.com/gaearon))
- Remove `defaultProps` support, except for classes ([#​28733](https://github.com/facebook/react/pull/28733) by [@​acdlite](https://github.com/acdlite))
- Remove UMD builds ([#​28735](https://github.com/facebook/react/pull/28735) by [@​gnoff](https://github.com/gnoff))
- Remove delay for non-transition updates ([#​26597](https://github.com/facebook/react/pull/26597) by [@​acdlite](https://github.com/acdlite))
- Remove `createFactory` ([#​27798](https://github.com/facebook/react/pull/27798) by [@​kassens](https://github.com/kassens))
##### React DOM
- Adds Form Actions to handle form submission ([#​26379](https://github.com/facebook/react/pull/26379), [#​26674](https://github.com/facebook/react/pull/26674), [#​26689](https://github.com/facebook/react/pull/26689), [#​26708](https://github.com/facebook/react/pull/26708), [#​26714](https://github.com/facebook/react/pull/26714), [#​26735](https://github.com/facebook/react/pull/26735), [#​26846](https://github.com/facebook/react/pull/26846), [#​27358](https://github.com/facebook/react/pull/27358), [#​28056](https://github.com/facebook/react/pull/28056) by [@​sebmarkbage](https://github.com/sebmarkbage), [@​acdlite](https://github.com/acdlite), and [@​jupapios](https://github.com/jupapios))
- Add `useFormStatus()` hook to provide status information of the last form submission ([#​26719](https://github.com/facebook/react/pull/26719), [#​26722](https://github.com/facebook/react/pull/26722), [#​26788](https://github.com/facebook/react/pull/26788), [#​29019](https://github.com/facebook/react/pull/29019), [#​28728](https://github.com/facebook/react/pull/28728), [#​28413](https://github.com/facebook/react/pull/28413) by [@​acdlite](https://github.com/acdlite) and [@​eps1lon](https://github.com/eps1lon))
- Support for Document Metadata. Adds `preinit`, `preinitModule`, `preconnect`, `prefetchDNS`, `preload`, and `preloadModule` APIs.
- [#​25060](https://github.com/facebook/react/pull/25060), [#​25243](https://github.com/facebook/react/pull/25243), [#​25388](https://github.com/facebook/react/pull/25388), [#​25432](https://github.com/facebook/react/pull/25432), [#​25436](https://github.com/facebook/react/pull/25436), [#​25426](https://github.com/facebook/react/pull/25426), [#​25500](https://github.com/facebook/react/pull/25500), [#​25480](https://github.com/facebook/react/pull/25480), [#​25508](https://github.com/facebook/react/pull/25508), [#​25515](https://github.com/facebook/react/pull/25515), [#​25514](https://github.com/facebook/react/pull/25514), [#​25532](https://github.com/facebook/react/pull/25532), [#​25536](https://github.com/facebook/react/pull/25536), [#​25534](https://github.com/facebook/react/pull/25534), [#​25546](https://github.com/facebook/react/pull/25546), [#​25559](https://github.com/facebook/react/pull/25559), [#​25569](https://github.com/facebook/react/pull/25569), [#​25599](https://github.com/facebook/react/pull/25599), [#​25689](https://github.com/facebook/react/pull/25689), [#​26106](https://github.com/facebook/react/pull/26106), [#​26152](https://github.com/facebook/react/pull/26152), [#​26239](https://github.com/facebook/react/pull/26239), [#​26237](https://github.com/facebook/react/pull/26237), [#​26280](https://github.com/facebook/react/pull/26280), [#​26154](https://github.com/facebook/react/pull/26154), [#​26256](https://github.com/facebook/react/pull/26256), [#​26353](https://github.com/facebook/react/pull/26353), [#​26427](https://github.com/facebook/react/pull/26427), [#​26450](https://github.com/facebook/react/pull/26450), [#​26502](https://github.com/facebook/react/pull/26502), [#​26514](https://github.com/facebook/react/pull/26514), [#​26531](https://github.com/facebook/react/pull/26531), [#​26532](https://github.com/facebook/react/pull/26532), [#​26557](https://github.com/facebook/react/pull/26557), [#​26871](https://github.com/facebook/react/pull/26871), [#​26881](https://github.com/facebook/react/pull/26881), [#​26877](https://github.com/facebook/react/pull/26877), [#​26873](https://github.com/facebook/react/pull/26873), [#​26880](https://github.com/facebook/react/pull/26880), [#​26942](https://github.com/facebook/react/pull/26942), [#​26938](https://github.com/facebook/react/pull/26938), [#​26940](https://github.com/facebook/react/pull/26940), [#​26939](https://github.com/facebook/react/pull/26939), [#​27030](https://github.