To recap. This only affects DEV and RSC. It patches console on the
server in DEV (similar to how React DevTools already does and what we
did for the double logging). Then replays those logs with a `[Server]`
badge on the client so you don't need a server terminal open.
This has been on for over 6 months now in our experimental channel and
we've had a lot of coverage in Next.js due to various experimental flags
like taint and ppr.
It's non-invasive in that even if something throws we just serialize
that as an unknown value.
The main feedback we've gotten was:
- The serialization depth wasn't deep enough which I addressed in #30294
and haven't really had any issues since. This could still be an issue or
the inverse that you serialize too many logs that are also too deep.
This is not so much an issue with intentional logging and things like
accidental errors don't typically have unbounded arguments (e.g. React
errors are always string arguments). The ideal would be some way to
retain objects and then load them on-demand but that needs more
plumbing. Which can be later.
- The other was that double logging on the server is annoying if the
same terminal does both the RSC render and SSR render which was
addressed in #30207. It is now off by default in node/edge-builds of the
client, on by default in browser builds. With the `replayConsole` option
to either opt-in or out.
We've reached a good spot now I think.
These are better with `enableOwnerStacks` but that's a separate track
and not needed.
The only thing to document here, other than maybe that we're doing it,
is the `replayConsole` option but that's part of the RSC renderers that
themselves are not documented so nowhere to document it.
enableHalt turns on a mode for flight prerenders where aborts are
treated like infinitely stalled outcomes while still completing the
prerender. For regular tasks we simply serialize the slot as a promise
that never settles. For ReadableStream, Blob, and Async Iterators we
just never advance the serialization so they remain unfinished when
consumed on the client.
When enableHalt is turned on aborts of prerenders will halt rather than
error. The abort reason is forwarded to the upstream produces of the
aforementioned async iterators, blobs, and ReadableStreams. In the
future if we expose a signal that you can consume from within a render
to cancel additional work the abort reason will also be forwarded there
Persistent renderers used the `Update` effect flag to check if a subtree
needs to be cloned. In some cases, that causes extra renders, such as
when a layout effect is triggered which only has an effect on the JS
side, but doesn't update the host components.
It's been a bit tricky to find the right places where this needs to be
set and I'm not 100% sure I got all the cases even though the tests
passed.
There is currently a mismatch in how the persistent mode JS API and the
Fabric native code interpret `completeRoot`.
This is a short-lived experiment to see the effect of moving the Fabric
`completeRoot` call from `finalizeContainerChildren` to
`replaceContainerChildren` which in some cases does not get called.
**This API is not intended to ship. This is a temporary unstable hook
for internal performance profiling.**
This PR exposes `unstable_useContextWithBailout`, which takes a compare
function in addition to Context. The comparison function is run to
determine if Context propagation and render should bail out earlier.
`unstable_useContextWithBailout` returns the full Context value, same as
`useContext`.
We can profile this API against `useContext` to better measure the cost
of Context value updates and gather more data around propagation and
render performance.
The bailout logic and test cases are based on
https://github.com/facebook/react/pull/20646
Additionally, this implementation allows multiple values to be compared
in one hook by returning a tuple to avoid requiring additional Context
consumer hooks.
Following https://github.com/facebook/react/pull/30436
Concurrent by default strategy has been unshipped. Here we clean up the
`allowConcurrentByDefault` path and related logic/tests.
For now, this keeps the `concurrentUpdatesByDefaultOverride` argument in
`createContainer` and `createHydrationContainer` and ignores the value
to prevent more breaking changes to `react-reconciler` in the RC stage.
Concurrent by default has been unshipped! Let's clean it up.
Here we remove `forceConcurrentByDefaultForTesting`, which allows us to
run tests against both concurrent strategies. In the next PR, we'll
remove the actual concurrent by default code path.
While the goal is to remove legacy context completely, I think we can
already land the removal of legacy context for function components. I
didn't even know this feature existed until reading the code recently.
The win is just a couple of property lookups on function renders, but it
trims down the API already as the full removal will likely still take a
bit more time.
www: Starting with enabled test renderer and a feature flag for
production rollout.
RN: Not enabled, will follow up on this.
Object literals should be faster at least on React Native with Hermes as
the JS engine.
It might also be interesting to confirm the old comments in this file
from years ago are even still valid. Creating an object from a literal
should be a simpler operation.
It's a bit unfortunate that this introduces a bunch of copied code, but
since we rearely update the fields on fibers, this seems like an okay
tradeoff for a hot code path. An alternative would be some sort of macro
system, but that doesn't seem worth the extra complexity.
## Summary
We currently do deep diffing for object props, and also use custom
differs, if they are defined, for props with custom attribute config.
The idea is to simply do a `===` comparison instead of all that work. We
will do less computation on the JS side, but send more data to native.
The hypothesis is that this change should be neutral in terms of
performance. If that's the case, we'll be able to get rid of custom
differs, and be one step closer to deleting view configs.
This PR adds the `enableShallowPropDiffing` feature flag to support this
experiment.
## How did you test this change?
With `enableShallowPropDiffing` hardcoded to `true`:
```
yarn test packages/react-native-renderer
```
This fails on the following test cases:
- should use the diff attribute
- should do deep diffs of Objects by default
- should skip deeply-nested changed functions
Which makes sense with this change. These test cases should be deleted
if the experiment is shipped.
`disableDOMTestUtils` and the FB build `ReactTestUtilsFB` allowed us to
finish migrating internal callsites off of ReactTestUtils. Now that
usage is cleaned up, we can remove the flag, build artifact, and test
coverage for the deprecated utility methods.
## Summary
The experiment has shown no significant performance changes. This PR
removes it.
