This reverts commit b2ae9ddb3b.
While the feature flag is fully rolled out, these tests are also testing
behavior set with an unstable flag on root, which for now we want to
preserve.
Not sure if there's a better way then adding a dynamic feature flag to
the www build?
When React receives new input (via `setState`, a Suspense promise
resolution, and so on), it needs to ensure there's a rendering task
associated with the update. Most of this happens
`ensureRootIsScheduled`.
If a single event contains multiple updates, we end up running the
scheduling code once per update. But this is wasteful because we really
only need to run it once, at the end of the event (or in the case of
flushSync, at the end of the scope function's execution).
So this PR moves the scheduling logic to happen in a microtask instead.
In some cases, we will force it run earlier than that, like for
`flushSync`, but since updates are batched by default, it will almost
always happen in the microtask. Even for discrete updates.
In production, this should have no observable behavior difference. In a
testing environment that uses `act`, this should also not have a
behavior difference because React will push these tasks to an internal
`act` queue.
However, tests that do not use `act` and do not simulate an actual
production environment (like an e2e test) may be affected. For example,
before this change, if a test were to call `setState` outside of `act`
and then immediately call `jest.runAllTimers()`, the update would be
synchronously applied. After this change, that will no longer work
because the rendering task (a timer, in this case) isn't scheduled until
after the microtask queue has run.
I don't expect this to be an issue in practice because most people do
not write their tests this way. They either use `act`, or they write
e2e-style tests.
The biggest exception has been... our own internal test suite. Until
recently, many of our tests were written in a way that accidentally
relied on the updates being scheduled synchronously. Over the past few
weeks, @tyao1 and I have gradually converted the test suite to use a new
set of testing helpers that are resilient to this implementation detail.
(There are also some old Relay tests that were written in the style of
React's internal test suite. Those will need to be fixed, too.)
The larger motivation behind this change, aside from a minor performance
improvement, is we intend to use this new microtask to perform
additional logic that doesn't yet exist. Like inferring the priority of
a custom event.
This flag is already enabled everywhere except for www, which is blocked
by a few tests that assert on the old behavior. Once www is ready, I'll
land this.
This is a change to some undefined behavior that we though we would do
at one point but decided not to roll out. It's already disabled
everywhere, so this just deletes the branch from the implementation and
the tests.
Today if something suspends, React will continue rendering the siblings
of that component.
Our original rationale for prerendering the siblings of a suspended
component was to initiate any lazy fetches that they might contain. This
was when we were more bullish about lazy fetching being a good idea some
of the time (when combined with prefetching), as opposed to our latest
thinking, which is that it's almost always a bad idea.
Another rationale for the original behavior was that the render was I/O
bound, anyway, so we might as do some extra work in the meantime. But
this was before we had the concept of instant loading states: when
navigating to a new screen, it's better to show a loading state as soon
as you can (often a skeleton UI), rather than delay the transition.
(There are still cases where we block the render, when a suitable
loading state is not available; it's just not _all_ cases where
something suspends.) So the biggest issue with our existing
implementation is that the prerendering of the siblings happens within
the same render pass as the one that suspended — _before_ the loading
state appears.
What we should do instead is immediately unwind the stack as soon as
something suspends, to unblock the loading state.
If we want to preserve the ability to prerender the siblings, what we
could do is schedule special render pass immediately after the fallback
is displayed. This is likely what we'll do in the future. However, in
the new implementation of `use`, there's another reason we don't
prerender siblings: so we can preserve the state of the stack when
something suspends, and resume where we left of when the promise
resolves without replaying the parents. The only way to do this
currently is to suspend the entire work loop. Fiber does not currently
support rendering multiple siblings in "parallel". Once you move onto
the next sibling, the stack of the previous sibling is discarded and
cannot be restored. We do plan to implement this feature, but it will
require a not-insignificant refactor.
Given that lazy data fetching is already bad for performance, the best
trade off for now seems to be to disable prerendering of siblings. This
gives us the best performance characteristics when you're following best
practices (i.e. hoist data fetches to Server Components or route
loaders), at the expense of making an already bad pattern a bit worse.
Later, when we implement resumable context stacks, we can reenable
sibling prerendering. Though even then the use case will mostly be to
prerender the CPU-bound work, not lazy fetches.
The old version of prettier we were using didn't support the Flow syntax
to access properties in a type using `SomeType['prop']`. This updates
`prettier` and `rollup-plugin-prettier` to the latest versions.