com/facebook/react/pull/27030), [#​27201](https://github.com/facebook/react/pull/27201), [#​27212](https://github.com/facebook/react/pull/27212), [#​27217](https://github.com/facebook/react/pull/27217), [#​27218](https://github.com/facebook/react/pull/27218), [#​27220](https://github.com/facebook/react/pull/27220), [#​27224](https://github.com/facebook/react/pull/27224), [#​27223](https://github.com/facebook/react/pull/27223), [#​27269](https://github.com/facebook/react/pull/27269), [#​27260](https://github.com/facebook/react/pull/27260), [#​27347](https://github.com/facebook/react/pull/27347), [#​27346](https://github.com/facebook/react/pull/27346), [#​27361](https://github.com/facebook/react/pull/27361), [#​27400](https://github.com/facebook/react/pull/27400), [#​27541](https://github.com/facebook/react/pull/27541), [#​27610](https://github.com/facebook/react/pull/27610), [#​28110](https://github.com/facebook/react/pull/28110), [#​29693](https://github.com/facebook/react/pull/29693), [#​29732](https://github.com/facebook/react/pull/29732), [#​29811](https://github.com/facebook/react/pull/29811), [#​27586](https://github.com/facebook/react/pull/27586), [#​28069](https://github.com/facebook/react/pull/28069) by [@​gnoff](https://github.com/gnoff), [@​sebmarkbage](https://github.com/sebmarkbage), [@​acdlite](https://github.com/acdlite), [@​kassens](https://github.com/kassens), [@​sokra](https://github.com/sokra), [@​sweetliquid](https://github.com/sweetliquid)
- Add `fetchPriority` to `<img>` and `<link>` ([#​25927](https://github.com/facebook/react/pull/25927) by [@​styfle](https://github.com/styfle))
- Add support for SVG `transformOrigin` prop ([#​26130](https://github.com/facebook/react/pull/26130) by [@​arav-ind](https://github.com/arav-ind))
- Add support for `onScrollEnd` event ([#​26789](https://github.com/facebook/react/pull/26789) by [@​devongovett](https://github.com/devongovett))
- Allow `<hr>` as child of `<select>` ([#​27632](https://github.com/facebook/react/pull/27632) by [@​SouSingh](https://github.com/SouSingh))
- Add support for Popover API ([#​27981](https://github.com/facebook/react/pull/27981) by [@​eps1lon](https://github.com/eps1lon))
- Add support for `inert` ([#​24730](https://github.com/facebook/react/pull/24730) by [@​eps1lon](https://github.com/eps1lon))
- Add support for `imageSizes` and `imageSrcSet` ([#​22550](https://github.com/facebook/react/pull/22550) by [@​eps1lon](https://github.com/eps1lon))
- Synchronously flush transitions in popstate events ([#​26025](https://github.com/facebook/react/pull/26025), [#​27559](https://github.com/facebook/react/pull/27559), [#​27505](https://github.com/facebook/react/pull/27505), [#​30759](https://github.com/facebook/react/pull/30759) by [@​tyao1](https://github.com/tyao1) and [@​acdlite](https://github.com/acdlite))
- `flushSync` exhausts queue even if something throws ([#​26366](https://github.com/facebook/react/pull/26366) by [@​acdlite](https://github.com/acdlite))
- Throw error if `react` and `react-dom` versions don’t match ([#​29236](https://github.com/facebook/react/pull/29236) by [@​acdlite](https://github.com/acdlite))
- Ensure `srcset` and `src` are assigned last on `<img>` instances ([#​30340](https://github.com/facebook/react/pull/30340) by [@​gnoff](https://github.com/gnoff))
- Javascript URLs are replaced with functions that throw errors ([#​26507](https://github.com/facebook/react/pull/26507), [#​29808](https://github.com/facebook/react/pull/29808) by [@​sebmarkbage](https://github.com/sebmarkbage) and [@​kassens](https://github.com/kassens))
- Treat toggle and beforetoggle as discrete events ([#​29176](https://github.com/facebook/react/pull/29176) by [@​eps1lon](https://github.com/eps1lon))
- Filter out empty `src` and `href` attributes (unless for `<a href=”” />`) ([#​18513](https://github.com/facebook/react/pull/18513), [#​28124](https://github.com/facebook/react/pull/28124) by [@​bvaughn](https://github.com/bvaughn) and [@​eps1lon](https://github.com/eps1lon))
- Fix unitless `scale` style property ([#​25601](https://github.com/facebook/react/pull/25601) by [@​JonnyBurger](https://github.com/JonnyBurger))
- Fix `onChange` error message for controlled `<select>` ([#​27740](https://github.com/facebook/react/pull/27740) by [@​Biki-das](https://github.com/Biki-das))