## How did you test this change?
```
yarn flow native
yarn lint
```
This is the first step to experimenting with a new type of stack traces
behind the `enableOwnerStacks` flag - in DEV only.
The idea is to generate stacks that are more like if the JSX was a
direct call even though it's actually a lazy call. Not only can you see
which exact JSX call line number generated the erroring component but if
that's inside an abstraction function, which function called that
function and if it's a component, which component generated that
component. For this to make sense it really need to be the "owner" stack
rather than the parent stack like we do for other component stacks. On
one hand it has more precise information but on the other hand it also
loses context. For most types of problems the owner stack is the most
useful though since it tells you which component rendered this
component.
The problem with the platform in its current state is that there's two
ways to deal with stacks:
1) `new Error().stack`
2) `console.createTask()`
The nice thing about `new Error().stack` is that we can extract the
frames and piece them together in whatever way we want. That is great
for constructing custom UIs like error dialogs. Unfortunately, we can't
take custom stacks and set them in the native UIs like Chrome DevTools.
The nice thing about `console.createTask()` is that the resulting stacks
are natively integrated into the Chrome DevTools in the console and the
breakpoint debugger. They also automatically follow source mapping and
ignoreLists. The downside is that there's no way to extract the async
stack outside the native UI itself so this information cannot be used
for custom UIs like errors dialogs. It also means we can't collect this
on the server and then pass it to the client for server components.
The solution here is that we use both techniques and collect both an
`Error` object and a `Task` object for every JSX call.
The main concern about this approach is the performance so that's the
main thing to test. It's certainly too slow for production but it might
also be too slow even for DEV.
This first PR doesn't actually use the stacks yet. It just collects them
as the first step. The next step is to start utilizing this information
in error printing etc.
For RSC we pass the stack along across over the wire. This can be
concatenated on the client following the owner path to create an owner
stack leading back into the server. We'll later use this information to
restore fake frames on the client for native integration. Since this
information quickly gets pretty heavy if we include all frames, we strip
out the top frame. We also strip out everything below the functions that
call into user space in the Flight runtime. To do this we need to figure
out the frames that represents calling out into user space. The
resulting stack is typically just the one frame inside the owner
component's JSX callsite. I also eagerly strip out things we expect to
be ignoreList:ed anyway - such as `node_modules` and Node.js internals.
Following #28768, add a path to testing Fast JSX on www.
We want to measure the impact of Fast JSX and enable a path to testing
before string refs are completely removed in www (which is a work in
progress).
Without `disableStringRefs`, we need to copy any object with a `ref` key
so we can pass it through `coerceStringRef()` and copy it into the
object. This de-opt path is what is gated behind
`enableFastJSXWithStringRefs`.
The additional checks should have no perf impact in OSS as the flags
remain true there and the build output is not changed. For www, I've
benchmarked the addition of the boolean checks with values cached at
module scope. There is no significant change observed from our
benchmarks and any latency will apply to test and control branches
evenly. This added experiment complexity is temporary. We should be able
to clean it up, along with the flag checks for `enableRefAsProp` and
`disableStringRefs` shortly.
## Summary
This PR introduces a faster version of the `addProperties` function.
This new function is basically the `diffProperties` with `prevProps` set
to `null`, propagated constants, and all the unreachable code paths
collapsed.
## How did you test this change?
I've tested this change with [the benchmark
app](https://github.com/react-native-community/RNNewArchitectureApp/tree/new-architecture-benchmarks)
and got ~4.4% improvement in the view creation time.
This removes the automatic patching of the global `fetch` function in
Server Components environments to dedupe requests using `React.cache`, a
behavior that some RSC framework maintainers have objected to.
We may revisit this decision in the future, but for now it's not worth
the controversy.
Frameworks that have already shipped this behavior, like Next.js, can
reimplement it in userspace.
I considered keeping the implementation in the codebase and disabling it
by setting `enableFetchInstrumentation` to `false` everywhere, but since
that also disables the tests, it doesn't seem worth it because without
test coverage the behavior is likely to drift regardless. We can just
revert this PR later if desired.
Stacked on #28849, #28854, #28853. Behind a flag.
If you're following along from the side-lines. This is probably not what
you think it is.
It's NOT a way to get updates to a component over time. The
AsyncIterable works like an Iterable already works in React which is how
an Array works. I.e. it's a list of children - not the value of a child
over time.
It also doesn't actually render one component at a time. The way it
works is more like awaiting the entire list to become an array and then
it shows up. Before that it suspends the parent.
To actually get these to display one at a time, you have to opt-in with
`<SuspenseList>` to describe how they should appear. That's really the
interesting part and that not implemented yet.
Additionally, since these are effectively Async Functions and uncached
promises, they're not actually fully "supported" on the client yet for
the same reason rendering plain Promises and Async Functions aren't.
They warn. It's only really useful when paired with RSC that produces
instrumented versions of these. Ideally we'd published instrumented
helpers to help with map/filter style operations that yield new
instrumented AsyncIterables.
The way the implementation works basically just relies on unwrapThenable
and otherwise works like a plain Iterator.
There is one quirk with these that are different than just promises. We
ask for a new iterator each time we rerender. This means that upon retry
we kick off another iteration which itself might kick off new requests
that block iterating further. To solve this and make it actually
efficient enough to use on the client we'd need to stash something like
a buffer of the previous iteration and maybe iterator on the iterable so
that we can continue where we left off or synchronously iterate if we've
seen it before. Similar to our `.value` convention on Promises.
In Fizz, I had to do a special case because when we render an iterator
child we don't actually rerender the parent again like we do in Fiber.
However, it's more efficient to just continue on where we left off by
reusing the entries from the thenable state from before in that case.
