Replay Client Actions After Hydration #26716
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sebmarkbage
commented
Apr 24, 2023
| @@ -105,7 +111,7 @@ const discreteReplayableEvents: Array<DOMEventName> = [ | |||
| 'change', | |||
| 'contextmenu', | |||
| 'reset', | |||
| 'submit', | |||
| // 'submit', // stopPropagation blocks the replay mechanism | |||
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This is really unfortunate and I'm not sure what the correct solution is.
We currently call stopPropagation when we might have hydrated some of the tree but not all the way to the target. We do this because we want to treat the tree as if it wasn't hydrated at all. Meaning we shouldn't call any parent event handlers if they would've been stopped.
However, this is not like "before" hydration for any other more global scripts that were inserted early or by third parties.
In this case, this blocks our event replaying handler at the root so we don't call preventDefault and it just ends up going through the javascript: URL.
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What event handlers is it trying to block? Native event handlers added by components would be added by useEffect which hasn't run at this point right?
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It could've been if it's in a parent component with a Suspense/Hydration boundary around the target.
sebmarkbage
commented
Apr 24, 2023
| } | ||
| return writeBootstrap(destination, responseState) && writeMore; |
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This lets us add more bootstrapping code in case we discover that something nested needs bootstrapping code later on. Which seems like a generally useful thing.
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sebmarkbage
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Apr 24, 2023
| } from './ReactDOMFizzInstructionSetShared'; | ||
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|
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| import {enableFormActions} from 'shared/ReactFeatureFlags'; |
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The test failures are because the hacky Fizz test runtime doesn't use the same bundling rules as we use when actually building this file so it doesn't know how to resolve the feature flags even though the prod builds do.
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For now, you could gate the tests to only run during build, like this:
// @gate !sourceThere was a problem hiding this comment.
I have an alternative strategy here #26717 that I think is probably the better solution anyway.
sophiebits
approved these changes
Apr 24, 2023
| return; | ||
| } | ||
| const form = event.target; | ||
| const submitter = event['submitter']; |
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do we need better closure externs? (do we even get anything out of advanced mode?)
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Yea, I added one for addEventListener already. Not sure we need advanced mode tbh.
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I think the only reason I made it use advanced was to avoid having to run Rollup on it to minify the symbols (though there's probably a better way to do that besides advanced mode) but it looks like we're probably going to have to run Rollup on this file anyway
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Ideally it would use the same build pipeline as every other file but there's a sequencing issue because our normal build pipeline doesn't have an easy way to do codegen. We'd have to run the build script twice with different arguments, maybe.
| // needs to be available before that happens so after construction it's too | ||
| // late. We use a temporary fake node for the duration of this event. | ||
| // TODO: FormData takes a second argument that it's the submitter but this | ||
| // is fairly new so not all browsers support it yet. Switch to that technique |
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looks like it's actually supported in all modern browsers as of this month…
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Yea but it'll take a while until everyone is on modern iOS versions and all the Samsung TV upgrade.
| i -= 3; | ||
| } | ||
| // Schedule a replay in case this unblocked something. | ||
| scheduleReplayQueueIfNeeded(formReplayingQueue); |
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does this only need to happen in the typeof action === 'function' case?
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This one is a little interesting because this might have been a case that was blocking another action that is further in the list already but has already been resolved.
| ); | ||
| } | ||
| } | ||
|
|
||
| export function retryIfBlockedOn( |
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So does this wait until all the components in a container are hydrated?
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Yea but this also gets called if it ends up deleted instead.
| }); | ||
|
|
||
| // It should've now been replayed | ||
| expect(foo).toBe('bar'); |
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make sure it's called just once?
make sure formData is captured at the time of submission?
| @@ -105,7 +111,7 @@ const discreteReplayableEvents: Array<DOMEventName> = [ | |||
| 'change', | |||
| 'contextmenu', | |||
| 'reset', | |||
| 'submit', | |||
| // 'submit', // stopPropagation blocks the replay mechanism | |||
There was a problem hiding this comment.
What event handlers is it trying to block? Native event handlers added by components would be added by useEffect which hasn't run at this point right?
This was referenced Apr 24, 2023
…ates Then try to replay any action that got unblocked. The hard part comes from the it might be more than one React instance that shares this queue.
This blocks the action replaying mechanism because it calls stopPropagation.
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EdisonVan
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Apr 15, 2024
We used to have Event Replaying for any kind of Discrete event where we'd track any event after hydrateRoot and before the async code/data has loaded in to hydrate the target. However, this didn't really work out because code inside event handlers are expected to be able to synchronously read the state of the world at the time they're invoked. If we replay discrete events later, the mutable state around them like selection or form state etc. may have changed. This limitation doesn't apply to Client Actions: - They're expected to be async functions that themselves work asynchronously. They're conceptually also in the "navigation" events that happen after the "submit" events so they're already not synchronously even before the first `await`. - They're expected to operate mostly on the FormData as input which we can snapshot at the time of the event. This PR adds a bit of inline script to the Fizz runtime (or external runtime) to track any early submit events on the page - but only if the action URL is our placeholder `javascript:` URL. We track a queue of these on `document.$$reactFormReplay`. Then we replay them in order as they get hydrated and we get a handle on the Client Action function. I add the runtime to the `bootstrapScripts` phase in Fizz which is really technically a little too late, because on a large page, it might take a while to get to that script even if you have displayed the form. However, that's also true for external runtime. So there's a very short window we might miss an event but it's good enough and better than risking blocking display on this script. The main thing that makes the replaying difficult to reason about is that we can have multiple instance of React using this same queue. This would be very usual but you could have two different Reacts SSR:ing different parts of the tree and using around the same version. We don't have any coordinating ids for this. We could stash something on the form perhaps but given our current structure it's more difficult to get to the form instance in the commit phase and a naive solution wouldn't preserve ordering between forms. This solution isn't 100% guaranteed to preserve ordering between different React instances neither but should be in order within one instance which is the common case. The hard part is that we don't know what instance something will belong to until it hydrates. So to solve that I keep everything in the original queue while we wait, so that ordering is preserved until we know which instance it'll go into. I ended up doing a bunch of clever tricks to make this work. These could use a lot more tests than I have right now. Another thing that's tricky is that you can update the action before it's replayed but we actually want to invoke the old action if that happens. So we have to extract it even if we can't invoke it right now just so we get the one that was there during hydration.