- Fix focus restore in child windows after element reorder ([#​30951](https://github.com/facebook/react/pull/30951) by [@​ling1726](https://github.com/ling1726))
- Remove `render`, `hydrate`, `findDOMNode`, `unmountComponentAtNode`, `unstable_createEventHandle`, `unstable_renderSubtreeIntoContainer`, and `unstable_runWithPriority`. Move `createRoot` and `hydrateRoot` to `react-dom/client`. ([#​28271](https://github.com/facebook/react/pull/28271) by [@​gnoff](https://github.com/gnoff))
- Remove `test-utils` ([#​28541](https://github.com/facebook/react/pull/28541) by [@​eps1lon](https://github.com/eps1lon))
- Remove `unstable_flushControlled` ([#​26397](https://github.com/facebook/react/pull/26397) by [@​kassens](https://github.com/kassens))
- Remove legacy mode ([#​28468](https://github.com/facebook/react/pull/28468) by [@​gnoff](https://github.com/gnoff))
- Remove `renderToStaticNodeStream()` ([#​28873](https://github.com/facebook/react/pull/28873) by [@​gnoff](https://github.com/gnoff))
- Remove `unstable_renderSubtreeIntoContainer` ([#​29771](https://github.com/facebook/react/pull/29771) by [@​kassens](https://github.com/kassens))
##### React DOM Server
- Stable release of React Server Components ([Many, many PRs](https://github.com/facebook/react/pulls?q=is%3Apr+is%3Aclosed+%5BFlight%5D+in%3Atitle+created%3A%3C2024-12-01+) by [@​sebmarkbage](https://github.com/sebmarkbage), [@​acdlite](https://github.com/acdlite), [@​gnoff](https://github.com/gnoff), [@​sammy-SC](https://github.com/sammy-SC), [@​gaearon](https://github.com/gaearon), [@​sophiebits](https://github.com/sophiebits), [@​unstubbable](https://github.com/unstubbable), [@​lubieowoce](https://github.com/lubieowoce))
- Support Server Actions ([#​26124](https://github.com/facebook/react/pull/26124), [#​26632](https://github.com/facebook/react/pull/26632), [#​27459](https://github.com/facebook/react/pull/27459) by [@​sebmarkbage](https://github.com/sebmarkbage) and [@​acdlite](https://github.com/acdlite))
- Changes to SSR
- Add external runtime which bootstraps hydration on the client for binary transparency ([#​25437](https://github.com/facebook/react/pull/25437), [#​26169](https://github.com/facebook/react/pull/26169), [#​25499](https://github.com/facebook/react/pull/25499) by [@​MofeiZ](https://github.com/mofeiZ) and [@​acdlite](https://github.com/acdlite))
- Support subresource integrity for `bootstrapScripts` and `bootstrapModules` ([#​25104](https://github.com/facebook/react/pull/25104) by [@​gnoff](https://github.com/gnoff))
- Fix null bytes written at text chunk boundaries ([#​26228](https://github.com/facebook/react/pull/26228) by [@​sophiebits](https://github.com/sophiebits))
- Fix logic around attribute serialization ([#​26526](https://github.com/facebook/react/pull/26526) by [@​gnoff](https://github.com/gnoff))
- Fix precomputed chunk cleared on Node 18 ([#​25645](https://github.com/facebook/react/pull/25645) by [@​feedthejim](https://github.com/feedthejim))
- Optimize end tag chunks ([#​27522](https://github.com/facebook/react/pull/27522) by [@​yujunjung](https://github.com/yujunjung))
- Gracefully handle suspending in DOM configs ([#​26768](https://github.com/facebook/react/pull/26768) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Check for nullish values on ReactCustomFormAction ([#​26770](https://github.com/facebook/react/pull/26770) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Preload `bootstrapModules`, `bootstrapScripts`, and update priority queue ([#​26754](https://github.com/facebook/react/pull/26754), [#​26753](https://github.com/facebook/react/pull/26753), [#​27190](https://github.com/facebook/react/pull/27190), [#​27189](https://github.com/facebook/react/pull/27189) by [@​gnoff](https://github.com/gnoff))
- Client render the nearest child or parent suspense boundary if replay errors or is aborted ([#​27386](https://github.com/facebook/react/pull/27386) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Don't bail out of flushing if we still have pending root tasks ([#​27385](https://github.com/facebook/react/pull/27385) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Ensure Resumable State is Serializable ([#​27388](https://github.com/facebook/react/pull/27388) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Remove extra render pass when reverting to client render ([#​26445](https://github.com/facebook/react/pull/26445) by [@​acdlite](https://github.com/acdlite))