We have changed the shape (and the runtime) of React Elements. To help
avoid precompiled or inlined JSX having subtle breakages or deopting
hidden classes, I renamed the symbol so that we can early error if
private implementation details are used or mismatching versions are
used.
Why "transitional"? Well, because this is not the last time we'll change
the shape. This is just a stepping stone to removing the `ref` field on
the elements in the next version so we'll likely have to do it again.
Adds an experimental feature flag to the implementation of useMemoCache,
the internal cache used by the React Compiler (Forget).
When enabled, instead of treating the cache as copy-on-write, like we do
with fibers, we share the same cache instance across all render
attempts, even if the component is interrupted before it commits.
If an update is interrupted, either because it suspended or because of
another update, we can reuse the memoized computations from the previous
attempt. We can do this because the React Compiler performs atomic
writes to the memo cache, i.e. it will not record the inputs to a
memoization without also recording its output.
This gives us a form of "resuming" within components and hooks.
This only works when updating a component that already mounted. It has
no impact during initial render, because the memo cache is stored on the
fiber, and since we have not implemented resuming for fibers, it's
always a fresh memo cache, anyway.
However, this alone is pretty useful — it happens whenever you update
the UI with fresh data after a mutation/action, which is extremely
common in a Suspense-driven (e.g. RSC or Relay) app.
So the impact of this feature is faster data mutations/actions (when the
React Compiler is used).
## Summary
This PR adds early return to the `diff` function. We don't need to go
through all the entries of `nextProps`, process and deep-diff the values
if `nextProps` is the same object as `prevProps`. Roughly 6% of all
`diffProperties` calls can be skipped.
## How did you test this change?
RNTester.
This adds support in Flight for serializing four kinds of streams:
- `ReadableStream` with objects as a model. This is a single shot
iterator so you can read it only once. It can contain any value
including Server Components. Chunks are encoded as is so if you send in
10 typed arrays, you get the same typed arrays out on the other side.
- Binary `ReadableStream` with `type: 'bytes'` option. This supports the
BYOB protocol. In this mode, the receiving side just gets `Uint8Array`s
and they can be split across any single byte boundary into arbitrary
chunks.
- `AsyncIterable` where the `AsyncIterator` function is different than
the `AsyncIterable` itself. In this case we assume that this might be a
multi-shot iterable and so we buffer its value and you can iterate it
multiple times on the other side. We support the `return` value as a
value in the single completion slot, but you can't pass values in
`next()`. If you want single-shot, return the AsyncIterator instead.
- `AsyncIterator`. These gets serialized as a single-shot as it's just
an iterator.
`AsyncIterable`/`AsyncIterator` yield Promises that are instrumented
with our `.status`/`.value` convention so that they can be synchronously
looped over if available. They are also lazily parsed upon read.
We can't do this with `ReadableStream` because we use the native
implementation of `ReadableStream` which owns the promises.
The format is a leading row that indicates which type of stream it is.
Then a new row with the same ID is emitted for every chunk. Followed by
either an error or close row.
`AsyncIterable`s can also be returned as children of Server Components
and then they're conceptually the same as fragment arrays/iterables.
They can't actually be used as children in Fizz/Fiber but there's a
separate plan for that. Only `AsyncIterable` not `AsyncIterator` will be
valid as children - just like sync `Iterable` is already supported but
single-shot `Iterator` is not. Notably, neither of these streams
represent updates over time to a value. They represent multiple values
in a list.
When the server stream is aborted we also close the underlying stream.
However, closing a stream on the client, doesn't close the underlying
stream.
A couple of possible follow ups I'm not planning on doing right now:
- [ ] Free memory by releasing the buffer if an Iterator has been
exhausted. Single shots could be optimized further to release individual
items as you go.
- [ ] We could clean up the underlying stream if the only pending data
that's still flowing is from streams and all the streams have cleaned
up. It's not very reliable though. It's better to do cancellation for
the whole stream - e.g. at the framework level.
- [ ] Implement smarter Binary Stream chunk handling. Currently we wait
until we've received a whole row for binary chunks and copy them into
consecutive memory. We need this to preserve semantics when passing
typed arrays. However, for binary streams we don't need that. We can
just send whatever pieces we have so far.
Per team discussion, this upgrades the `initialValue` argument for
`useDeferredValue` from experimental to canary.
- Original implementation PR:
https://github.com/facebook/react/pull/27500
- API documentation PR: https://github.com/reactjs/react.dev/pull/6747
I left it disabled at Meta for now in case there's old code somewhere
that is still passing an `options` object as the second argument.
This removes defaultProps support for all component types except for
classes. We've chosen to continue supporting defaultProps for classes
because lots of older code relies on it, and unlike function components,
(which can use default params), there's no straightforward alternative.
By implication, it also removes support for setting defaultProps on
`React.lazy` wrapper. So this will not work:
```js
const MyClassComponent = React.lazy(() => import('./MyClassComponent'));
// MyClassComponent is not actually a class; it's a lazy wrapper. So
// defaultProps does not work.
MyClassComponent.defaultProps = { foo: 'bar' };
```
However, if you set the default props on the class itself, then it's
fine.
For classes, this change also moves where defaultProps are resolved.
Previously, defaultProps were resolved by the JSX runtime. This change
is only observable if you introspect a JSX element, which is relatively
rare but does happen.
In other words, previously `<ClassWithDefaultProp />.props.aDefaultProp`
would resolve to the default prop value, but now it does not.
Cleanup enableUseRefAccessWarning flag
I don't think this flag has a path forward in the current
implementation. The detection by stack trace is too brittle to detect
the lazy initialization pattern reliably (see e.g. some internal tests
that expect the warning because they use lazy intialization, but a
slightly different pattern then the expected pattern.
