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experimental_use(promise) #25084
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}, | ||
); | ||
} | ||
throw thenable; |
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Should we add ping listeners directly here and instead throw a placeholder value?
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Yeah I can do that
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if (suspendedThenables === null) { | ||
suspendedThenables = []; | ||
} | ||
suspendedThenables[index] = thenable; |
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So this is a holey array which is pretty deopted. I wonder if it might be worth just setting it to null for every use()
call even if nothing suspends. Perhaps reusing the same array every time and filling it with null each time. Maybe that's worse.
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Maybe @gsathya would know which is best
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Looks like this got replaced by expandos? Expandos will cause hidden class transition leading to a potential deopt. Curious if WeakMap works for you? Or is too slow?
I guess, the tradeoff here is between slow lookup in WeakMaps or a deopt in other parts that use this thenable -- I don't know which is the more common workload.
As an aside, if looking up the Promise value synchronously is the common case, then we could champion a Promise.prototype.inspect
proposal to add this to the Promise API.
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Promise.prototype.inspect
wouldn't help in this particular case because this array is for tracking thenables that aren't cached. We use it when we know two thenables represent the same data even though they are different objects. For example:
const helloPromise = Promise.resolve('Hello');
function HelloWorld() {
// This component uses different promises on every render attempt,
// but if no React state has changed we know that the underlying value
// can be reused.
return
// This promise is the same every time, so we can read the value
// from the expando (a la Promise.prototype.inspect)
use(helloPromise) +
// This promise is new every time, but we know it represents the
// same thing, so we reuse the previous value from the array.
use(Promise.resolve('World');
}
In the current implementation, this example would produce a sparse array with a value at index 1 and a hole at index 0.
The reason index 0 is a hole is because if the promise can be inspected, there's no reason to track it. So Seb's suggestion is that it might be better to push to the array even if it's not needed.
There are other solutions to avoid a holey array, like only advancing the thenableIndex if the promise hasn't resolved. I think that would require one additional null check to each read of an inspectable promise, but it might be worth it to prevent a deopt.
default: { | ||
// The thenable still hasn't resolved. Suspend with the same | ||
// thenable as last time to avoid redundant listeners. | ||
throw prevThenableAtIndex; |
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This seems like it should be an error case - e.g. you used something mutable conditionally.
We shouldn't bother retrying immediately unless lastUsedThenable
was pinged. There's no point in retrying due to anything else because that can no longer be blocking. Anything preceding lastUsedThenable must have already been resolved or we wouldn't have gotten that far.
If something else pings maybe we need to reset the suspended thenables anyway - e.g. if we want to treat it as a restart.
So if we have anything in the slot from before, it must've been resolved. Otherwise something went wrong.
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Yeah that seems reasonable. I started a list of a warning cases but maybe this one should be an actual error
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We shouldn't bother retrying immediately unless lastUsedThenable was pinged. There's no point in retrying due to anything else because that can no longer be blocking. Anything preceding lastUsedThenable must have already been resolved or we wouldn't have gotten that far.
Yeah that is how it currently works. It's a different variable though because it also works for ad hoc wakeables (ones that aren't use
-d), but the same logic you're describing:
react/packages/react-reconciler/src/ReactFiberWakeable.new.js
Lines 28 to 34 in 796d318
if (wakeable === suspendedWakeable) { | |
// This ping is from the wakeable that just suspended. Mark it as pinged. | |
// When the work loop resumes, we'll immediately try rendering the fiber | |
// again instead of unwinding the stack. | |
wasPinged = true; | |
return true; | |
} |
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This update our internal implementation of `act` to support React's new behavior for unwrapping promises. Like we did with Scheduler, when something suspends, it will yield to the main thread so the microtasks can run, then continue in a new task. I need to implement the same behavior in the public version of `act`, but there are some additional considerations so I'll do that in a separate commit.
throwException is the function that finds the nearest boundary and schedules it for a second render pass. We should only call it right before we unwind the stack — not if we receive an immediate ping and render the fiber again. This was an oversight in 8ef3a7c that I didn't notice because it happens to mostly work, anyway. What made me notice the mistake is that throwException also marks the entire render phase as suspended (RootDidSuspend or RootDidSuspendWithDelay), which is only supposed to be happen if we show a fallback. One consequence was that, in the RootDidSuspendWithDelay case, the entire commit phase was blocked, because that's the exit status we use to block a bad fallback from appearing.
Add a `status` expando to a thrown thenable to track when its value has resolved. In a later step, we'll also use `value` and `reason` expandos to track the resolved value. This is not part of the official JavaScript spec — think of it as an extension of the Promise API, or a custom interface that is a superset of Thenable. However, it's inspired by the terminology used by `Promise.allSettled`. The intent is that this will be a public API — Suspense implementations can set these expandos to allow React to unwrap the value synchronously without waiting a microtask.
Sets up a new experimental hook behind a feature flag, but does not implement it yet.
@nl0 this API is experimental and still in research so there's no target for release yet. |
* 'main' of ssh://github.com/GrinZero/react: (26 commits) [devtools][easy] Fix flow type (facebook#25147) Remove Symbol Polyfill (again) (facebook#25144) Remove ReactFiberFlags MountLayoutDev and MountPassiveDev (facebook#25091) experimental_use(promise) (facebook#25084) [Transition Tracing] onMarkerIncomplete - Tracing Marker/Suspense Boundary Deletions (facebook#24885) [Flight] Add support for Webpack Async Modules (facebook#25138) Fix typo: supportsMicrotask -> supportsMicrotasks (facebook#25142) Allow functions to be used as module references (facebook#25137) Test the node-register hooks in unit tests (facebook#25132) Return closestInstance in `getInspectorDataForViewAtPoint` (facebook#25118) [DevTools] Highlight RN elements on hover (facebook#25106) Update fixtures/flight to webpack 5 (facebook#25115) Align StrictMode behaviour with production (facebook#25049) Scaffolding for useMemoCache hook (facebook#25123) devtools: Fix typo from directores to directories (facebook#25124) fixture: Fix typo from perfomrance to performance (facebook#25100) [DevTools] Add events necessary for click to inspect on RN (facebook#25111) Add missing createServerContext for experimental shared subset (facebook#25114) support subresource integrity for bootstrapScripts and bootstrapModules (facebook#25104) make preamble and postamble types explicit and fix typo (facebook#25102) ...
Follow up to facebook#25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
Follow up to facebook#25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
Follow up to facebook#25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
Follow up to facebook#25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
Follow up to #25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
Follow up to facebook#25084. Implements experimental_use(promise) API in the SSR runtime (Fizz). This is largely a copy-paste of the Flight implementation. I have intentionally tried to keep both as close as possible.
Follow up to facebook#25084 and facebook#25207. Implements experimental_use(promise) API in the SSR runtime (Fizz). This is largely a copy-paste of the Flight implementation. I have intentionally tried to keep both as close as possible.
Follow up to facebook#25084 and facebook#25207. Implements experimental_use(promise) API in the SSR runtime (Fizz). This is largely a copy-paste of the Flight implementation. I have intentionally tried to keep both as close as possible.