- Fix unwinding context during selective hydration ([#​25876](https://github.com/facebook/react/pull/25876) by [@​tyao1](https://github.com/tyao1))
- Stop flowing and then abort if a stream is cancelled ([#​27405](https://github.com/facebook/react/pull/27405) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Pass cancellation reason to abort ([#​27536](https://github.com/facebook/react/pull/27536) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Add `onHeaders` entrypoint option ([#​27641](https://github.com/facebook/react/pull/27641), [#​27712](https://github.com/facebook/react/pull/27712) by [@​gnoff](https://github.com/gnoff))
- Escape `<style>` and `<script>` textContent to enable rendering inner content without dangerouslySetInnerHTML ([#​28870](https://github.com/facebook/react/pull/28870), [#​28871](https://github.com/facebook/react/pull/28871) by [@​gnoff](https://github.com/gnoff))
- Fallback to client replaying actions for Blob serialization ([#​28987](https://github.com/facebook/react/pull/28987) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Render Suspense fallback if boundary contains new stylesheet during sync update ([#​28965](https://github.com/facebook/react/pull/28965) by [@​gnoff](https://github.com/gnoff))
- Fix header length tracking ([#​30327](https://github.com/facebook/react/issues/30327) by [@​gnoff](https://github.com/gnoff))
- Use `srcset` to trigger load event on mount ([#​30351](https://github.com/facebook/react/issues/30351) by [@​gnoff](https://github.com/gnoff))
- Don't perform work when closing stream ([#​30497](https://github.com/facebook/react/issues/30497) by [@​gnoff](https://github.com/gnoff))
- Allow aborting during render ([#​30488](https://github.com/facebook/react/issues/30488), [#​30730](https://github.com/facebook/react/pull/30730) by [@​gnoff](https://github.com/gnoff))
- Start initial work immediately ([#​31079](https://github.com/facebook/react/issues/31079) by [@​gnoff](https://github.com/gnoff))
- A transition flowing into a dehydrated boundary no longer suspends when showing fallback ([#​27230](https://github.com/facebook/react/pull/27230) by [@​acdlite](https://github.com/acdlite))
- Fix selective hydration triggers false update loop error ([#​27439](https://github.com/facebook/react/pull/27439) by [@​acdlite](https://github.com/acdlite))
- Warn for Child Iterator of all types but allow Generator Components ([#​28853](https://github.com/facebook/react/pull/28853) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Include regular stack trace in serialized errors ([#​28684](https://github.com/facebook/react/pull/28684), [#​28738](https://github.com/facebook/react/pull/28738) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Aborting early no longer infinitely suspends ([#​24751](https://github.com/facebook/react/pull/24751) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Fix hydration warning suppression in text comparisons ([#​24784](https://github.com/facebook/react/pull/24784) by [@​gnoff](https://github.com/gnoff))
- Changes to error handling in SSR
- Add diffs to hydration warnings ([#​28502](https://github.com/facebook/react/pull/28502), [#​28512](https://github.com/facebook/react/pull/28512) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Make Error creation lazy ([#​24728](https://github.com/facebook/react/pull/24728) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Remove recoverable error when a sync update flows into a dehydrated boundary ([#​25692](https://github.com/facebook/react/pull/25692) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Don't "fix up" mismatched text content with suppressedHydrationWarning ([#​26391](https://github.com/facebook/react/pull/26391) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Fix component stacks in errors ([#​27456](https://github.com/facebook/react/pull/27456) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Add component stacks to `onError` ([#​27761](https://github.com/facebook/react/pull/27761), [#​27850](https://github.com/facebook/react/pull/27850) by [@​gnoff](https://github.com/gnoff) and [@​sebmarkbage](https://github.com/sebmarkbage))
- Throw hydration mismatch errors once ([#​28502](https://github.com/facebook/react/pull/28502) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Add Bun streaming server renderer ([#​25597](https://github.com/facebook/react/pull/25597) by [@​colinhacks](https://github.com/colinhacks))