I think a new version of this could be to fully ban ref access during
render with an alternative API for the exceptional cases that today
require ref access during render.
Only the FB entry point has legacy mode now so we can move the remaining
code in there.
Also enable disableLegacyMode in modern www builds since it doesn't
expose those entry points.
Now dependent on #28709.
---------
Co-authored-by: Josh Story <story@hey.com>
We've rolled out this flag internally on WWW. This PR removed flag
`enableCustomElementPropertySupport`
Test plan:
-- `yarn test`
Co-authored-by: Ricky Hanlon <rickhanlonii@gmail.com>
Remove module pattern function component support (flag only)
> This is a redo of #27742, but only including the flag removal,
excluding further simplifications.
The module pattern
```
function MyComponent() {
return {
render() {
return this.state.foo
}
}
}
```
has been deprecated for approximately 5 years now. This PR removes
support for this pattern.
This breaks internal tests, so must be something in the refactor. Since
it's the top commit let's revert and split into two PRs, one that
removes the flag and one that does the refactor, so we can find the bug.
The module pattern
```
function MyComponent() {
return {
render() {
return this.state.foo
}
}
}
```
has been deprecated for approximately 5 years now. This PR removes
support for this pattern. It also simplifies a number of code paths in
particular related to the concept of `IndeterminateComponent` types.
## Overview
This has landed, so we can remove the flag
## Changelog
This change blocks using javascript URLs such as:
```html
<a href="javascript:notfine">p0wned</a>
```
We previously announced dropping support for this via a warning:
> A future version of React will block javascript: URLs as a security
precaution. Use event handlers instead if you can. If you need to
generate unsafe HTML try using dangerouslySetInnerHTML instead.
If false, this ignores text comparison checks during hydration at the
risk of privacy safety.
Since React 18 we recreate the DOM starting from the nearest Suspense
boundary if any of the text content mismatches. This ensures that if we
have nodes that otherwise line up correctly such as if they're the same
type of Component but in a different order, then we don't accidentally
transfer state or attributes to the wrong one.
If we didn't do this e.g. attributes like image src might not line up
with the text. E.g. you might show the wrong profile picture with the
wrong name. However, the main reason we do this is because it's a
security/privacy concern if state from the original node can transfer to
the other one. For example if you start typing into a text field to
reply to a story but then it turns out that the hydration was in a
different order, you might submit that text into a different story than
you intended. Similarly, if you've already clicked an item and that gets
replayed using Action replaying or is synchronously force hydrated -
that click might end up applying to a different item in the list than
you intended. E.g. liking the wrong photo.
Unfortunately a common case where this happens is when Google Translate
is applied to a page. It'll always cause mismatches and recreate the
tree. Most of the time this wouldn't be visible to users because it'd
just recreate to the same thing and then translate again. It can affect
metrics that trace when this hydration happened though.
Meta can use this flag to decide if they favor this perf metric over the
risk to user privacy.
This is similar to the old enableClientRenderFallbackOnTextMismatch flag
except this flag doesn't patch up the text when there's a mismatch.
Because we don't have the patching anymore. The assumption is that it is
safe to ignore the safety concern because we assume it's a match and
therefore favoring not patching it will lead to better perf.
## Summary
Based on
- https://github.com/facebook/react/pull/27903
This PR
- Silence warning in React tests
- Turn on flag
We want to finish cleaning up internal RTR usage, but let's prioritize
the deprecation process. We do this by silencing the internal warning
for now.
## How did you test this change?
`yarn build`
`yarn test ReactHooksInspectionIntegration -b`
## Summary
After realizing that this feature flag is entangled with
`alwaysThrottleRetries`, we're going to undo
https://github.com/facebook/react/pull/28550
## How did you test this change?
```
$ yarn test
$ yarn flow dom-browser
$ yarn flow dom-fb
$ yarn flow fabric
```
## Summary
Creates a new `alwaysThrottleDisappearingFallbacks` feature flag that
gates the changes from https://github.com/facebook/react/pull/26802
(instead of being controlled by `alwaysThrottleRetries`). The values of
this new flag mirror the current values of `alwaysThrottleRetries` such
that there is no behavior difference.
This additional feature flag allows us to incrementally validate the
change (arguably bug fix) from
https://github.com/facebook/react/pull/26802 independently from
`alwaysThrottleRetries`.
## How did you test this change?
```
$ yarn test
$ yarn flow dom-browser
$ yarn flow dom-fb
$ yarn flow fabric
```
## Summary
We want to enable the new event loop in React Native
(https://github.com/react-native-community/discussions-and-proposals/pull/744)
for all users in the new architecture (determined by the use of
bridgeless, not by the use of Fabric). In order to leverage that, we
need to also set the flag for the React reconciler to use microtasks for
scheduling (so we'll execute them at the right time in the new event
loop).
This migrates from the previous approach using a dynamic flag (to be
used at Meta) with the check of a global set by React Native. The reason
for doing this is:
1) We still need to determine this dynamically in OSS (based on
Bridgeless, not on Fabric).
2) We still need the ability to configure the behavior at Meta, and for
internal build system reasons we cannot access the flag that enables
microtasks in
[`ReactNativeFeatureFlags`](6c28c87c4d/packages/react-native/src/private/featureflags/ReactNativeFeatureFlags.js (L121)).
## How did you test this change?
Manually synchronized the changes to React Native and ran all tests for
the new architecture on it. Also tested manually.
> [!NOTE]
> This change depends on
https://github.com/facebook/react-native/pull/43397 which has been
merged already
We broke the ability to "break on uncaught exceptions" by adding a
try/catch higher up in the scheduling. We're giving up on fixing that so
we can remove the replay trick inside an event handler.
