[Fizz] Support Suspense boundaries anywhere #32069
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| @@ -13,7 +13,7 @@ | |||
| // Use __VARIANT__ to simulate a GK. The tests will be run twice: once | |||
| // with the __VARIANT__ set to `true`, and once set to `false`. | |||
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| export const alwaysThrottleRetries = true; | |||
| export const alwaysThrottleRetries = __VARIANT__; | |||
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no I mistakenly reset this while debugging a different variant bug failing a test that was actually a problem in the test itself
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| if ( | ||
| request.pendingRootTasks === 0 && | ||
| request.trackedPostpones === null && | ||
| boundary.contentPreamble |
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Nit. boundary.contentPreamble !== null. Helps catch bugs when the types are not expected.
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| if ( | ||
| request.pendingRootTasks === 0 && | ||
| request.trackedPostpones === null && | ||
| boundary.contentPreamble |
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Jan 17, 2025
Suspense is meant to be composable but there has been a lonstanding limitation with using Suspense above the `<body>` tag of an HTML document due to peculiarities of how HTML is parsed. For instance if you used Suspense to render an entire HTML document and had a fallback that might flush an alternate Document the comment nodes which describe this boundary scope won't be where they need to be in the DOM for client React to properly hydrate them. This is somewhat a problem of our own making in that we have a concept of a Preamble and we leave the closing body and html tags behind until streaming has completed which produces a valid HTML document that also matches the DOM structure that would be parsed from it. However Preambles as a concept are too important to features like Float to imagine moving away from this model and so we can either choose to just accept that you cannot use Suspense anywhere except inside the `<body>` or we can build special support for Suspense into react-dom that has a coherent semantic with how HTML documents are written and parsed. This change implements Suspense support for react-dom/server by correctly serializing boundaries during rendering, prerendering, and resumgin on the server. It does not yet support Suspense everywhere on the client but this will arrive in a subsequent change. In practice Suspense cannot be used above the <body> tag today so this is not a breaking change since no programs in the wild could be using this feature anyway. React's streaming rendering of HTML doesn't lend itself to replacing the contents of the documentElement, head, or body of a Document. These are already special cased in fiber as HostSingletons and similarly for Fizz the values we render for these tags must never be updated by the Fizz runtime once written. To accomplish these we redefine the Preamble as the tags that represent these three singletons plus the contents of the document.head. If you use Suspense above any part of the Preamble then nothing will be written to the destination until the boundary is no longer pending. If the boundary completes then the preamble from within that boudnary will be output. If the boundary postpones or errors then the preamble from the fallback will be used instead. Additionally, by default anything that is not part of the preamble is implicitly in body scope. This leads to the somewhat counterintuitive consequence that the comment nodes we use to mark the borders of a Suspense boundary in Fizz can appear INSIDE the preamble that was rendered within it. Later when I update Fiber to support Suspense anywhere hydration will similarly start implicitly in the document body when the root is part of the preamble (the document or one of it's singletons).
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Suspense is meant to be composable but there has been a lonstanding
limitation with using Suspense above the `<body>` tag of an HTML
document due to peculiarities of how HTML is parsed. For instance if you
used Suspense to render an entire HTML document and had a fallback that
might flush an alternate Document the comment nodes which describe this
boundary scope won't be where they need to be in the DOM for client
React to properly hydrate them. This is somewhat a problem of our own
making in that we have a concept of a Preamble and we leave the closing
body and html tags behind until streaming has completed which produces a
valid HTML document that also matches the DOM structure that would be
parsed from it. However Preambles as a concept are too important to
features like Float to imagine moving away from this model and so we can
either choose to just accept that you cannot use Suspense anywhere
except inside the `<body>` or we can build special support for Suspense
into react-dom that has a coherent semantic with how HTML documents are
written and parsed.
This change implements Suspense support for react-dom/server by
correctly serializing boundaries during rendering, prerendering, and
resumgin on the server. It does not yet support Suspense everywhere on
the client but this will arrive in a subsequent change. In practice
Suspense cannot be used above the `<body>` tag today so this is not a
breaking change since no programs in the wild could be using this
feature anyway.
