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:
**#25774 previous PR that did the bulk of the work:**
- 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)
**This PR**
- rename `*.old` files
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
### Changes made:
- Running with enableFizzExternalRuntime (feature flag) and
unstable_externalRuntimeSrc (param) will generate html nodes with data
attributes that encode Fizz instructions.
```
<div
hidden data-rxi=""
data-bid="param0"
data-dgst="param1"
></div>
```
- Added an external runtime browser script
`ReactDOMServerExternalRuntime`, which processes and removes these nodes
- This runtime should be passed as to renderInto[...] via
`unstable_externalRuntimeSrc`
- Since this runtime is render blocking (for all streamed suspense
boundaries and segments), we want this to reach the client as early as
possible. By default, Fizz will send this script at the end of the shell
when it detects dynamic content (e.g. suspenseful pending tasks), but it
can be sent even earlier by calling `preinit(...)` inside a component.
- The current implementation relies on Float to dedupe sending
`unstable_externalRuntimeSrc`, so `enableFizzExternalRuntime` is only
valid when `enableFloat` is also set.
Add option for ref function to return a clean up function.
```jsx
<div ref={(_ref) => {
// Use `_ref`
return () => {
// Clean up _ref
};
}} />
```
If clean up function is not provided. Ref function is called with null
like it has been before.
```jsx
<div ref={(_ref) => {
if (_ref) {
// Use _ref
} else {
// Clean up _ref
}
}} />
```
In `<StrictMode>` in dev hooks are run twice on each render.
For `useId` the re-render pass uses the `updateId` implementation rather
than `mountId`. In the update path we don't increment the local id
counter. This causes the render to look like no id was used which
changes the tree context and leads to a different set of IDs being
generated for subsequent calls to `useId` in the subtree.
This was discovered here: https://github.com/vercel/next.js/issues/43033
It was causing a hydration error because the ID generation no longer
matched between server and client. When strict mode is off this does not
happen because the hooks are only run once during hydration and it
properly sees that the component did generate an ID.
The fix is to not reset the localIdCounter in `renderWithHooksAgain`. It
gets reset anyway once the `renderWithHooks` is complete and since we do
not re-mount the ID in the `...Again` pass we should retain the state
from the initial pass.
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## Summary
Submit https://github.com/facebook/react/pull/25698 again after fixing
the devtools regression tests in CI.
The PR changed lanes representation and some snapshot tests of devtools
captures lanes. In devtools tests for older versions, the updated lanes
representation no longer matched. The fix is to disable regression tests
for those tests.
## How did you test this change?
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```
./scripts/circleci/download_devtools_regression_build.js 18.0 --replaceBuild
node ./scripts/jest/jest-cli.js --build --project devtools --release-channel=experimental --reactVersion 18.0
```
Unrelated to this PR. There was some issue with jest caching when I
locally ran that command. it didn't seem to include the @reactVersion
transform, but if I manually modified `scripts/jest/preprocessor.js` or
ran ` yarn test --clearCache`, the jest test runs correctly.
## Edit
Went for another approach after talking with @gnoff. The approach is
now:
- add a dev-only error when a precomputed chunk is too big to be written
- suggest to copy it before passing it to `writeChunk`
This PR also includes porting the React Float tests to use the browser
build of Fizz so that we can test it out on that environment (which is
the one used by next).
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## Summary
Someone reported [a bug](https://github.com/vercel/next.js/issues/42466)
in Next.js that pointed to an issue with Node 18 in the streaming
renderer when using importing a CSS module where it only returned a
malformed bootstraping script only after loading the page once.
After investigating a bit, here's what I found:
- when using a CSS module in Next, we go into this code path, which
writes the aforementioned bootstrapping script
https://github.com/facebook/react/blob/5f7ef8c4cbe824ef126a947b7ae0e1c07b143357/packages/react-dom-bindings/src/server/ReactDOMServerFormatConfig.js#L2443-L2447
- the reason for the malformed script is that
`completeBoundaryWithStylesScript1FullBoth` is emptied after the call to
`writeChunk`
- it gets emptied in `writeChunk` because we stream the chunk directly
without copying it in this codepath
https://github.com/facebook/react/blob/a438590144d2ad40865b58e0c0e69595fc1aa377/packages/react-server/src/ReactServerStreamConfigBrowser.js#L63
- the reason why it only happens from Node 18 is because the Webstreams
APIs are available natively from that version and in their
implementation, [`enqueue` transfers the array buffer
ownership](https://github.com/nodejs/node/blob/9454ba6138d11e8a4d18b073de25781cad4bd2c8/lib/internal/webstreams/readablestream.js#L2641),
thus making it unavailable/empty for subsequent calls. In older Node
versions, we don't encounter the bug because we are using a polyfill in
Next.js, [which does not implement properly the array buffer transfer
behaviour](https://cs.github.com/MattiasBuelens/web-streams-polyfill/blob/d354a7457ca8a24030dbd0a135ee40baed7c774d/src/lib/abstract-ops/ecmascript.ts#L16).
I think the proper fix for this is to clone the array buffer before
enqueuing it. (we do this in the other code paths in the function later
on, see ```((currentView: any): Uint8Array).set(bytesToWrite,
writtenBytes);```
## How did you test this change?
Manually tested by applying the change in the compiled Next.js version.