The issue with that approach is that we end up double logging a lot of
errors in DEV since they get reported to the page.
It's also a lot of complexity around this feature.
## Summary
Looks like this was added years ago for instrumentation at meta that
never ended up rolling out. Should be safe to clean up.
## How did you test this change?
`yarn test`
Adds a flag to disable legacy mode. Currently this flag is used to cause
legacy mode apis like render and hydrate to throw. This change also
removes render, hydrate, unmountComponentAtNode, and
unstable_renderSubtreeIntoContainer from the experiemntal entrypoint.
Right now for Meta builds this flag is off (legacy mode is still
supported). In OSS builds this flag matches __NEXT_MAJOR__ which means
it currently is on in experiemental. This means that after merging
legacy mode is effectively removed from experimental builds. While this
is a breaking change, experimental builds are not stable and users can
pin to older versions or update their use of react-dom to no longer use
legacy mode APIs.
Depends on:
- https://github.com/facebook/react/pull/28398
---
This removes string refs, which has been deprecated in Strict Mode for
seven years.
I've left them behind a flag for Meta, but in open source this fully
removes the feature.
## Summary
Moving towards deprecation of ReactTestRenderer. Log a warning on each
render so we can remove the exports in a future major version.
We can enable this flag in web RTR without disrupting RN tests by
flipping the flag in
`packages/shared/forks/ReactFeatureFlags.test-renderer.js`
## How did you test this change?
`yarn test
packages/react-test-renderer/src/__tests__/ReactTestRenderer-test.js`
When developing in an RSC environment, you should be able to work in a
single environment as if it was a unified environment. With thrown
errors we already serialize them and then rethrow them on the client.
Since by default we log them via onError both in Flight and Fizz, you
can get the same log in the RSC runtime, the SSR runtime and on the
client.
With console logs made in SSR renders, you typically replay the same
code during hydration on the client. So for example warnings already
show up both in the SSR logs and on the client (although not guaranteed
to be the same). You could just spend your time in the client and you'd
be fine.
Previously, RSC logs would not be replayed because they don't hydrate.
So it's easy to miss warnings for example.
With this approach, we replay RSC logs both during SSR so they end up in
the SSR logs and on the client. That way you can just stay in the
browser window during normal development cycles. You shouldn't have to
care if your component is a server or client component when working on
logical things or iterating on a product.
With this change, you probably should mostly ignore the Flight log
stream and just look at the client or maybe the SSR one. Unless you're
digging into something specific. In particular if you just naively run
both Flight and Fizz in the same terminal you get duplicates. I like to
run out fixtures `yarn dev:region` and `yarn dev:global` in two separate
terminals.
Console logs may contain complex objects which can be inspected. Ideally
a DevTools inspector could reach into the RSC server and remotely
inspect objects using the remote inspection protocol. That way complex
objects can be loaded on demand as you expand into them. However, that
is a complex environment to set up and the server might not even be
alive anymore by the time you inspect the objects. Therefore, I do a
best effort to serialize the objects using the RSC protocol but limit
the depth that can be rendered.
This feature is only own in dev mode since it can be expensive.
In a follow up, I'll give the logs a special styling treatment to
clearly differentiate them from logs coming from the client. As well as
deal with stacks.
Depends on:
- #28317
- #28320
---
Changes the behavior of the JSX runtime to pass through `ref` as a
normal prop, rather than plucking it from the props object and storing
on the element.
This is a breaking change since it changes the type of the receiving
component. However, most code is unaffected since it's unlikely that a
component would have attempted to access a `ref` prop, since it was not
possible to get a reference to one.
`forwardRef` _will_ still pluck `ref` from the props object, though,
since it's extremely common for users to spread the props object onto
the inner component and pass `ref` as a differently named prop. This is
for maximum compatibility with existing code — the real impact of this
change is that `forwardRef` is no longer required.
Currently, refs are resolved during child reconciliation and stored on
the fiber. As a result of this change, we can move ref resolution to
happen only much later, and only for components that actually use them.
Then we can remove the `ref` field from the Fiber type. I have not yet
done that in this step, though.
Previously, `<Context>` was equivalent to `<Context.Consumer>`. However,
since the introduction of Hooks, the `<Context.Consumer>` API is rarely
used. The goal here is to make the common case cleaner:
```js
const ThemeContext = createContext('light')
function App() {
return (
<ThemeContext value="dark">
...
</ThemeContext>
)
}
function Button() {
const theme = use(ThemeContext)
// ...
}
```
This is technically a breaking change, but we've been warning about
rendering `<Context>` directly for several years by now, so it's
unlikely much code in the wild depends on the old behavior. [Proof that
it warns today (check
console).](https://codesandbox.io/p/sandbox/peaceful-nobel-pdxtfl)
---
**The relevant commit is 5696782b428a5ace96e66c1857e13249b6c07958.** It
switches `createContext` implementation so that `Context.Provider ===
Context`.
The main assumption that changed is that a Provider's fiber type is now
the context itself (rather than an intermediate object). Whereas a
Consumer's fiber type is now always an intermediate object (rather than
it being sometimes the context itself and sometimes an intermediate
object).
My methodology was to start with the relevant symbols, work tags, and
types, and work my way backwards to all usages.
This might break tooling that depends on inspecting React's internal
fields. I've added DevTools support in the second commit. This didn't
need explicit versioning—the structure tells us enough.
Turn this on
Edited: ope, nvm
<details>
Looks like there's still an outstanding issue with this. The original PR
turned off a strict effects test, which causes a stray
`componentWillUnmount` to fire.