- Add nonce support to bootstrap scripts ([#​26738](https://github.com/facebook/react/pull/26738) by [@​danieltott](https://github.com/danieltott))
- Add `crossorigin` support to bootstrap scripts ([#​26844](https://github.com/facebook/react/pull/26844) by [@​HenriqueLimas](https://github.com/HenriqueLimas))
- Support `nonce` and `fetchpriority` in preload links ([#​26826](https://github.com/facebook/react/pull/26826) by [@​liuyenwei](https://github.com/liuyenwei))
- Add `referrerPolicy` to `ReactDOM.preload()` ([#​27096](https://github.com/facebook/react/pull/27096) by [@​styfle](https://github.com/styfle))
- Add server condition for `react/jsx-dev-runtime` ([#​28921](https://github.com/facebook/react/pull/28921) by [@​himself65](https://github.com/himself65))
- Export version ([#​29596](https://github.com/facebook/react/pull/29596) by [@​unstubbable](https://github.com/unstubbable))
- Rename the secret export of Client and Server internals ([#​28786](https://github.com/facebook/react/pull/28786), [#​28789](https://github.com/facebook/react/pull/28789) by [@​sebmarkbage](https://github.com/sebmarkbage))
- Remove layout effect warning on server ([#​26395](https://github.com/facebook/react/pull/26395) by [@​rickhanlonii](https://github.com/rickhanlonii))
- Remove `errorInfo.digest` from `onRecoverableError` ([#​28222](https://github.com/facebook/react/pull/28222) by [@​gnoff](https://github.com/gnoff))
##### ReactTestRenderer
- Add deprecation error to `react-test-renderer` on web ([#​27903](https://github.com/facebook/react/pull/27903), [#​28904](https://github.com/facebook/react/pull/28904) by [@​jackpope](https://github.com/jackpope) and [@​acdlite](https://github.com/acdlite))
- Render with ConcurrentRoot on web ([#​28498](https://github.com/facebook/react/pull/28498) by [@​jackpope](https://github.com/jackpope))
- Remove `react-test-renderer/shallow` export ([#​25475](https://github.com/facebook/react/pull/25475), [#​28497](https://github.com/facebook/react/pull/28497) by [@​sebmarkbage](https://github.com/sebmarkbage) and [@​jackpope](https://github.com/jackpope))
##### React Reconciler
- Enable suspending commits without blocking render ([#​26398](https://github.com/facebook/react/pull/26398), [#​26427](https://github.com/facebook/react/pull/26427) by [@​acdlite](https://github.com/acdlite))
- Remove `prepareUpdate` ([#​26583](https://github.com/facebook/react/pull/26583), [#​27409](http://github.com/facebook/react/pull/27409) by [@​sebmarkbage](https://github.com/sebmarkbage) and [@​sophiebits](https://github.com/sophiebits))
##### React-Is
- Enable tree shaking ([#​27701](https://github.com/facebook/react/pull/27701) by [@​markerikson](https://github.com/markerikson))
- Remove `isConcurrentMode` and `isAsyncMode` methods ([#​28224](https://github.com/facebook/react/pull/28224) by [@​gaearon](https://github.com/gaearon))
##### useSyncExternalStore
- Remove React internals access ([#​29868](https://github.com/facebook/react/pull/29868) by [@​phryneas](https://github.com/phryneas))
- Fix stale selectors keeping previous store references ([#​25969](https://github.com/facebook/react/pull/25968) by [@​jellevoost](https://github.com/jellevoost))
</details>
---
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A planned feature of useFormState is that if the page load is the result of an MPA-style form submission — i.e. a form was submitted before it was hydrated, using Server Actions — the state of the hook should transfer to the next page.
I haven't implemented that part yet, but as a prerequisite, we need some way for Fizz to indicate whether a useFormState hook was rendered using the "postback" state. That way we can do all state matching logic on the server without having to replicate it on the client, too.
The approach here is to emit a comment node for each useFormState hook. We use one of two comment types:
<!--F-->for a normal useFormState hook, and<!--F!-->for a hook that was rendered using the postback state. React will read these markers during hydration. This is similar to how we encode Suspense boundaries.Again, the actual matching algorithm is not yet implemented — for now, the "not matching" marker is always emitted.
We can optimize this further by not emitting any markers for a render that is not the result of a form postback, which I'll do in subsequent PRs.