- [`experimental` entrypoint](https://unpkg.com/browse/[email protected]/cjs/react.development.js) - [implementation in `experimental`](https://unpkg.com/browse/[email protected]/cjs/react-dom.development.js) - [experimental_use(Thenable)](facebook/react#25084) - [experimental_use(Context)](facebook/react#25202)
- [`experimental` entrypoint](https://unpkg.com/browse/[email protected]/cjs/react.development.js) - [implementation in `experimental`](https://unpkg.com/browse/[email protected]/cjs/react-dom.development.js) - [experimental_use(Thenable)](facebook/react#25084) - [experimental_use(Context)](facebook/react#25202)
- [`experimental` entrypoint](https://unpkg.com/browse/[email protected]/cjs/react.development.js) - [implementation in `experimental`](https://unpkg.com/browse/[email protected]/cjs/react-dom.development.js) - [experimental_use(Thenable)](facebook/react#25084) - [experimental_use(Context)](facebook/react#25202)
Follow up to #25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
Summary: This sync includes the following changes: - **[c28f313e6](facebook/react@c28f313e6 )**: experimental_use(promise) for SSR ([#25214](facebook/react#25214)) //<Andrew Clark>// - **[d6f9628a8](facebook/react@d6f9628a8 )**: Remove some RSC subset entry points that were removed in the main entry point ([#25209](facebook/react#25209)) //<Sebastian Markbåge>// - **[a473d08fc](facebook/react@a473d08fc )**: Update to Flow from 0.97 to 0.122 ([#25204](facebook/react#25204)) //<Jan Kassens>// - **[7028ce745](facebook/react@7028ce745 )**: experimental_use(promise) for Server Components ([#25207](facebook/react#25207)) //<Andrew Clark>// - **[bfb65681e](facebook/react@bfb65681e )**: experimental_use(context)([#25202](facebook/react#25202)) //<mofeiZ>// - **[f0efa1164](facebook/react@f0efa1164 )**: [flow] remove custom suppress comment config ([#25170](facebook/react#25170)) //<Jan Kassens>// - **[2e7f422fe](facebook/react@2e7f422fe )**: Refactor: its type is Container ([#25153](facebook/react#25153)) //<bubucuo>// - **[2c2d9a1df](facebook/react@2c2d9a1df )**: [eslint-plugin-react-hooks] only allow capitalized component names ([#25162](facebook/react#25162)) //<Jan Kassens>// - **[36c908a6c](facebook/react@36c908a6c )**: Don't use the Flight terminology in public error messages ([#25166](facebook/react#25166)) //<Sebastian Markbåge>// - **[8d1b057ec](facebook/react@8d1b057ec )**: [Flight] Minor error handling fixes ([#25151](facebook/react#25151)) //<Sebastian Markbåge>// - **[9ff738f53](facebook/react@9ff738f53 )**: [devtools][easy] Fix flow type ([#25147](facebook/react#25147)) //<Tianyu Yao>// - **[0de3ddf56](facebook/react@0de3ddf56 )**: Remove Symbol Polyfill (again) ([#25144](facebook/react#25144)) //<Ricky>// - **[b36f72235](facebook/react@b36f72235 )**: Remove ReactFiberFlags MountLayoutDev and MountPassiveDev ([#25091](facebook/react#25091)) //<Samuel Susla>// - **[b6978bc38](facebook/react@b6978bc38 )**: experimental_use(promise) ([#25084](facebook/react#25084)) //<Andrew Clark>// - **[11ed7010c](facebook/react@11ed7010c )**: [Transition Tracing] onMarkerIncomplete - Tracing Marker/Suspense Boundary Deletions ([#24885](facebook/react#24885)) //<Luna Ruan>// - **[b79894259](facebook/react@b79894259 )**: [Flight] Add support for Webpack Async Modules ([#25138](facebook/react#25138)) //<Sebastian Markbåge>// - **[c8b778b7f](facebook/react@c8b778b7f )**: Fix typo: supportsMicrotask -> supportsMicrotasks ([#25142](facebook/react#25142)) //<kwzr>// - **[d0f396651](facebook/react@d0f396651 )**: Allow functions to be used as module references ([#25137](facebook/react#25137)) //<Sebastian Markbåge>// - **[38c5d8a03](facebook/react@38c5d8a03 )**: Test the node-register hooks in unit tests ([#25132](facebook/react#25132)) //<Sebastian Markbåge>// - **[3f70e68ce](facebook/react@3f70e68ce )**: Return closestInstance in `getInspectorDataForViewAtPoint` ([#25118](facebook/react#25118)) //<Tianyu Yao>// - **[3d443cad7](facebook/react@3d443cad7 )**: Update fixtures/flight to webpack 5 ([#25115](facebook/react#25115)) //<Tim Neutkens>// - **[5d1ce6513](facebook/react@5d1ce6513 )**: Align StrictMode behaviour with production ([#25049](facebook/react#25049)) //<Samuel Susla>// - **[9e67e7a31](facebook/react@9e67e7a31 )**: Scaffolding for useMemoCache hook ([#25123](facebook/react#25123)) //<Joseph Savona>// - **[19e9a4c68](facebook/react@19e9a4c68 )**: Add missing createServerContext for experimental shared subset ([#25114](facebook/react#25114)) //<Jiachi Liu>// - **[6ef466c68](facebook/react@6ef466c68 )**: make preamble and postamble types explicit and fix typo ([#25102](facebook/react#25102)) //<Josh Story>// - **[796d31809](facebook/react@796d31809 )**: Implement basic stylesheet Resources for react-dom ([#25060](facebook/react#25060)) //<Josh Story>// - **[32baab38f](facebook/react@32baab38f )**: [Transition Tracing] Add Tag Field to Marker Instance ([#25085](facebook/react#25085)) //<Luna Ruan>// - **[8ef3a7c08](facebook/react@8ef3a7c08 )**: Resume immediately pinged fiber without unwinding ([#25074](facebook/react#25074)) //<Andrew Clark>// - **[7bcc68772](facebook/react@7bcc68772 )**: Remove argument committedLanes from reappearLayoutEffects and recursivelyTraverseReappearLayoutEffects ([#25080](facebook/react#25080)) //<Samuel Susla>// - **[ca990e9a7](facebook/react@ca990e9a7 )**: Add API to force Scheduler to yield for macrotask ([#25044](facebook/react#25044)) //<Andrew Clark>// - **[b4204ede6](facebook/react@b4204ede6 )**: Clean up unused Deletion flag ([#24992](facebook/react#24992)) //<Andrew Clark>// - **[e193be87e](facebook/react@e193be87e )**: [Transition Tracing] Add Offscreen Test ([#25035](facebook/react#25035)) //<Luna Ruan>// - **[9fcaf88d5](facebook/react@9fcaf88d5 )**: Remove rootContainerInstance from unnecessary places ([#25024](facebook/react#25024)) //<Sebastian Markbåge>// - **[80f3d8819](facebook/react@80f3d8819 )**: Mount/unmount passive effects when Offscreen visibility changes ([#24977](facebook/react#24977)) //<Andrew Clark>// Changelog: [General][Changed] - React Native sync for revisions 4ea064e...c28f313 Reviewed By: rickhanlonii Differential Revision: D39384898 fbshipit-source-id: 20b080a53851d6dd9d522c8468dd02aab9ba76db
* Internal `act`: Unwrapping resolved promises This update our internal implementation of `act` to support React's new behavior for unwrapping promises. Like we did with Scheduler, when something suspends, it will yield to the main thread so the microtasks can run, then continue in a new task. I need to implement the same behavior in the public version of `act`, but there are some additional considerations so I'll do that in a separate commit. * Move throwException to after work loop resumes throwException is the function that finds the nearest boundary and schedules it for a second render pass. We should only call it right before we unwind the stack — not if we receive an immediate ping and render the fiber again. This was an oversight in 8ef3a7c that I didn't notice because it happens to mostly work, anyway. What made me notice the mistake is that throwException also marks the entire render phase as suspended (RootDidSuspend or RootDidSuspendWithDelay), which is only supposed to be happen if we show a fallback. One consequence was that, in the RootDidSuspendWithDelay case, the entire commit phase was blocked, because that's the exit status we use to block a bad fallback from appearing. * Use expando to check whether promise has resolved Add a `status` expando to a thrown thenable to track when its value has resolved. In a later step, we'll also use `value` and `reason` expandos to track the resolved value. This is not part of the official JavaScript spec — think of it as an extension of the Promise API, or a custom interface that is a superset of Thenable. However, it's inspired by the terminology used by `Promise.allSettled`. The intent is that this will be a public API — Suspense implementations can set these expandos to allow React to unwrap the value synchronously without waiting a microtask. * Scaffolding for `experimental_use` hook Sets up a new experimental hook behind a feature flag, but does not implement it yet. * use(promise) Adds experimental support to Fiber for unwrapping the value of a promise inside a component. It is not yet implemented for Server Components, but that is planned. If promise has already resolved, the value can be unwrapped "immediately" without showing a fallback. The trick we use to implement this is to yield to the main thread (literally suspending the work loop), wait for the microtask queue to drain, then check if the promise resolved in the meantime. If so, we can resume the last attempted fiber without unwinding the stack. This functionality was implemented in previous commits. Another feature is that the promises do not need to be cached between attempts. Because we assume idempotent execution of components, React will track the promises that were used during the previous attempt and reuse the result. You shouldn't rely on this property, but during initial render it mostly just works. Updates are trickier, though, because if you used an uncached promise, we have no way of knowing whether the underlying data has changed, so we have to unwrap the promise every time. It will still work, but it's inefficient and can lead to unnecessary fallbacks if it happens during a discrete update. When we implement this for Server Components, this will be less of an issue because there are no updates in that environment. However, it's still better for performance to cache data requests, so the same principles largely apply. The intention is that this will eventually be the only supported way to suspend on arbitrary promises. Throwing a promise directly will be deprecated.