5d1ce65139 (diff-19df471970763c4790c2cc0811fd2726cc6a891b0e1d5dedbf6d0599240c127aR70)
Before:
```js
expect(log).toEqual([
'constructor',
'constructor',
'getDerivedStateFromProps',
'getDerivedStateFromProps',
'render',
'render',
'componentDidMount',
]);
```
After:
```js
expect(log).toEqual([
'constructor',
'constructor',
'getDerivedStateFromProps',
'getDerivedStateFromProps',
'render',
'render',
'componentDidMount',
'componentWillUnmount',
'componentDidMount',
]);
```
So there's a bug somewhere
</details>
This is a partial redo of https://github.com/facebook/react/pull/26625.
Since that was unlanded due to some detected breakages. This now
includes a feature flag to be careful in rolling this out.
Adds a feature flag to control whether the client cache function is just
a passthrough. before we land breaking changes for the next major it
will be off and then we can flag it on when we want to break it.
flag is off for OSS for now and on elsewhere (though the parent flag
enableCache is off in some cases)
Server Context was never documented, and has been deprecated in
https://github.com/facebook/react/pull/27424.
This PR removes it completely, including the implementation code.
Notably, `useContext` is removed from the shared subset, so importing it
from a React Server environment would now should be a build error in
environments that are able to enforce that.
Conceptually a Server Component in the tree is the same as a Client
Component.
When we render a Server Component with a key, that key should be used as
part of the reconciliation process to ensure the children's state are
preserved when they move in a set. The key of a child should also be
used to clear the state of the children when that key changes.
Conversely, if a Server Component doesn't have a key it should get an
implicit key based on the slot number. It should not inherit the key of
its children since the children don't know if that would collide with
other keys in the set the Server Component is rendered in.
A Client Component also has an identity based on the function's
implementation type. That mainly has to do with the state (or future
state after a refactor) that Component might contain. To transfer state
between two implementations it needs to be of the same state type. This
is not a concern for a Server Components since they never have state so
identity doesn't matter.
A Component returns a set of children. If it returns a single child,
that's the same as returning a fragment of one child. So if you
conditionally return a single child or a fragment, they should
technically reconcile against each other.
The simple way to do this is to simply emit a Fragment for every Server
Component. That would be correct in all cases. Unfortunately that is
also unfortunate since it bloats the payload in the common cases. It
also means that Fiber creates an extra indirection in the runtime.
Ideally we want to fold Server Component aways into zero cost on the
client. At least where possible. The common cases are that you don't
specify a key on a single return child, and that you do specify a key on
a Server Component in a dynamic set.
The approach in this PR treats a Server Component that returns other
Server Components or Lazy Nodes as a sequence that can be folded away.
I.e. the parts that don't generate any output in the RSC payload.
Instead, it keeps track of their keys on an internal "context". Which
gets reset after each new reified JSON node gets rendered.
Then we transfer the accumulated keys from any parent Server Components
onto the child element. In the simple case, the child just inherits the
key of the parent.
If the Server Component itself is keyless but a child isn't, we have to
add a wrapper fragment to ensure that this fragment gets the implicit
key but we can still use the key to reset state. This is unusual though
because typically if you keyed something it's because it was already in
a fragment.
In the case a Server Component is keyed but forks its children using a
fragment, we need to key that fragment so that the whole set can move
around as one. In theory this could be flattened into a parent array but
that gets tricky if something suspends, because then we can't send the
siblings early.
The main downside of this approach is that switching between single
child and fragment in a Server Component isn't always going to reconcile
against each other. That's because if we saw a single child first, we'd
have to add the fragment preemptively in case it forks later. This
semantic of React isn't very well known anyway and it might be ok to
break it here for pragmatic reasons. The tests document this
discrepancy.
Another compromise of this approach is that when combining keys we don't
escape them fully. We instead just use a simple `,` separated concat.
This is probably good enough in practice. Additionally, since we don't
encode the implicit 0 index slot key, you can move things around between
parents which shouldn't really reconcile but does. This keeps the keys
shorter and more human readable.
There's no need to separate strict mode from strict effects mode any
more.
I didn't clean up the `StrictEffectMode` fiber flag, because it's used
to prevent strict effects in legacy mode. I could replace those checks
with `LegacyMode` checks, but when we remove legacy mode, we can remove
that flag and condense them into one StrictMode flag away.
This wires up the use of `async_hooks` in the Node build (as well as the
Edge build when a global is available) in DEV mode only. This will be
used to track debug info about what suspended during an RSC pass.
Enabled behind a flag for now.
It seems worthwhile to me to run a test to experiment with different
expiration times. This moves the expiration times for scheduler and
reconciler into FeatureFlags for the facebook build. Non-facebook should
not be affected by these changes.
An attempt to see if we can bring back expiration of retry lanes to
avoid cases resolving Suspense can be starved by frequent updates.
In the past, this caused increase browser crashes, but a lot of time has
passed since then. Just trying if we can re-enable this.
Old PR that reverted adding the timeout:
https://github.com/facebook/react/pull/21300
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## Summary
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does the pull request solve?
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The flag has been tested internally on WWW, should be good to set to
true for OSS. Added a dynamic flag for fb RN.
## How did you test this change?
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yarn test
Adds a second argument to useDeferredValue called initialValue:
```js
const value = useDeferredValue(finalValue, initialValue);
```
During the initial render of a component, useDeferredValue will return
initialValue. Once that render finishes, it will spawn an additional
render to switch to finalValue.
This same sequence should occur whenever the hook is hidden and revealed
again, i.e. by a Suspense or Activity, though this part is not yet
implemented.