React's streaming rendering of HTML doesn't lend itself to replacing the
contents of the documentElement, head, or body of a Document. These are
already special cased in fiber as HostSingletons and similarly for Fizz
the values we render for these tags must never be updated by the Fizz
runtime once written. To accomplish these we redefine the Preamble as
the tags that represent these three singletons plus the contents of the
document.head. If you use Suspense above any part of the Preamble then
nothing will be written to the destination until the boundary is no
longer pending. If the boundary completes then the preamble from within
that boudnary will be output. If the boundary postpones or errors then
the preamble from the fallback will be used instead.
Additionally, by default anything that is not part of the preamble is
implicitly in body scope. This leads to the somewhat counterintuitive
consequence that the comment nodes we use to mark the borders of a
Suspense boundary in Fizz can appear INSIDE the preamble that was
rendered within it.
```typescript
render((
<Suspense>
<html lang="en">
<body>
<div>hello world</div>
</body>
</html>
</Suspense>
))
```
will produce an HTML document like this
```html
<!DOCTYPE html>
<html lang="en">
<head></head>
<body>
<!--$--> <-- this is the comment Node representing the outermost Suspense
<div>hello world</div>
<$--/$-->
</body>
</html>
```
Later when I update Fiber to support Suspense anywhere hydration will
similarly start implicitly in the document body when the root is part of
the preamble (the document or one of it's singletons).
DiffTrain build for [b25bcd4](b25bcd4)
This was referenced Jan 20, 2025
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback <html>, <head>, and <body> tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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…32163) This is a follow up to #32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback html, head, and body tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration)
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…32163) This is a follow up to #32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback html, head, and body tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration) DiffTrain build for [c492f97](c492f97)
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…32163) This is a follow up to #32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback html, head, and body tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration) DiffTrain build for [c492f97](c492f97)
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…acebook#32163) This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback html, head, and body tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration) DiffTrain build for [c492f97](facebook@c492f97)
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…acebook#32163) This is a follow up to facebook#32069 In the prior change I updated Fizz to allow you to render Suspense boundaries at any level within a react-dom application by treating the document body as the default render scope. This change updates Fiber to provide similar semantics. Note that this update still does not deliver hydration so unifying the Fizz and Fiber implementations in a single App is not possible yet. The implementation required a rework of the getHostSibling and getHostParent algorithms. Now most HostSingletons are invisible from a host positioning perspective. Head is special in that it is a valid host scope so when you have Placements inside of it, it will act as the parent. But body, and html, will not directly participate in host positioning. Additionally to support flipping to a fallback html, head, and body tag in a Suspense fallback I updated the offscreen hiding/unhide logic to pierce through singletons when lookin for matching hidable nod boundaries anywhere (excluding hydration) DiffTrain build for [c492f97](facebook@c492f97)
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…, html tag, or body tag (#32252) followup to * #32069 * #32163 * #32224 in react-dom in Dev we validate that the tag nesting is valid. This is motivated primarily because while browsers are tolerant to poor HTML there are many cases that if server rendered will be hydrated in a way that will break hydration. With the changes to singleton scoping where the document body is now the implicit render/hydration context for arbitrary tags at the root we need to adjust the validation logic to allow for valid programs such as rendering divs as a child of a Document (since this div will actually insert into the body).