Follow up to #25084. Implements experimental_use(promise) API in the Server Components runtime (Flight). The implementation is much simpler than in Fiber because there is no state. Even the "state" added in this PR — to track the result of each promise across attempts — is reset as soon as a component successfully renders without suspending. There are also fewer caveats around neglecting to cache a promise because the state of the promises is preserved even if we switch to a different task. Server Components is the primary runtime where this API is intended to be used. The last runtime where we need to implement this is the server renderer (Fizz).
This reverts commit c28f313. Follow up to facebook#25084 and facebook#25207. Implements experimental_use(promise) API in the SSR runtime (Fizz). This is largely a copy-paste of the Flight implementation. I have intentionally tried to keep both as close as possible.
This reverts commit dedfeff. This reverts commit c28f313. Follow up to facebook#25084 and facebook#25207. Implements experimental_use(promise) API in the SSR runtime (Fizz). This is largely a copy-paste of the Flight implementation. I have intentionally tried to keep both as close as possible.
Summary: This sync includes the following changes: - **[c28f313e6](facebook/react@c28f313e6 )**: experimental_use(promise) for SSR ([facebook#25214](facebook/react#25214)) //<Andrew Clark>// - **[d6f9628a8](facebook/react@d6f9628a8 )**: Remove some RSC subset entry points that were removed in the main entry point ([facebook#25209](facebook/react#25209)) //<Sebastian Markbåge>// - **[a473d08fc](facebook/react@a473d08fc )**: Update to Flow from 0.97 to 0.122 ([facebook#25204](facebook/react#25204)) //<Jan Kassens>// - **[7028ce745](facebook/react@7028ce745 )**: experimental_use(promise) for Server Components ([facebook#25207](facebook/react#25207)) //<Andrew Clark>// - **[bfb65681e](facebook/react@bfb65681e )**: experimental_use(context)([facebook#25202](facebook/react#25202)) //<mofeiZ>// - **[f0efa1164](facebook/react@f0efa1164 )**: [flow] remove custom suppress comment config ([facebook#25170](facebook/react#25170)) //<Jan Kassens>// - **[2e7f422fe](facebook/react@2e7f422fe )**: Refactor: its type is Container ([facebook#25153](facebook/react#25153)) //<bubucuo>// - **[2c2d9a1df](facebook/react@2c2d9a1df )**: [eslint-plugin-react-hooks] only allow capitalized component names ([facebook#25162](facebook/react#25162)) //<Jan Kassens>// - **[36c908a6c](facebook/react@36c908a6c )**: Don't use the Flight terminology in public error messages ([facebook#25166](facebook/react#25166)) //<Sebastian Markbåge>// - **[8d1b057ec](facebook/react@8d1b057ec )**: [Flight] Minor error handling fixes ([facebook#25151](facebook/react#25151)) //<Sebastian Markbåge>// - **[9ff738f53](facebook/react@9ff738f53 )**: [devtools][easy] Fix flow type ([facebook#25147](facebook/react#25147)) //<Tianyu Yao>// - **[0de3ddf56](facebook/react@0de3ddf56 )**: Remove Symbol Polyfill (again) ([facebook#25144](facebook/react#25144)) //<Ricky>// - **[b36f72235](facebook/react@b36f72235 )**: Remove ReactFiberFlags MountLayoutDev and MountPassiveDev ([facebook#25091](facebook/react#25091)) //<Samuel Susla>// - **[b6978bc38](facebook/react@b6978bc38 )**: experimental_use(promise) ([facebook#25084](facebook/react#25084)) //<Andrew Clark>// - **[11ed7010c](facebook/react@11ed7010c )**: [Transition Tracing] onMarkerIncomplete - Tracing Marker/Suspense Boundary Deletions ([facebook#24885](facebook/react#24885)) //<Luna Ruan>// - **[b79894259](facebook/react@b79894259 )**: [Flight] Add support for Webpack Async Modules ([facebook#25138](facebook/react#25138)) //<Sebastian Markbåge>// - **[c8b778b7f](facebook/react@c8b778b7f )**: Fix typo: supportsMicrotask -> supportsMicrotasks ([facebook#25142](facebook/react#25142)) //<kwzr>// - **[d0f396651](facebook/react@d0f396651 )**: Allow functions to be used as module references ([facebook#25137](facebook/react#25137)) //<Sebastian Markbåge>// - **[38c5d8a03](facebook/react@38c5d8a03 )**: Test the node-register hooks in unit tests ([facebook#25132](facebook/react#25132)) //<Sebastian Markbåge>// - **[3f70e68ce](facebook/react@3f70e68ce )**: Return closestInstance in `getInspectorDataForViewAtPoint` ([facebook#25118](facebook/react#25118)) //<Tianyu Yao>// - **[3d443cad7](facebook/react@3d443cad7 )**: Update fixtures/flight to webpack 5 ([facebook#25115](facebook/react#25115)) //<Tim Neutkens>// - **[5d1ce6513](facebook/react@5d1ce6513 )**: Align StrictMode behaviour with production ([facebook#25049](facebook/react#25049)) //<Samuel Susla>// - **[9e67e7a31](facebook/react@9e67e7a31 )**: Scaffolding for useMemoCache hook ([facebook#25123](facebook/react#25123)) //<Joseph Savona>// - **[19e9a4c68](facebook/react@19e9a4c68 )**: Add missing createServerContext for experimental shared subset ([facebook#25114](facebook/react#25114)) //<Jiachi Liu>// - **[6ef466c68](facebook/react@6ef466c68 )**: make preamble and postamble types explicit and fix typo ([facebook#25102](facebook/react#25102)) //<Josh Story>// - **[796d31809](facebook/react@796d31809 )**: Implement basic stylesheet Resources for react-dom ([facebook#25060](facebook/react#25060)) //<Josh Story>// - **[32baab38f](facebook/react@32baab38f )**: [Transition Tracing] Add Tag Field to Marker Instance ([facebook#25085](facebook/react#25085)) //<Luna Ruan>// - **[8ef3a7c08](facebook/react@8ef3a7c08 )**: Resume immediately pinged fiber without unwinding ([facebook#25074](facebook/react#25074)) //<Andrew Clark>// - **[7bcc68772](facebook/react@7bcc68772 )**: Remove argument committedLanes from reappearLayoutEffects and recursivelyTraverseReappearLayoutEffects ([facebook#25080](facebook/react#25080)) //<Samuel Susla>// - **[ca990e9a7](facebook/react@ca990e9a7 )**: Add API to force Scheduler to yield for macrotask ([facebook#25044](facebook/react#25044)) //<Andrew Clark>// - **[b4204ede6](facebook/react@b4204ede6 )**: Clean up unused Deletion flag ([facebook#24992](facebook/react#24992)) //<Andrew Clark>// - **[e193be87e](facebook/react@e193be87e )**: [Transition Tracing] Add Offscreen Test ([facebook#25035](facebook/react#25035)) //<Luna Ruan>// - **[9fcaf88d5](facebook/react@9fcaf88d5 )**: Remove rootContainerInstance from unnecessary places ([facebook#25024](facebook/react#25024)) //<Sebastian Markbåge>// - **[80f3d8819](facebook/react@80f3d8819 )**: Mount/unmount passive effects when Offscreen visibility changes ([facebook#24977](facebook/react#24977)) //<Andrew Clark>// Changelog: [General][Changed] - React Native sync for revisions 4ea064e...c28f313 Reviewed By: rickhanlonii Differential Revision: D39384898 fbshipit-source-id: 20b080a53851d6dd9d522c8468dd02aab9ba76db
 <h3>Snyk has created this PR to upgrade react from 19.0.0 to 19.1.0.</h3> :information_source: Keep your dependencies up-to-date. This makes it easier to fix existing vulnerabilities and to more quickly identify and fix newly disclosed vulnerabilities when they affect your project. <hr/> - The recommended version is **78 versions** ahead of your current version. - The recommended version was released **22 days ago**. <details> <summary><b>Release notes</b></summary> <br/> <details> <summary>Package name: <b>react</b></summary> <ul> <li> <b>19.1.0</b> - <a href="https://redirect.github.com/facebook/react/releases/tag/v19.1.0">2025-03-28</a></br><h3>Owner Stack</h3> <p>An Owner Stack is a string representing the components that are directly responsible for rendering a particular component. You can log Owner Stacks when debugging or use Owner Stacks to enhance error overlays or other development tools. Owner Stacks are only available in development builds. Component Stacks in production are unchanged.</p> <ul> <li>An Owner Stack is a development-only stack trace that helps identify which components are responsible for rendering a particular component. An Owner Stack is distinct from a Component Stacks, which shows the hierarchy of components leading to an error.</li> <li>The <a href="https://react.dev/reference/react/captureOwnerStack" rel="nofollow">captureOwnerStack API</a> is only available in development mode and returns a Owner Stack, if available. The API can be used to enhance error overlays or log component relationships when debugging. <a href="https://redirect.github.com/facebook/react/pull/29923" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29923/hovercard">#29923</a>, <a href="https://redirect.github.com/facebook/react/pull/32353" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32353/hovercard">#32353</a>, <a href="https://redirect.github.com/facebook/react/pull/30306" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30306/hovercard">#30306</a>,<br> <a href="https://redirect.github.com/facebook/react/pull/32538" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32538/hovercard">#32538</a>, <a href="https://redirect.github.com/facebook/react/pull/32529" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32529/hovercard">#32529</a>, <a href="https://redirect.github.com/facebook/react/pull/32538" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32538/hovercard">#32538</a></li> </ul> <h3>React</h3> <ul> <li>Enhanced support for Suspense boundaries to be used anywhere, including the client, server, and during hydration. <a href="https://redirect.github.com/facebook/react/pull/32069" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32069/hovercard">#32069</a>, <a href="https://redirect.github.com/facebook/react/pull/32163" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32163/hovercard">#32163</a>, <a href="https://redirect.github.com/facebook/react/pull/32224" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32224/hovercard">#32224</a>, <a href="https://redirect.github.com/facebook/react/pull/32252" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32252/hovercard">#32252</a></li> <li>Reduced