bigfootjon
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Apr 18, 2024
We used to have Event Replaying for any kind of Discrete event where we'd track any event after hydrateRoot and before the async code/data has loaded in to hydrate the target. However, this didn't really work out because code inside event handlers are expected to be able to synchronously read the state of the world at the time they're invoked. If we replay discrete events later, the mutable state around them like selection or form state etc. may have changed. This limitation doesn't apply to Client Actions: - They're expected to be async functions that themselves work asynchronously. They're conceptually also in the "navigation" events that happen after the "submit" events so they're already not synchronously even before the first `await`. - They're expected to operate mostly on the FormData as input which we can snapshot at the time of the event. This PR adds a bit of inline script to the Fizz runtime (or external runtime) to track any early submit events on the page - but only if the action URL is our placeholder `javascript:` URL. We track a queue of these on `document.$$reactFormReplay`. Then we replay them in order as they get hydrated and we get a handle on the Client Action function. I add the runtime to the `bootstrapScripts` phase in Fizz which is really technically a little too late, because on a large page, it might take a while to get to that script even if you have displayed the form. However, that's also true for external runtime. So there's a very short window we might miss an event but it's good enough and better than risking blocking display on this script. The main thing that makes the replaying difficult to reason about is that we can have multiple instance of React using this same queue. This would be very usual but you could have two different Reacts SSR:ing different parts of the tree and using around the same version. We don't have any coordinating ids for this. We could stash something on the form perhaps but given our current structure it's more difficult to get to the form instance in the commit phase and a naive solution wouldn't preserve ordering between forms. This solution isn't 100% guaranteed to preserve ordering between different React instances neither but should be in order within one instance which is the common case. The hard part is that we don't know what instance something will belong to until it hydrates. So to solve that I keep everything in the original queue while we wait, so that ordering is preserved until we know which instance it'll go into. I ended up doing a bunch of clever tricks to make this work. These could use a lot more tests than I have right now. Another thing that's tricky is that you can update the action before it's replayed but we actually want to invoke the old action if that happens. So we have to extract it even if we can't invoke it right now just so we get the one that was there during hydration. DiffTrain build for commit bf449ee.
henriettelienrebnor
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Apr 23, 2025
<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"
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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"
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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
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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
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data-hovercard-url="/facebook/react/pull/25713/hovercard">#25713</a> by
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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
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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"
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data-hovercard-url="/facebook/react/pull/24580/hovercard">#24580</a> by
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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
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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
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href="https://redirect.github.com/sebmarkbage">@ sebmarkbage</a> and <a
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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
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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
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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
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href="https://redirect.github.com/acdlite">@ acdlite</a>)</li>
<li>Lazily propagate context changes (<a
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data-hovercard-type="pull_request"
data-hovercard-url="/facebook/react/pull/20890/hovercard">#20890</a> by
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href="https://redirect.github.com/acdlite">@ acdlite</a> and <a
class="user-mention notranslate" data-hovercard-type="user"
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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
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data-hovercard-url="/facebook/react/pull/25074/hovercard">#25074</a> by
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<li>Move update scheduling to microtask (<a
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<li>Consistently apply throttled retries (<a
href="https://redirect.github.com/facebook/…
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We used to have Event Replaying for any kind of Discrete event where we'd track any event after hydrateRoot and before the async code/data has loaded in to hydrate the target. However, this didn't really work out because code inside event handlers are expected to be able to synchronously read the state of the world at the time they're invoked. If we replay discrete events later, the mutable state around them like selection or form state etc. may have changed.
This limitation doesn't apply to Client Actions:
await.This PR adds a bit of inline script to the Fizz runtime (or external runtime) to track any early submit events on the page - but only if the action URL is our placeholder
javascript:URL. We track a queue of these ondocument.$$reactFormReplay. Then we replay them in order as they get hydrated and we get a handle on the Client Action function.I add the runtime to the
bootstrapScriptsphase in Fizz which is really technically a little too late, because on a large page, it might take a while to get to that script even if you have displayed the form. However, that's also true for external runtime. So there's a very short window we might miss an event but it's good enough and better than risking blocking display on this script.The main thing that makes the replaying difficult to reason about is that we can have multiple instance of React using this same queue. This would be very usual but you could have two different Reacts SSR:ing different parts of the tree and using around the same version. We don't have any coordinating ids for this. We could stash something on the form perhaps but given our current structure it's more difficult to get to the form instance in the commit phase and a naive solution wouldn't preserve ordering between forms.
This solution isn't 100% guaranteed to preserve ordering between different React instances neither but should be in order within one instance which is the common case.
The hard part is that we don't know what instance something will belong to until it hydrates. So to solve that I keep everything in the original queue while we wait, so that ordering is preserved until we know which instance it'll go into. I ended up doing a bunch of clever tricks to make this work. These could use a lot more tests than I have right now.
Another thing that's tricky is that you can update the action before it's replayed but we actually want to invoke the old action if that happens. So we have to extract it even if we can't invoke it right now just so we get the one that was there during hydration.