I added the prettier config `arrowParens: "avoid"` to reduce the diff
size as the default has changed in Prettier 2.0. The largest amount of
changes comes from function expressions now having a space. This doesn't
have an option to preserve the old behavior, so we have to update this.
I noticed this was an experiment concluded 16 months ago (#21679) that
this extra work is beneficial
to break up cycles leaking memory in product code.
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This is the other approach for unifying default and sync lane
https://github.com/facebook/react/pull/25524.
The approach in that PR is to merge default and continuous lane into the
sync lane, and use a new field to track the priority. But there are a
couple places that field will be needed, and it is difficult to
correctly reset the field when there is no sync lane.
In this PR we take the other approach that doesn't remove any lane, but
batch them to get the behavior we want.
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yarn test
Co-authored-by: Andrew Clark <hi@andrewclark.io>
We originally had grand plans for using this Event concept for more but
now it's only meant to be used in combination with effects.
It's an Event in the FRP terms, that is triggered from an Effect.
Technically it can also be from another function that itself is
triggered from an existing side-effect but that's kind of an advanced
case.
The canonical case is an effect that triggers an event:
```js
const onHappened = useEffectEvent(() => ...);
useEffect(() => {
onHappened();
}, []);
```
We've heard from multiple contributors that the Reconciler forking
mechanism was confusing and/or annoying to deal with. Since it's
currently unused and there's no immediate plans to start using it again,
this removes the forking.
Fully removing the fork is split into 2 steps to preserve file history:
**This PR**
- remove `enableNewReconciler` feature flag.
- remove `unstable_isNewReconciler` export
- remove eslint rules for cross fork imports
- remove `*.new.js` files and update imports
- merge non-suffixed files into `*.old` files where both exist
(sometimes types were defined there)
**#25775**
- rename `*.old` files
This improves the error message a bit and ensures that we recommend
putting the key first, not last, which ensures that the faster
`jsx-runtime` is used.
This only affects the modern "automatic" JSX transform.
* Add fetch instrumentation in cached contexts
* Avoid unhandled rejection errors for Promises that we intentionally ignore
In the final passes, we ignore the newly generated Promises and use
the previous ones. This ensures that if those generate errors, that we
intentionally ignore those.
* Add extra fetch properties if there were any
* Facebook -> Meta in copyright
rg --files | xargs sed -i 's#Copyright (c) Facebook, Inc. and its affiliates.#Copyright (c) Meta Platforms, Inc. and affiliates.#g'
* Manual tweaks
This commit adds a new hook `useEvent` per the RFC [here](https://github.com/reactjs/rfcs/pull/220), gated as experimental.
Co-authored-by: Rick Hanlon <rickhanlonii@gmail.com>
Co-authored-by: Rick Hanlon <rickhanlonii@fb.com>
Co-authored-by: Lauren Tan <poteto@users.noreply.github.com>
* Internal `act`: Unwrapping resolved promises
This update our internal implementation of `act` to support React's new
behavior for unwrapping promises. Like we did with Scheduler, when
something suspends, it will yield to the main thread so the microtasks
can run, then continue in a new task.
I need to implement the same behavior in the public version of `act`,
but there are some additional considerations so I'll do that in a
separate commit.
* Move throwException to after work loop resumes
throwException is the function that finds the nearest boundary and
schedules it for a second render pass. We should only call it right
before we unwind the stack — not if we receive an immediate ping and
render the fiber again.
This was an oversight in 8ef3a7c that I didn't notice because it happens
to mostly work, anyway. What made me notice the mistake is that
throwException also marks the entire render phase as suspended
(RootDidSuspend or RootDidSuspendWithDelay), which is only supposed to
be happen if we show a fallback. One consequence was that, in the
RootDidSuspendWithDelay case, the entire commit phase was blocked,
because that's the exit status we use to block a bad fallback
from appearing.
* Use expando to check whether promise has resolved
Add a `status` expando to a thrown thenable to track when its value has
resolved.
In a later step, we'll also use `value` and `reason` expandos to track
the resolved value.
This is not part of the official JavaScript spec — think of
it as an extension of the Promise API, or a custom interface that is a
superset of Thenable. However, it's inspired by the terminology used
by `Promise.allSettled`.
The intent is that this will be a public API — Suspense implementations
can set these expandos to allow React to unwrap the value synchronously
without waiting a microtask.
* Scaffolding for `experimental_use` hook
Sets up a new experimental hook behind a feature flag, but does not
implement it yet.
* use(promise)
Adds experimental support to Fiber for unwrapping the value of a promise
inside a component. It is not yet implemented for Server Components,
but that is planned.