unnecessary client rendering through improved hydration scheduling <a href="https://redirect.github.com/facebook/react/pull/31751" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31751/hovercard">#31751</a></li> <li>Increased priority of client rendered Suspense boundaries <a href="https://redirect.github.com/facebook/react/pull/31776" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31776/hovercard">#31776</a></li> <li>Fixed frozen fallback states by rendering unfinished Suspense boundaries on the client. <a href="https://redirect.github.com/facebook/react/pull/31620" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31620/hovercard">#31620</a></li> <li>Reduced garbage collection pressure by improving Suspense boundary retries. <a href="https://redirect.github.com/facebook/react/pull/31667" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31667/hovercard">#31667</a></li> <li>Fixed erroneous “Waiting for Paint” log when the passive effect phase was not delayed <a href="https://redirect.github.com/facebook/react/pull/31526" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31526/hovercard">#31526</a></li> <li>Fixed a regression causing key warnings for flattened positional children in development mode. <a href="https://redirect.github.com/facebook/react/pull/32117" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32117/hovercard">#32117</a></li> <li>Updated <code>useId</code> to use valid CSS selectors, changing format from <code>:r123:</code> to <code>«r123»</code>. <a href="https://redirect.github.com/facebook/react/pull/32001" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32001/hovercard">#32001</a></li> <li>Added a dev-only warning for null/undefined created in useEffect, useInsertionEffect, and useLayoutEffect. <a href="https://redirect.github.com/facebook/react/pull/32355" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32355/hovercard">#32355</a></li> <li>Fixed a bug where dev-only methods were exported in production builds. React.act is no longer available in production builds. <a href="https://redirect.github.com/facebook/react/pull/32200" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32200/hovercard">#32200</a></li> <li>Improved consistency across prod and dev to improve compatibility with Google Closure Complier and bindings <a href="https://redirect.github.com/facebook/react/pull/31808" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31808/hovercard">#31808</a></li> <li>Improve passive effect scheduling for consistent task yielding. <a href="https://redirect.github.com/facebook/react/pull/31785" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31785/hovercard">#31785</a></li> <li>Fixed asserts in React Native when passChildrenWhenCloningPersistedNodes is enabled for OffscreenComponent rendering. <a href="https://redirect.github.com/facebook/react/pull/32528" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32528/hovercard">#32528</a></li> <li>Fixed component name resolution for Portal <a href="https://redirect.github.com/facebook/react/pull/32640" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32640/hovercard">#32640</a></li> <li>Added support for beforetoggle and toggle events on the dialog element. <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="2882132160" data-permission-text="Title is private" data-url="https://github.com/facebook/react/issues/32479" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32479/hovercard" href="https://redirect.github.com/facebook/react/pull/32479">#32479</a> <a href="https://redirect.github.com/facebook/react/pull/32479" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32479/hovercard">#32479</a></li> </ul> <h3>React DOM</h3> <ul> <li>Fixed double warning when the <code>href</code> attribute is an empty string <a href="https://redirect.github.com/facebook/react/pull/31783" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31783/hovercard">#31783</a></li> <li>Fixed an edge case where <code>getHoistableRoot()</code> didn’t work properly when the container was a Document <a href="https://redirect.github.com/facebook/react/pull/32321" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32321/hovercard">#32321</a></li> <li>Removed support for using HTML comments (e.g. <code><!-- --></code>) as a DOM container. <a href="https://redirect.github.com/facebook/react/pull/32250" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32250/hovercard">#32250</a></li> <li>Added support for <code><script></code> and <code><template></code> tags to be nested within <code><select></code> tags. <a href="https://redirect.github.com/facebook/react/pull/31837" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31837/hovercard">#31837</a></li> <li>Fixed responsive images to be preloaded as HTML instead of headers <a href="https://redirect.github.com/facebook/react/pull/32445" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32445/hovercard">#32445</a></li> </ul> <h3>use-sync-external-store</h3> <ul> <li>Added <code>exports</code> field to <code>package.json</code> for <code>use-sync-external-store</code> to support various entrypoints. <a href="https://redirect.github.com/facebook/react/pull/25231" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25231/hovercard">#25231</a></li> </ul> <h3>React Server Components</h3> <ul> <li>Added <code>unstable_prerender</code>, a new experimental API for prerendering React Server Components on the server <a href="https://redirect.github.com/facebook/react/pull/31724" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31724/hovercard">#31724</a></li> <li>Fixed an issue where streams would hang when receiving new chunks after a global error <a href="https://redirect.github.com/facebook/react/pull/31840" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31840/hovercard">#31840</a>, <a href="https://redirect.github.com/facebook/react/pull/31851" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31851/hovercard">#31851</a></li> <li>Fixed an issue where pending chunks were counted twice. <a href="https://redirect.github.com/facebook/react/pull/31833" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31833/hovercard">#31833</a></li> <li>Added support for streaming in edge environments <a href="https://redirect.github.com/facebook/react/pull/31852" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31852/hovercard">#31852</a></li> <li>Added support for sending custom error names from a server so that they are available in the client for console replaying. <a href="https://redirect.github.com/facebook/react/pull/32116" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32116/hovercard">#32116</a></li> <li>Updated the server component wire format to remove IDs for hints and console.log because they have no return value <a href="https://redirect.github.com/facebook/react/pull/31671" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31671/hovercard">#31671</a></li> <li>Exposed <code>registerServerReference</code> in client builds to handle server references in different environments. <a href="https://redirect.github.com/facebook/react/pull/32534" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32534/hovercard">#32534</a></li> <li>Added react-server-dom-parcel package which integrates Server Components with the <a href="https://parceljs.org/" rel="nofollow">Parcel bundler</a> <a href="https://redirect.github.com/facebook/react/pull/31725" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31725/hovercard">#31725</a>, <a href="https://redirect.github.com/facebook/react/pull/32132" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32132/hovercard">#32132</a>, <a href="https://redirect.github.com/facebook/react/pull/31799" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31799/hovercard">#31799</a>, <a href="https://redirect.github.com/facebook/react/pull/32294" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/32294/hovercard">#32294</a>, <a href="https://redirect.github.com/facebook/react/pull/31741" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31741/hovercard">#31741</a></li> </ul> </li> <li> <b>19.1.0-canary-ff628334-20250205</b> - 2025-02-06 </li> <li> <b>19.1.0-canary-fcb4e0f1-20250219</b> - 2025-02-20 </li> <li> <b>19.1.0-canary-fc8a898d-20241226</b> - 2024-12-27 </li> <li> <b>19.1.0-canary-fbcda19a-20250317</b> - 2025-03-17 </li> <li> <b>19.1.0-canary-f9d78089-20250306</b> - 2025-03-07 </li> <li> <b>19.1.0-canary-f83903bf-20250212</b> - 2025-02-12 </li> <li> <b>19.1.0-canary-f457d0b4-20250313</b> - 2025-03-13 </li> <li> <b>19.1.0-canary-f0edf41e-20250115</b> - 2025-01-14 </li> <li> <b>19.1.0-canary-ef979d47-20241218</b> - 2024-12-18 </li> <li> <b>19.1.0-canary-ef4bc8b4-20250328</b> - 2025-03-28 </li> <li> <b>19.1.0-canary-ebc22ef7-20250225</b> - 2025-02-26 </li> <li> <b>19.1.0-canary-e670e72f-20250214</b> - 2025-02-14 </li> <li> <b>19.1.0-canary-e1e74071-20250321</b> - 2025-03-21 </li> <li> <b>19.1.0-canary-e06c72fc-20241215</b> - 2024-12-16 </li> <li> <b>19.1.0-canary-e03ac20f-20250305</b> - 2025-03-05 </li> <li> <b>19.1.0-canary-de82912e-20241220</b> - 2024-12-20 </li> <li> <b>19.1.0-canary-de1eaa26-20250124</b> - 2025-01-24 </li> <li> <b>19.1.0-canary-db7dfe05-20250319</b> - 2025-03-19 </li> <li> <b>19.1.0-canary-d85cf3e5-20250205</b> - 2025-02-05 </li> <li> <b>19.1.0-canary-d55cc79b-20250228</b> - 2025-02-28 </li> <li> <b>19.1.0-canary-d46b04a2-20250117</b> - 2025-01-17 </li> <li> <b>19.1.0-canary-d4287258-20241217</b> - 2024-12-17 </li> <li> <b>19.1.0-canary-d331ba04-20250307</b> - 2025-03-10 </li> <li> <b>19.1.0-canary-cd90a4d8-20250210</b> - 2025-02-11 </li> <li> <b>19.1.0-canary-cbbe8666-20250213</b> - 2025-02-13 </li> <li> <b>19.1.0-canary-cabd8a0e-20250113</b> - 2025-01-13 </li> <li> <b>19.1.0-canary-c69a5fc5-20250318</b> - 2025-03-18 </li> <li> <b>19.1.0-canary-c492f975-20250128</b> - 2025-01-29 </li> <li> <b>19.1.0-canary-c01b8058-20241229</b> - 2024-12-30 </li> <li> <b>19.1.0-canary-bb9a24d9-20250130</b> - 2025-01-30 </li> <li> <b>19.1.0-canary-b3a95caf-20250113</b> - 2025-01-14 </li> <li> <b>19.1.0-canary-b158439a-20250115</b> - 2025-01-15 </li> <li> <b>19.1.0-canary-ae9017ce-20250122</b> - 2025-01-23 </li> <li> <b>19.1.0-canary-a84862db-20250218</b> - 2025-02-19 </li> <li> <b>19.1.0-canary-a4f9bd58-20250319</b> - 2025-03-20 </li> <li> <b>19.1.0-canary-a4b2d0d5-20250203</b> - 2025-02-03 </li> <li> <b>19.1.0-canary-9ff42a87-20250130</b> - 2025-01-31 </li> <li> <b>19.1.0-canary-9eabb373-20250124</b> - 2025-01-27 </li> <li> <b>19.1.0-canary-9b62ee71-20250122</b> - 2025-01-22 </li> <li> <b>19.1.0-canary-97d79495-20241223</b> - 2024-12-24 </li> <li> <b>19.1.0-canary-9463d51e-20241219</b> - 2024-12-19 </li> <li> <b>19.1.0-canary-93b58361-20250209</b> - 2025-02-10 </li> <li> <b>19.1.0-canary-8a7b487e-20250218</b> - 2025-02-18 </li> <li> <b>19.1.0-canary-8759c5c8-20250207</b> - 2025-02-07 </li> <li> <b>19.1.0-canary-7eb8234f-20241218</b> - 2024-12-18 </li> <li> <b>19.1.0-canary-7b402084-20250107</b> - 2025-01-07 </li> <li> <b>19.1.0-canary-74ea0c73-20250109</b> - 2025-01-09 </li> <li> <b>19.1.0-canary-740a4f7a-20250325</b> - 2025-03-25 </li> <li> <b>19.1.0-canary-7130d0c6-20241212</b> - 2024-12-12 </li> <li> <b>19.1.0-canary-6aa8254b-20250312</b> - 2025-03-12 </li> <li> <b>19.1.0-canary-694d3e1a-20241231</b> - 2025-01-01 </li> <li> <b>19.1.0-canary-6907aa2a-20241220</b> - 2024-12-23 </li> <li> <b>19.1.0-canary-662957cc-20250221</b> - 2025-02-21 </li> <li> <b>19.1.0-canary-62208bee-20250102</b> - 2025-01-02 </li> <li> <b>19.1.0-canary-5b51a2b9-20250116</b> - 2025-01-16 </li> <li> <b>19.1.0-canary-540efebc-20250112</b> - 2025-01-12 </li> <li> <b>19.1.0-canary-5398b711-20250314</b> - 2025-03-14 </li> <li> <b>19.1.0-canary-518d06d2-20241219</b> - 2024-12-19 </li> <li> <b>19.1.0-canary-4dff0e62-20241213</b> - 2024-12-13 </li> <li> <b>19.1.0-canary-4632e36a-20250216</b> - 2025-02-17 </li> <li> <b>19.1.0-canary-443b7ff2-20250303</b> - 2025-03-04 </li> <li> <b>19.1.0-canary-4280563b-20250326</b> - 2025-03-27 </li> <li> <b>19.1.0-canary-42687267-20250108</b> - 2025-01-08 </li> <li> <b>19.1.0-canary-3ce77d55-20250106</b> - 2025-01-06 </li> <li> <b>19.1.0-canary-3b009b4c-20250102</b> - 2025-01-03 </li> <li> <b>19.1.0-canary-37906d4d-20250127</b> - 2025-01-28 </li> <li> <b>19.1.0-canary-32b0cad8-20250213</b> - 2025-02-13 </li> <li> <b>19.1.0-canary-313332d1-20250326</b> - 2025-03-26 </li> <li> <b>19.1.0-canary-2980f277-20250301</b> - 2025-03-03 </li> <li> <b>19.1.0-canary-25677265-20250224</b> - 2025-02-24 </li> <li> <b>19.1.0-canary-22e39ea7-20250225</b> - 2025-02-25 </li> <li> <b>19.1.0-canary-18eaf51b-20250118</b> - 2025-01-20 </li> <li> <b>19.1.0-canary-130095f7-20241212</b> - 2024-12-12 </li> <li> <b>19.1.0-canary-0ca3deeb-20250311</b> - 2025-03-11 </li> <li> <b>19.1.0-canary-0a82580b-20250203</b> - 2025-02-04 </li> <li> <b>19.1.0-canary-056073de-20250109</b> - 2025-01-10 </li> <li> <b>19.1.0-canary-029e8bd6-20250306</b> - 2025-03-06 </li> <li> <b>19.0.0</b> - <a href="https://redirect.github.com/facebook/react/releases/tag/v19.0.0">2024-12-05</a></br><p>Below is a list of all new features, APIs, deprecations, and breaking changes. Read <a href="https://react.dev/blog/2024/04/25/react-19" rel="nofollow">React 19 release post</a> and <a href="https://react.dev/blog/2024/04/25/react-19-upgrade-guide" rel="nofollow">React 19 upgrade guide</a> for more information.</p> <blockquote> <p>Note: To help make the upgrade to React 19 easier, we’ve published a [email protected] 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.</p> </blockquote> <h2>New Features</h2> <h3>React</h3> <ul> <li>Actions: <code>startTransition</code> can now accept async functions. Functions passed to <code>startTransition</code> 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 <code>fetch()</code> in the pending state, and provides support for error handling, and optimistic updates.</li> <li><code>useActionState</code>: 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 <code>action</code> prop to support progressive enhancement in forms.</li> <li><code>useOptimistic</code>: 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.</li> <li><code>use</code>: is a new API that allows reading resources in render. In React 19, <code>use</code> accepts a promise or Context. If provided a promise, <code>use</code> will suspend until a value is resolved. <code>use</code> can only be used in render but can be called conditionally.</li> <li><code>ref</code> as a prop: Refs can now be used as props, removing the need for <code>forwardRef</code>.</li> <li><strong>Suspense sibling pre-warming</strong>: 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.</li> </ul> <h3>React DOM Client</h3> <ul> <li><code><form> action</code> prop: Form Actions allow you to manage forms automatically and integrate with <code>useFormStatus</code>. When a <code><form> action</code> succeeds, React will automatically reset the form for uncontrolled components. The form can be reset manually with the new <code>requestFormReset</code> API.</li> <li><code><button> and <input> formAction</code> prop: Actions can be passed to the <code>formAction</code> prop to configure form submission behavior. This allows using different Actions depending on the input.</li> <li><code>useFormStatus</code>: is a new hook that provides the status of the parent <code><form> action</code>, as if the form was a Context provider. The hook returns the values: <code>pending</code>, <code>data</code>, <code>method</code>, and <code>action</code>.</li> <li>Support for Document Metadata: We’ve added support for rendering document metadata tags in components natively. React will automatically hoist them into the <code><head></code> section of the document.</li> <li>Support for Stylesheets: React 19 will ensure stylesheets are inserted into the <code><head></code> on the client before revealing the content of a Suspense boundary that depends on that stylesheet.</li> <li>Support for async scripts: Async scripts can be rendered anywhere in the component tree and React will handle ordering and deduplication.</li> <li>Support for preloading resources: React 19 ships with <code>preinit</code>, <code>preload</code>, <code>prefetchDNS</code>, and <code>preconnect</code> 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.</li> </ul> <h3>React DOM Server</h3> <ul> <li>Added <code>prerender</code> and <code>prerenderToNodeStream</code> APIs for static site generation. They are designed to work with streaming environments like Node.js Streams and Web Streams. Unlike <code>renderToString</code>, they wait for data to load for HTML generation.</li> </ul> <h3>React Server Components</h3> <ul> <li>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 <a href="https://19.react.dev/reference/rsc/server-components" rel="nofollow">docs</a> for how to support React Server Components.</li> </ul> <h2>Deprecations</h2> <ul> <li>Deprecated: <code>element.ref</code> access: React 19 supports ref as a prop, so we’re deprecating <code>element.ref</code> in favor of <code>element.props.ref</code>. Accessing will result in a warning.</li> <li><code>react-test-renderer</code>: 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 @ testinglibrary.com/docs/react-testing-library/intro/) or @ testingesting-library.com/docs/react-native-testing-library/intro)</li> </ul> <h2>Breaking Changes</h2> <p>React 19 brings in a number of breaking changes, including the removals of long-deprecated APIs. We recommend first upgrading to <code>18.3.1</code>, where we've added additional deprecation warnings. Check out the <a href="https://19.react.dev/blog/2024/04/25/react-19-upgrade-guide" rel="nofollow">upgrade guide</a> for more details and guidance on codemodding.</p> <h3>React</h3> <ul> <li>New JSX Transform is now required: We introduced <a href="https://legacy.reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html" rel="nofollow">a new JSX transform</a> 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.</li> <li>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 <code>onUncaughtError</code> and <code>onCaughtError</code> methods to <code>createRoot</code> and <code>hydrateRoot</code> to customize this error handling.</li> <li>Removed: <code>propTypes</code>: Using <code>propTypes</code> will now be silently ignored. If required, we recommend migrating to TypeScript or another type-checking solution.</li> <li>Removed: <code>defaultProps</code> for functions: ES6 default parameters can be used in place. Class components continue to support <code>defaultProps</code> since there is no ES6 alternative.</li> <li>Removed: <code>contextTypes</code> and <code>getChildContext</code>: Legacy Context for class components has been removed in favor of the <code>contextType</code> API.</li> <li>Removed: string refs: Any usage of string refs need to be migrated to ref callbacks.</li> <li>Removed: Module pattern factories: A rarely used pattern that can be migrated to regular functions.</li> <li>Removed: <code>React.createFactory</code>: Now that JSX is broadly supported, all <code>createFactory</code> usage can be migrated to JSX components.</li> <li>Removed: <code>react-test-renderer/shallow</code>: This has been a re-export of <a href="https://redirect.github.com/enzymejs/react-shallow-renderer">react-shallow-renderer</a> since React 18. If needed, you can continue to use the third-party package directly. We recommend using @ testinglibrary.com/docs/react-testing-library/intro/) or @ testingesting-library.com/docs/react-native-testing-library/intro) instead.