When initialValue is not provided, useDeferredValue has no effect during
initial render, but during an update, it will remain on the previous
value, then spawn an additional render to switch to the new value. (This
is the same behavior that exists today.)
During SSR, initialValue is always used, if provided.
This feature is currently behind an experimental flag. We plan to ship
it in a non-breaking release.
## Summary
Currently when cloning nodes in Fabric, we reset a node's children on
each clone, and then repeatedly call appendChild to restore the previous
list of children (even if it was quasi-identical to before). This causes
unnecessary invalidation of the layout state in Fabric's ShadowNode data
(which in turn may require additional yoga clones) and extra JSI calls.
This PR adds a feature flag to pass in the children as part of the clone
call, so Fabric always has a complete view of the node that's being
mutated.
This feature flag requires matching changes in the react-native repo:
https://github.com/facebook/react-native/pull/39817
## How did you test this change?
Unit test added demonstrates the new behaviour
```
yarn test -r www-modern ReactFabric-test
yarn test ReactFabric-test.internal
```
Tested a manual sync into React Native and verified core surfaces render
correctly.
Upgrades the stability of Server Actions from experimental to canary.
- Turns on enableAsyncActions and enableFormActions
- Removes "experimental_" prefix from useOptimistic, useFormStatus, and
useFormState
This lets a registered object or value be "tainted", which we block from
crossing the serialization boundary. It's only allowed to stay
in-memory.
This is an extra layer of protection against mistakes of transferring
data from a data access layer to a client. It doesn't provide perfect
protection, because it doesn't trace through derived values and
substrings. So it shouldn't be used as the only security layer but more
layers are better.
`taintObjectReference` is for specific object instances, not any nested
objects or values inside that object. It's useful to avoid specific
objects from getting passed as is. It ensures that you don't
accidentally leak values in a specific context. It can be for security
reasons like tokens, privacy reasons like personal data or performance
reasons like avoiding passing large objects over the wire.
It might be privacy violation to leak the age of a specific user, but
the number itself isn't blocked in any other context. As soon as the
value is extracted and passed specifically without the object, it can
therefore leak.
`taintUniqueValue` is useful for high entropy values such as hashes,
tokens or crypto keys that are very unique values. In that case it can
be useful to taint the actual primitive values themselves. These can be
encoded as a string, bigint or typed array. We don't currently check for
this value in a substring or inside other typed arrays.
Since values can be created from different sources they don't just
follow garbage collection. In this case an additional object must be
provided that defines the life time of this value for how long it should
be blocked. It can be `globalThis` for essentially forever, but that
risks leaking memory for ever when you're dealing with dynamic values
like reading a token from a database. So in that case the idea is that
you pass the object that might end up in cache.
A request is the only thing that is expected to do any work. The
principle is that you can derive values from out of a tainted
entry during a request. Including stashing it in a per request cache.
What you can't do is store a derived value in a global module level
cache. At least not without also tainting the object.
## Summary
This is part of an effort to align the event loop in React Native with
its behavior on the Web. In this case, we're going to test enabling
microtasks in React Native (Fabric) and we need React to schedule work
using microtasks if available there. This just adds a feature flag to
configure that behavior at runtime.
## How did you test this change?
* Reviewed the generated code, which looks ok.
* Did a manual sync of this PR to Meta's internal infra and tested it
with my changes to enable microtasks in RN/Hermes.
This adds an experimental `unstable_postpone(reason)` API.
Currently we don't have a way to model effectively an Infinite Promise.
I.e. something that suspends but never resolves. The reason this is
useful is because you might have something else that unblocks it later.
E.g. by updating in place later, or by client rendering.
On the client this works to model as an Infinite Promise (in fact,
that's what this implementation does). However, in Fizz and Flight that
doesn't work because the stream needs to end at some point. We don't
have any way of knowing that we're suspended on infinite promises. It's
not enough to tag the promises because you could await those and thus
creating new promises. The only way we really have to signal this
through a series of indirections like async functions, is by throwing.
It's not 100% safe because these values can be caught but it's the best
we can do.
Effectively `postpone(reason)` behaves like a built-in [Catch
Boundary](https://github.com/facebook/react/pull/26854). It's like
`raise(Postpone, reason)` except it's built-in so it needs to be able to
be encoded and caught by Suspense boundaries.
In Flight and Fizz these behave pretty much the same as errors. Flight
just forwards it to retrigger on the client. In Fizz they just trigger
client rendering which itself might just postpone again or fill in the
value. The difference is how they get logged.
In Flight and Fizz they log to `onPostpone(reason)` instead of
`onError(error)`. This log is meant to help find deopts on the server
like finding places where you fall back to client rendering. The reason
that you pass in is for that purpose to help the reason for any deopts.
I do track the stack trace in DEV but I don't currently expose it to
`onPostpone`. This seems like a limitation. It might be better to expose
the Postpone object which is an Error object but that's more of an
implementation detail. I could also pass it as a second argument.
On the client after hydration they don't get passed to
`onRecoverableError`. There's no global `onPostpone` API to capture
postponed things on the client just like there's no `onError`. At that
point it's just assumed to be intentional. It doesn't have any `digest`
or reason passed to the client since it's not logged.
There are some hacky solutions that currently just tries to reuse as
much of the existing code as possible but should be more properly
implemented.
- Fiber is currently just converting it to a fake Promise object so that
it behaves like an infinite Promise.
- Fizz is encoding the magic digest string `"POSTPONE"` in the HTML so
we know to ignore it but it should probably just be something neater
that doesn't share namespace with digests.
Next I plan on using this in the `/static` entry points for additional
features.
Why "postpone"? It's basically a synonym to "defer" but we plan on using
"defer" for other purposes and it's overloaded anyway.