If promise has already resolved, the value can be unwrapped
"immediately" without showing a fallback. The trick we use to implement
this is to yield to the main thread (literally suspending the work
loop), wait for the microtask queue to drain, then check if the promise
resolved in the meantime. If so, we can resume the last attempted fiber
without unwinding the stack. This functionality was implemented in
previous commits.
Another feature is that the promises do not need to be cached between
attempts. Because we assume idempotent execution of components, React
will track the promises that were used during the previous attempt and
reuse the result. You shouldn't rely on this property, but during
initial render it mostly just works. Updates are trickier, though,
because if you used an uncached promise, we have no way of knowing
whether the underlying data has changed, so we have to unwrap the
promise every time. It will still work, but it's inefficient and can
lead to unnecessary fallbacks if it happens during a discrete update.
When we implement this for Server Components, this will be less of an
issue because there are no updates in that environment. However, it's
still better for performance to cache data requests, so the same
principles largely apply.
The intention is that this will eventually be the only supported way to
suspend on arbitrary promises. Throwing a promise directly will
be deprecated.
Implement basic support for "Resources". In the context of this commit, the only thing that is currently a Resource are
<link rel="stylesheet" precedence="some-value" ...>
Resources can be rendered anywhere in the react tree, even outside of normal parenting rules, for instance you can render a resource before you have rendered the <html><head> tags for your application. In the stream we reorder this so the browser always receives valid HTML and resources are emitted either in place (normal circumstances) or at the top of the <head> (when you render them above or before the <head> in your react tree)
On the client, resources opt into an entirely different hydration path. Instead of matching the location within the Document these resources are queried for in the entire document. It is an error to have more than one resource with the same href attribute.
The use of precedence here as an opt-in signal for resourcifying the link is in preparation for a more complete Resource implementation which will dedupe resource references (multiple will be valid), hoist to the appropriate container (body, head, or elsewhere), order (according to precedence) and Suspend boundaries that depend on them. More details will come in the coming weeks on this plan.
This feature is gated by an experimental flag and will only be made available in experimental builds until some future time.
This reverts commit 327e4a1f96.
Turns out we hadn't rolled this out internally yet — I mistook
enableClientRenderFallbackOnHydrationMismatch for
said enableClientRenderFallbackOnTextMismatch. Need to revert
until we finish rolling out the change.
* Flight side of server context
* 1 more test
* rm unused function
* flow+prettier
* flow again =)
* duplicate ReactServerContext across packages
* store default value when lazily initializing server context
* .
* better comment
* derp... missing import
* rm optional chaining
* missed feature flag
* React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED ??
* add warning if non ServerContext passed into useServerContext
* pass context in as array of arrays
* make importServerContext nott pollute the global context state
* merge main
* remove useServerContext
* dont rely on object getters in ReactServerContext and disallow JSX
* add symbols to devtools + rename globalServerContextRegistry to just ContextRegistry
* gate test case as experimental
* feedback
* remove unions
* Lint
* fix oopsies (tests/lint/mismatching arguments/signatures
* lint again
* replace-fork
* remove extraneous change
* rebase
* 1 more test
* rm unused function
* flow+prettier
* flow again =)
* duplicate ReactServerContext across packages
* store default value when lazily initializing server context
* .
* better comment
* derp... missing import
* rm optional chaining
* missed feature flag
* React.__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED ??
* add warning if non ServerContext passed into useServerContext
* pass context in as array of arrays
* make importServerContext nott pollute the global context state
* merge main
* remove useServerContext
* dont rely on object getters in ReactServerContext and disallow JSX
* add symbols to devtools + rename globalServerContextRegistry to just ContextRegistry
* gate test case as experimental
* feedback
* remove unions
* Lint
* fix oopsies (tests/lint/mismatching arguments/signatures
* lint again
* replace-fork
* remove extraneous change
* rebase
* reinline
* rebase
* add back changes lost due to rebase being hard
* emit chunk for provider
* remove case for React provider type
* update type for SomeChunk
* enable flag with experimental
* add missing types
* fix flow type
* missing type
* t: any
* revert extraneous type change
* better type
* better type
* feedback
* change import to type import
* test?
* test?
* remove react-dom
* remove react-native-renderer from react-server-native-relay/package.json
* gate change in FiberNewContext, getComponentNameFromType, use switch statement in FlightServer
* getComponentNameFromTpe: server context type gated and use displayName if available
* fallthrough
* lint....
* POP
* lint
Jan Kassens