</li> </ul> <h3>React DOM</h3> <ul> <li>Removed: <code>react-dom/test-utils</code>: We’ve moved <code>act</code> from <code>react-dom/test-utils</code> to react. All other utilities have been removed.</li> <li>Removed: <code>ReactDOM</code>.<code>render</code>, <code>ReactDOM</code>.<code>hydrate</code>: These have been removed in favor of the concurrent equivalents: <code>ReactDOM</code>.<code>createRoot</code> and <code>ReactDOM.hydrateRoot</code>.</li> <li>Removed: <code>unmountComponentAtNode</code>: Removed in favor of <code>root.unmount()</code>.</li> <li>Removed: <code>ReactDOM</code>.<code>findDOMNode</code>: You can replace <code>ReactDOM</code>.<code>findDOMNode</code> with DOM Refs.</li> </ul> <h2>Notable Changes</h2> <h3>React</h3> <ul> <li><code><Context></code> as a provider: You can now render <code><Context></code> as a provider instead of <code><Context.Provider></code>.</li> <li>Cleanup functions for refs: When the component unmounts, React will call the cleanup function returned from the ref callback.</li> <li><code>useDeferredValue</code> initial value argument: When provided, <code>useDeferredValue</code> will return the initial value for the initial render of a component, then schedule a re-render in the background with the <code>deferredValue</code> returned.</li> <li>Support for Custom Elements: React 19 now passes all tests on <a href="https://custom-elements-everywhere.com/" rel="nofollow">Custom Elements Everywhere</a>.</li> <li>StrictMode changes: <code>useMemo</code> and <code>useCallback</code> 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.</li> <li>UMD builds removed: To load React 19 with a script tag, we recommend using an ESM-based CDN such as <a href="http://esm.sh" rel="nofollow">esm.sh</a>.</li> </ul> <h3>React DOM</h3> <ul> <li>Diffs for hydration errors: In the case of a mismatch, React 19 logs a single error with a diff of the mismatched content.</li> <li>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.</li> </ul> <h2>TypeScript Changes</h2> <p>The most common changes can be codemodded with <code>npx types-react-codemod@latest preset-19 ./path-to-your-react-ts-files</code>.</p> <ul> <li>Removed deprecated TypeScript types: <ul> <li><code>ReactChild</code> (replacement: <code>React.ReactElement | number | string)</code></li> <li><code>ReactFragment</code> (replacement: <code>Iterable<React.ReactNode></code>)</li> <li><code>ReactNodeArray</code> (replacement: <code>ReadonlyArray<React.ReactNode></code>)</li> <li><code>ReactText</code> (replacement: <code>number | string</code>)</li> <li><code>VoidFunctionComponent</code> (replacement: <code>FunctionComponent</code>)</li> <li><code>VFC</code> (replacement: <code>FC</code>)</li> <li>Moved to <code>prop-types</code>: <code>Requireable</code>, <code>ValidationMap</code>, <code>Validator</code>, <code>WeakValidationMap</code></li> <li>Moved to <code>create-react-class</code>: <code>ClassicComponentClass</code>, <code>ClassicComponent</code>, <code>ClassicElement</code>, <code>ComponentSpec</code>, <code>Mixin</code>, <code>ReactChildren</code>, <code>ReactHTML</code>, <code>ReactSVG</code>, <code>SFCFactory</code></li> </ul> </li> <li>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.</li> <li>Require initial argument to <code>useRef</code>: The initial argument is now required to match <code>useState</code>, <code>createContext</code> etc</li> <li>Refs are mutable by default: Ref objects returned from <code>useRef()</code> 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.</li> <li>Strict <code>ReactElement</code> typing: The props of React elements now default to <code>unknown</code> instead of <code>any</code> if the element is typed as <code>ReactElement</code></li> <li>JSX namespace in TypeScript: The global <code>JSX</code> namespace is removed to improve interoperability with other libraries using JSX. Instead, the JSX namespace is available from the React package: <code>import { JSX } from 'react'</code></li> <li>Better <code>useReducer</code> typings: Most <code>useReducer</code> usage should not require explicit type arguments.<br> For example, <div class="highlight highlight-source-diff notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="-useReducer<React.Reducer<State, Action>>(reducer) +useReducer(reducer) "><pre><span class="pl-md"><span class="pl-md">-</span>useReducer<React.Reducer<State, Action>>(reducer) </span> <span class="pl-mi1"><span class="pl-mi1">+</span>useReducer(reducer) </span></pre></div> or <div class="highlight highlight-source-diff notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="-useReducer<React.Reducer<State, Action>>(reducer) +useReducer<State, [Action]>(reducer)"><pre><span class="pl-md"><span class="pl-md">-</span>useReducer<React.Reducer<State, Action>>(reducer) </span> <span class="pl-mi1"><span class="pl-mi1">+</span>useReducer<State, [Action]>(reducer)</span></pre></div> </li> </ul> <h2>All Changes</h2> <h3>React</h3> <ul> <li>Add support for async Actions (<a href="https://redirect.github.com/facebook/react/pull/26621" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26621/hovercard">#26621</a>, <a href="https://redirect.github.com/facebook/react/pull/26726" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26726/hovercard">#26726</a>, <a href="https://redirect.github.com/facebook/react/pull/28078" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28078/hovercard">#28078</a>, <a href="https://redirect.github.com/facebook/react/pull/28097" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28097/hovercard">#28097</a>, <a href="https://redirect.github.com/facebook/react/pull/29226" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29226/hovercard">#29226</a>, <a href="https://redirect.github.com/facebook/react/pull/29618" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29618/hovercard">#29618</a>, <a href="https://redirect.github.com/facebook/react/pull/29670" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29670/hovercard">#29670</a>, <a href="https://redirect.github.com/facebook/react/pull/26716" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26716/hovercard">#26716</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a> and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sebmarkbage/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sebmarkbage">@ sebmarkbage</a>)</li> <li>Add <code>useActionState()</code> hook to update state based on the result of a Form Action (<a href="https://redirect.github.com/facebook/react/pull/27270" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27270/hovercard">#27270</a>, <a href="https://redirect.github.com/facebook/react/pull/27278" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27278/hovercard">#27278</a>, <a href="https://redirect.github.com/facebook/react/pull/27309" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27309/hovercard">#27309</a>, <a href="https://redirect.github.com/facebook/react/pull/27302" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27302/hovercard">#27302</a>, <a href="https://redirect.github.com/facebook/react/pull/27307" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27307/hovercard">#27307</a>, <a href="https://redirect.github.com/facebook/react/pull/27366" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27366/hovercard">#27366</a>, <a href="https://redirect.github.com/facebook/react/pull/27370" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27370/hovercard">#27370</a>, <a href="https://redirect.github.com/facebook/react/pull/27321" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27321/hovercard">#27321</a>, <a href="https://redirect.github.com/facebook/react/pull/27374" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27374/hovercard">#27374</a>, <a href="https://redirect.github.com/facebook/react/pull/27372" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27372/hovercard">#27372</a>, <a href="https://redirect.github.com/facebook/react/pull/27397" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27397/hovercard">#27397</a>, <a href="https://redirect.github.com/facebook/react/pull/27399" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27399/hovercard">#27399</a>, <a href="https://redirect.github.com/facebook/react/pull/27460" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27460/hovercard">#27460</a>, <a href="https://redirect.github.com/facebook/react/pull/28557" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28557/hovercard">#28557</a>, <a href="https://redirect.github.com/facebook/react/pull/27570" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27570/hovercard">#27570</a>, <a href="https://redirect.github.com/facebook/react/pull/27571" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27571/hovercard">#27571</a>, <a href="https://redirect.github.com/facebook/react/pull/28631" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28631/hovercard">#28631</a>, <a href="https://redirect.github.com/facebook/react/pull/28788" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28788/hovercard">#28788</a>, <a href="https://redirect.github.com/facebook/react/pull/29694" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29694/hovercard">#29694</a>, <a href="https://redirect.github.com/facebook/react/pull/29695" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29695/hovercard">#29695</a>, <a href="https://redirect.github.com/facebook/react/pull/29694" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29694/hovercard">#29694</a>, <a href="https://redirect.github.com/facebook/react/pull/29665" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/29665/hovercard">#29665</a>, <a href="https://redirect.github.com/facebook/react/pull/28232" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28232/hovercard">#28232</a>, <a