This uses the same mechanism as [large
strings](https://github.com/facebook/react/pull/26932) to encode chunks
of length based binary data in the RSC payload behind a flag.
I introduce a new BinaryChunk type that's specific to each stream and
ways to convert into it. That's because we sometimes need all chunks to
be Uint8Array for the output, even if the source is another array buffer
view, and sometimes we need to clone it before transferring.
Each type of typed array is its own row tag. This lets us ensure that
the instance is directly in the right format in the cached entry instead
of creating a wrapper at each reference. Ideally this is also how
Map/Set should work but those are lazy which complicates that approach a
bit.
We assume both server and client use little-endian for now. If we want
to support other modes, we'd convert it to/from little-endian so that
the transfer protocol is always little-endian. That way the common
clients can be the fastest possible.
So far this only implements Server to Client. Still need to implement
Client to Server for parity.
NOTE: This is the first time we make RSC effectively a binary format.
This is not compatible with existing SSR techniques which serialize the
stream as unicode in the HTML. To be compatible, those implementations
would have to use base64 or something like that. Which is what we'll do
when we move this technique to be built-in to Fizz.
## Summary
This PR cleans up `useMutableSource`. This has been blocked by a
remaining dependency internally at Meta, but that has now been deleted.
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## How did you test this change?
```
yarn flow
yarn lint
yarn test --prod
```
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## Summary
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We are upgrading React 17 codebase to React18, and `StrictMode` has been
great for surfacing potential production bugs on React18 for class
components. There are non-trivial number of test failures caused by
double `useEffect` in StrictMode. To prioritize surfacing and fixing
issues that will break in production now, we need a flag to turn off
double `useEffect` for now in StrictMode temporarily. This is a
Meta-only hack for rolling out `createRoot` and we will fast follow to
remove it and use full strict mode.
## How did you test this change?
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jest
## Overview
Does a few things:
- Renames `enableSyncDefaultUpdates` to
`forceConcurrentByDefaultForTesting`
- Changes the way it's used so it's dead-code eliminated separate from
`allowConcurrentByDefault`
- Deletes a bunch of the gated code
The gates that are deleted are unnecessary now. We were keeping them
when we originally thought we would come back to being concurrent by
default. But we've shifted and now sync-by default is the desired
behavior long term, so there's no need to keep all these forked tests
around.
I'll follow up to delete more of the forked behavior if possible.
Ideally we wouldn't need this flag even if we're still using
`allowConcurrentByDefault`.
This puts the change introduced by #26611 behind a flag until Meta is
able to roll it out. Disabling the flag reverts back to the old
behavior, where retries are throttled if there's still data remaining in
the tree, but not if all the data has finished loading.
The new behavior is still enabled in the public builds.
This lets you pass a function to `<form action={...}>` or `<button
formAction={...}>` or `<input type="submit formAction={...}>`. This will
behave basically like a `javascript:` URL except not quite implemented
that way. This is a convenience for the `onSubmit={e => {
e.preventDefault(); const fromData = new FormData(e.target); ... }`
pattern.
You can still implement a custom `onSubmit` handler and if it calls
`preventDefault`, it won't invoke the action, just like it would if you
used a full page form navigation or javascript urls. It behaves just
like a navigation and we might implement it with the Navigation API in
the future.
Currently this is just a synchronous function but in a follow up this
will accept async functions, handle pending states and handle errors.
This is implemented by setting `javascript:` URLs, but these only exist
to trigger an error message if something goes wrong instead of
navigating away. Like if you called `stopPropagation` to prevent React
from handling it or if you called `form.submit()` instead of
`form.requestSubmit()` which by-passes the `submit` event. If CSP is
used to ban `javascript:` urls, those will trigger errors when these
URLs are invoked which would be a different error message but it's still
there to notify the user that something went wrong in the plumbing.
Next up is improving the SSR state with action replaying and progressive
enhancement.
Implements initial (client-only) support for async actions behind a
flag. This is an experimental feature and the design isn't completely
finalized but we're getting closer. It will be layered alongside other
features we're working on, so it may not feel complete when considered
in isolation.
The basic description is you can pass an async function to
`startTransition` and all the transition updates that are scheduled
inside that async function will be grouped together. The `isPending`
flag will be set to true immediately, and only set back to false once
the async action has completed (as well as all the updates that it
triggers).
The ideal behavior would be that all updates spawned by the async action
are automatically inferred and grouped together; however, doing this
properly requires the upcoming (stage 2) Async Context API, which is not
yet implemented by browsers. In the meantime, we will fake this by
grouping together all transition updates that occur until the async
function has terminated. This can lead to overgrouping between unrelated
actions, which is not wrong per se, just not ideal.
If the `useTransition` hook is removed from the UI before an async
action has completed — for example, if the user navigates to a new page
— subsequent transitions will no longer be grouped with together with
that action.
Another consequence of the lack of Async Context is that if you call
`setState` inside an action but after an `await`, it must be wrapped in
`startTransition` in order to be grouped properly. If we didn't require
this, then there would be no way to distinguish action updates from
urgent updates caused by user input, too. This is an unfortunate footgun
but we can likely detect the most common mistakes using a lint rule.
Once Async Context lands in browsers, we can start warning in dev if we
detect an update that hasn't been wrapped in `startTransition`. Then,
longer term, once the feature is ubiquitous, we can rely on it for real
and allow you to call `setState` without the additional wrapper.
Things that are _not_ yet implemented in this PR, but will be added as
follow ups:
- Support for non-hook form of `startTransition`
- Canceling the async action scope if the `useTransition` hook is
deleted from the UI
- Anything related to server actions