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…, html tag, or body tag (#32252) followup to * #32069 * #32163 * #32224 in react-dom in Dev we validate that the tag nesting is valid. This is motivated primarily because while browsers are tolerant to poor HTML there are many cases that if server rendered will be hydrated in a way that will break hydration. With the changes to singleton scoping where the document body is now the implicit render/hydration context for arbitrary tags at the root we need to adjust the validation logic to allow for valid programs such as rendering divs as a child of a Document (since this div will actually insert into the body). DiffTrain build for [a0fdb63](a0fdb63)
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…, html tag, or body tag (#32252) followup to * #32069 * #32163 * #32224 in react-dom in Dev we validate that the tag nesting is valid. This is motivated primarily because while browsers are tolerant to poor HTML there are many cases that if server rendered will be hydrated in a way that will break hydration. With the changes to singleton scoping where the document body is now the implicit render/hydration context for arbitrary tags at the root we need to adjust the validation logic to allow for valid programs such as rendering divs as a child of a Document (since this div will actually insert into the body). DiffTrain build for [a0fdb63](a0fdb63)
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…, html tag, or body tag (facebook#32252) followup to * facebook#32069 * facebook#32163 * facebook#32224 in react-dom in Dev we validate that the tag nesting is valid. This is motivated primarily because while browsers are tolerant to poor HTML there are many cases that if server rendered will be hydrated in a way that will break hydration. With the changes to singleton scoping where the document body is now the implicit render/hydration context for arbitrary tags at the root we need to adjust the validation logic to allow for valid programs such as rendering divs as a child of a Document (since this div will actually insert into the body). DiffTrain build for [a0fdb63](facebook@a0fdb63)
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…, html tag, or body tag (facebook#32252) followup to * facebook#32069 * facebook#32163 * facebook#32224 in react-dom in Dev we validate that the tag nesting is valid. This is motivated primarily because while browsers are tolerant to poor HTML there are many cases that if server rendered will be hydrated in a way that will break hydration. With the changes to singleton scoping where the document body is now the implicit render/hydration context for arbitrary tags at the root we need to adjust the validation logic to allow for valid programs such as rendering divs as a child of a Document (since this div will actually insert into the body). DiffTrain build for [a0fdb63](facebook@a0fdb63)
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<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>
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<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>
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<b>19.1.0-canary-ef979d47-20241218</b> - 2024-12-18
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<b>19.1.0-canary-ef4bc8b4-20250328</b> - 2025-03-28
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<b>19.1.0-canary-ebc22ef7-20250225</b> - 2025-02-26
</li>
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<b>19.1.0-canary-e670e72f-20250214</b> - 2025-02-14
</li>
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<b>19.1.0-canary-e1e74071-20250321</b> - 2025-03-21
</li>
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<b>19.1.0-canary-e06c72fc-20241215</b> - 2024-12-16
</li>
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<b>19.1.0-canary-e03ac20f-20250305</b> - 2025-03-05
</li>
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<b>19.1.0-canary-de82912e-20241220</b> - 2024-12-20
</li>
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<b>19.1.0-canary-de1eaa26-20250124</b> - 2025-01-24
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<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/…
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Suspense is meant to be composable but there has been a lonstanding limitation with using Suspense above the
<body>tag of an HTML document due to peculiarities of how HTML is parsed. For instance if you used Suspense to render an entire HTML document and had a fallback that might flush an alternate Document the comment nodes which describe this boundary scope won't be where they need to be in the DOM for client React to properly hydrate them. This is somewhat a problem of our own making in that we have a concept of a Preamble and we leave the closing body and html tags behind until streaming has completed which produces a valid HTML document that also matches the DOM structure that would be parsed from it. However Preambles as a concept are too important to features like Float to imagine moving away from this model and so we can either choose to just accept that you cannot use Suspense anywhere except inside the<body>or we can build special support for Suspense into react-dom that has a coherent semantic with how HTML documents are written and parsed.This change implements Suspense support for react-dom/server by correctly serializing boundaries during rendering, prerendering, and resumgin on the server. It does not yet support Suspense everywhere on the client but this will arrive in a subsequent change. In practice Suspense cannot be used above the
<body>tag today so this is not a breaking change since no programs in the wild could be using this feature anyway.React's streaming rendering of HTML doesn't lend itself to replacing the contents of the documentElement, head, or body of a Document. These are already special cased in fiber as HostSingletons and similarly for Fizz the values we render for these tags must never be updated by the Fizz runtime once written. To accomplish these we redefine the Preamble as the tags that represent these three singletons plus the contents of the document.head. If you use Suspense above any part of the Preamble then nothing will be written to the destination until the boundary is no longer pending. If the boundary completes then the preamble from within that boudnary will be output. If the boundary postpones or errors then the preamble from the fallback will be used instead.
Additionally, by default anything that is not part of the preamble is implicitly in body scope. This leads to the somewhat counterintuitive consequence that the comment nodes we use to mark the borders of a Suspense boundary in Fizz can appear INSIDE the preamble that was rendered within it.
will produce an HTML document like this
Later when I update Fiber to support Suspense anywhere hydration will similarly start implicitly in the document body when the root is part of the preamble (the document or one of it's singletons).