href="https://redirect.github.com/facebook/react/pull/28319" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28319/hovercard">#28319</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/eps1lon/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/eps1lon">@ eps1lon</a>, and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/rickhanlonii/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/rickhanlonii">@ rickhanlonii</a>)</li> <li>Add <code>use()</code> API to read resources in render (<a href="https://redirect.github.com/facebook/react/pull/25084" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25084/hovercard">#25084</a>, <a href="https://redirect.github.com/facebook/react/pull/25202" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25202/hovercard">#25202</a>, <a href="https://redirect.github.com/facebook/react/pull/25207" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25207/hovercard">#25207</a>, <a href="https://redirect.github.com/facebook/react/pull/25214" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25214/hovercard">#25214</a>, <a href="https://redirect.github.com/facebook/react/pull/25226" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25226/hovercard">#25226</a>, <a href="https://redirect.github.com/facebook/react/pull/25247" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25247/hovercard">#25247</a>, <a href="https://redirect.github.com/facebook/react/pull/25539" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25539/hovercard">#25539</a>, <a href="https://redirect.github.com/facebook/react/pull/25538" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25538/hovercard">#25538</a>, <a href="https://redirect.github.com/facebook/react/pull/25537" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25537/hovercard">#25537</a>, <a href="https://redirect.github.com/facebook/react/pull/25543" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25543/hovercard">#25543</a>, <a href="https://redirect.github.com/facebook/react/pull/25561" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25561/hovercard">#25561</a>, <a href="https://redirect.github.com/facebook/react/pull/25620" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25620/hovercard">#25620</a>, <a href="https://redirect.github.com/facebook/react/pull/25615" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25615/hovercard">#25615</a>, <a href="https://redirect.github.com/facebook/react/pull/25922" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25922/hovercard">#25922</a>, <a href="https://redirect.github.com/facebook/react/pull/25641" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25641/hovercard">#25641</a>, <a href="https://redirect.github.com/facebook/react/pull/25634" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25634/hovercard">#25634</a>, <a href="https://redirect.github.com/facebook/react/pull/26232" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26232/hovercard">#26232</a>, <a href="https://redirect.github.com/facebook/react/pull/26535" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26535/hovercard">#26536</a>, <a href="https://redirect.github.com/facebook/react/pull/26739" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26739/hovercard">#26739</a>, <a href="https://redirect.github.com/facebook/react/pull/28233" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28233/hovercard">#28233</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/mofeiZ/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/mofeiZ">@ mofeiZ</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sebmarkbage/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sebmarkbage">@ sebmarkbage</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sophiebits/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sophiebits">@ sophiebits</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/eps1lon/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/eps1lon">@ eps1lon</a>, and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/hansottowirtz/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/hansottowirtz">@ hansottowirtz</a>)</li> <li>Add <code>useOptimistic()</code> hook to display mutated state optimistically during an async mutation (<a href="https://redirect.github.com/facebook/react/pull/26740" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26740/hovercard">#26740</a>, <a href="https://redirect.github.com/facebook/react/pull/26772" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26772/hovercard">#26772</a>, <a href="https://redirect.github.com/facebook/react/pull/27277" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27277/hovercard">#27277</a>, <a href="https://redirect.github.com/facebook/react/pull/27453" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27453/hovercard">#27453</a>, <a href="https://redirect.github.com/facebook/react/pull/27454" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27454/hovercard">#27454</a>, <a href="https://redirect.github.com/facebook/react/pull/27936" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27936/hovercard">#27936</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Added an <code>initialValue</code> argument to <code>useDeferredValue()</code> hook (<a href="https://redirect.github.com/facebook/react/pull/27500" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27500/hovercard">#27500</a>, <a href="https://redirect.github.com/facebook/react/pull/27509" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27509/hovercard">#27509</a>, <a href="https://redirect.github.com/facebook/react/pull/27512" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27512/hovercard">#27512</a>, <a href="https://redirect.github.com/facebook/react/pull/27888" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27888/hovercard">#27888</a>, <a href="https://redirect.github.com/facebook/react/pull/27550" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27550/hovercard">#27550</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Support refs as props, warn on <code>element.ref</code> access (<a href="https://redirect.github.com/facebook/react/pull/28348" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28348/hovercard">#28348</a>, <a href="https://redirect.github.com/facebook/react/pull/28464" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28464/hovercard">#28464</a>, <a href="https://redirect.github.com/facebook/react/pull/28731" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28731/hovercard">#28731</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Support Custom Elements (<a href="https://redirect.github.com/facebook/react/pull/22184" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/22184/hovercard">#22184</a>, <a href="https://redirect.github.com/facebook/react/pull/26524" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26524/hovercard">#26524</a>, <a href="https://redirect.github.com/facebook/react/pull/26523" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26523/hovercard">#26523</a>, <a href="https://redirect.github.com/facebook/react/pull/27511" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27511/hovercard">#27511</a>, <a href="https://redirect.github.com/facebook/react/pull/24541" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/24541/hovercard">#24541</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/josepharhar/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/josepharhar">@ josepharhar</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sebmarkbage/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sebmarkbage">@ sebmarkbage</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/gnoff/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/gnoff">@ gnoff</a> and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/eps1lon/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/eps1lon">@ eps1lon</a>)</li> <li>Add ref cleanup function (<a href="https://redirect.github.com/facebook/react/pull/25686" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25686/hovercard">#25686</a>, <a href="https://redirect.github.com/facebook/react/pull/28883" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28883/hovercard">#28883</a>, <a href="https://redirect.github.com/facebook/react/pull/28910" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28910/hovercard">#28910</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sammy-SC/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sammy-SC">@ sammy-SC</a>), <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/jackpope/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/jackpope">@ jackpope</a>, and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/kassens/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/kassens">@ kassens</a>)</li> <li>Sibling pre-rendering replaced by sibling pre-warming (<a href="https://redirect.github.com/facebook/react/pull/26380" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26380/hovercard">#26380</a>, <a href="https://redirect.github.com/facebook/react/pull/26549" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26549/hovercard">#26549</a>, <a href="https://redirect.github.com/facebook/react/pull/30761" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30761/hovercard">#30761</a>, <a href="https://redirect.github.com/facebook/react/pull/30800" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30800/hovercard">#30800</a>, <a href="https://redirect.github.com/facebook/react/pull/30762" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30762/hovercard">#30762</a>, <a href="https://redirect.github.com/facebook/react/pull/30879" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30879/hovercard">#30879</a>, <a href="https://redirect.github.com/facebook/react/pull/30934" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30934/hovercard">#30934</a>, <a href="https://redirect.github.com/facebook/react/pull/30952" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/30952/hovercard">#30952</a>, <a href="https://redirect.github.com/facebook/react/pull/31056" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31056/hovercard">#31056</a>, <a href="https://redirect.github.com/facebook/react/pull/31452" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/31452/hovercard">#31452</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sammy-SC/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sammy-SC">@ sammy-SC</a>), <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/gnoff/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/gnoff">@ gnoff</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/jackpope/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/jackpope">@ jackpope</a>, <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/rickhanlonii/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/rickhanlonii">@ rickhanlonii</a>)</li> <li>Don’t rethrow errors at the root (<a href="https://redirect.github.com/facebook/react/pull/28627" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28627/hovercard">#28627</a>, <a href="https://redirect.github.com/facebook/react/pull/28641" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28641/hovercard">#28641</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sebmarkbage/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sebmarkbage">@ sebmarkbage</a>)</li> <li>Batch sync discrete, continuous, and default lanes (<a href="https://redirect.github.com/facebook/react/pull/25700" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25700/hovercard">#25700</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/tyao1/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/tyao1">@ tyao1</a>)</li> <li>Switch <code><Context></code> to mean <code><Context.Provider></code> (<a href="https://redirect.github.com/facebook/react/pull/28226" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28226/hovercard">#28226</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/gaearon/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/gaearon">@ gaearon</a>)</li> <li>Changes to <em>StrictMode</em> <ul> <li>Handle <code>info</code>, <code>group</code>, and <code>groupCollapsed</code> in <em>StrictMode</em> logging (<a href="https://redirect.github.com/facebook/react/pull/25172" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25172/hovercard">#25172</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/timneutkens/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/timneutkens">@ timneutkens</a>)</li> <li>Refs are now attached/detached/attached in <em>StrictMode</em> (<a href="https://redirect.github.com/facebook/react/pull/25049" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25049/hovercard">#25049</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sammy-SC/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sammy-SC">@ sammy-SC</a>)</li> <li>Fix <code>useSyncExternalStore()</code> hydration in <em>StrictMode</em> (<a href="https://redirect.github.com/facebook/react/pull/26791" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26791/hovercard">#26791</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sophiebits/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sophiebits">@ sophiebits</a>)</li> <li>Always trigger <code>componentWillUnmount()</code> in <em>StrictMode</em> (<a href="https://redirect.github.com/facebook/react/pull/26842" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26842/hovercard">#26842</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/tyao1/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/tyao1">@ tyao1</a>)</li> <li>Restore double invoking <code>useState()</code> and <code>useReducer()</code> initializer functions in <em>StrictMode</em> (<a href="https://redirect.github.com/facebook/react/pull/28248" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/28248/hovercard">#28248</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/eps1lon/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/eps1lon">@ eps1lon</a>)</li> <li>Reuse memoized result from first pass (<a href="https://redirect.github.com/facebook/react/pull/25583" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25583/hovercard">#25583</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Fix <code>useId()</code> in <em>StrictMode</em> (<a href="https://redirect.github.com/facebook/react/pull/25713" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25713/hovercard">#25713</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/gnoff/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/gnoff">@ gnoff</a>)</li> <li>Add component name to <em>StrictMode</em> error messages (<a href="https://redirect.github.com/facebook/react/pull/25718" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25718/hovercard">#25718</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sammy-SC/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sammy-SC">@ sammy-SC</a>)</li> </ul> </li> <li>Add support for rendering BigInt (<a href="https://redirect.github.com/facebook/react/pull/24580" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/24580/hovercard">#24580</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/eps1lon/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/eps1lon">@ eps1lon</a>)</li> <li><code>act()</code> no longer checks <code>shouldYield</code> which can be inaccurate in test environments (<a href="https://redirect.github.com/facebook/react/pull/26317" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26317/hovercard">#26317</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Warn when keys are spread with props (<a href="https://redirect.github.com/facebook/react/pull/25697" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25697/hovercard">#25697</a>, <a href="https://redirect.github.com/facebook/react/pull/26080" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26080/hovercard">#26080</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/sebmarkbage/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/sebmarkbage">@ sebmarkbage</a> and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/kassens/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/kassens">@ kassens</a>)</li> <li>Generate sourcemaps for production build artifacts (<a href="https://redirect.github.com/facebook/react/pull/26446" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26446/hovercard">#26446</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/markerikson/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/markerikson">@ markerikson</a>)</li> <li>Improve stack diffing algorithm (<a href="https://redirect.github.com/facebook/react/pull/27132" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/27132/hovercard">#27132</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/KarimP/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/KarimP">@ KarimP</a>)</li> <li>Suspense throttling lowered from 500ms to 300ms (<a href="https://redirect.github.com/facebook/react/pull/26803" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26803/hovercard">#26803</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Lazily propagate context changes (<a href="https://redirect.github.com/facebook/react/pull/20890" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/20890/hovercard">#20890</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a> and <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/gnoff/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/gnoff">@ gnoff</a>)</li> <li>Immediately rerender pinged fiber (<a href="https://redirect.github.com/facebook/react/pull/25074" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/25074/hovercard">#25074</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Move update scheduling to microtask (<a href="https://redirect.github.com/facebook/react/pull/26512" data-hovercard-type="pull_request" data-hovercard-url="/facebook/react/pull/26512/hovercard">#26512</a> by <a class="user-mention notranslate" data-hovercard-type="user" data-hovercard-url="/users/acdlite/hovercard" data-octo-click="hovercard-link-click" data-octo-dimensions="link_type:self" href="https://redirect.github.com/acdlite">@ acdlite</a>)</li> <li>Consistently apply throttled retries (<a href="https://redirect.github.com/facebook/…
Adds experimental support to Fiber for unwrapping the value of a promise inside a component. It is not yet implemented for Server Components, but that is planned.
If promise has already resolved, the value can be unwrapped "immediately" without showing a fallback. The trick we use to implement this is to yield to the main thread (literally suspending the work loop), wait for the microtask queue to drain, then check if the promise resolved in the meantime. If so, we can resume the last attempted fiber without unwinding the stack. This functionality was implemented in previous commits.
Another feature is that the promises do not need to be cached between attempts. Because we assume idempotent execution of components, React will track the promises that were used during the previous attempt and reuse the result. You shouldn't rely on this property, but during initial render it mostly just works. Updates are trickier, though, because if you used an uncached promise, we have no way of knowing whether the underlying data has changed, so we have to unwrap the promise every time. It will still work, but it's inefficient and can lead to unnecessary fallbacks if it happens during a discrete update.
When we implement this for Server Components, this will be less of an issue because there are no updates in that environment. However, it's still better for performance to cache data requests, so the same principles largely apply.
The intention is that this will eventually be the only supported way to suspend on arbitrary promises. Throwing a promise directly will be deprecated.
Todo