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Co-authored-by: Sebastian Markbage <sebastian@calyptus.eu>
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## Summary
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For more context: https://github.com/facebook/react/pull/25692
Based on https://github.com/facebook/react/pull/25695. This PR adds the
`SyncHydrationLane` so we rewind on sync updates during selective
hydration. Also added tests for ContinuouseHydration and
DefaultHydration lanes.
## How did you test this change?
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yarn test
Now that hook state is preserved while the work loop is suspended, we
don't need to track the thenable state in the work loop. We can track
it alongside the rest of the hook state.
This is a nice simplification and also aligns better with how it works
in Fizz and Flight.
The promises will still be cleared when the component finishes rendering
(either complete or unwind). In the future, we could stash the promises
on the fiber and reuse them during an update. However, this would only
work for `use` calls that occur before an prop/state/context is
processed, because `use` calls can only be assumed to execute in the
same order if no other props/state/context have changed. So it might not
be worth doing until we have finer grained memoization.
Now that hook state is preserved while the work loop is suspended, we
don't need to track the thenable state in the work loop. We can track
it alongside the rest of the hook state.
Before deleting the thenable state variable from the work loop, I need
to remove the other places where it's referenced.
One of them is `isThenableStateResolved`. This grabs the last thenable
from the array and checks if it has resolved.
This was a pointless indirection anyway. The thenable is already stored
as `workInProgressThrownValue`. So we can check that directly.
When a component suspends, under some conditions, we can wait for the
data to resolve and replay the component without unwinding the stack or
showing a fallback in the interim. When we do this, we reuse the
promises that were unwrapped during the previous attempts, so that if
they aren't memoized, the result can still be used.
We should do the same for all hooks. That way, if you _do_ memoize an
async function call with useMemo, it won't be called again during the
replay. This effectively gives you a local version of the functionality
provided by `cache`, using the normal memoization patterns that have
long existed in React.
Currently, if you call setState in render, you must render the exact
same hooks as during the first render pass.
I'm about to add a behavior where if something suspends, we can reuse
the hooks from the previous attempt. That means during initial render,
if something suspends, we should be able to reuse the hooks that were
already created and continue adding more after that. This will error
in the current implementation because of the expectation that every
render produces the same list of hooks.
In this commit, I've changed the logic to allow more hooks to be added
when replaying. But only during a mount — if there's already a current
fiber, then the logic is unchanged, because we shouldn't add any
additional hooks that aren't in the current fiber's list. Mounts are
special because there's no current fiber to compare to.
I haven't change any other behavior yet. The reason I've put this into
its own step is there are a couple tests that intentionally break the
Hook rule, to assert that React errors in these cases, and those happen
to be coupled to the behavior. This is undefined behavior that is always
accompanied by a warning and/or error. So the change should be safe.
When replaying a suspended function components, we want to reuse the
hooks that were computed during the original render.
Currently we reset the state of the hooks right after the component
suspends (or throws an error). This is too early because it doesn't
give us an opportunity to wait for the promise to resolve.
This refactors the work loop to reset the hooks right before unwinding
instead of right after throwing. It doesn't include any other changes
yet, so there should be no observable behavioral change.
Before suspending, check if there are other pending updates that might
possibly unblock the suspended component. If so, interrupt the current
render and switch to working on that.
This logic was already implemented for the old "throw a Promise"
Suspense but has to be replicated for `use` because it suspends the
work loop much earlier.
I'm getting a little anxious about the divergence between the two
Suspense patterns. I'm going to look into enabling the new behavior for
the old pattern so that we can unify the implementations.
When an update flows into a dehydrated boundary, React cannot apply the
update until the boundary has finished hydrating. The way this currently
works is by scheduling a slightly higher priority task on the boundary,
using a special lane that's reserved only for this purpose. Because the
task is slightly higher priority, on the next turn of the work loop, the
Scheduler will force the work loop to yield (i.e. shouldYield starts
returning `true` because there's a higher priority task).
The downside of this approach is that it only works when time slicing is
enabled. It doesn't work for synchronous updates, because the
synchronous work loop does not consult the Scheduler on each iteration.
We plan to add support for selective hydration during synchronous
updates, too, so we need to model this some other way.
I've added a special internal exception that can be thrown to force the
work loop to interrupt the work-in-progress tree. Because it's thrown
from a React-only execution stack, throwing isn't strictly necessary —
we could instead modify some internal work loop state. But using an
exception means we don't need to check for this case on every iteration
of the work loop. So doing it this way moves the check out of the fast
path.
The ideal implementation wouldn't need to unwind the stack at all — we
should be able to hydrate the subtree and then apply the update all
within a single render phase. This is how we intend to implement it in
the future, but this requires a refactor to how we handle "stack"
variables, which are currently pushed to a per-render array. We need to
make this stack resumable, like how context works in Flight and Fizz.
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.
This micro-optimization never made sense and less so now that they're
rare.
This still initializes the class with a shared immutable object in the
constructor - which is also what createClass() does.
Then we override it during mount. This is done in case someone messes up
the initialization of the super() constructor for example, which was
more common in polyfills.
This change means that if a ref is initialized during the constructor
itself it wouldn't be lazily initialized but that's not user code that
does it, it's React so that shouldn't happen.
This makes string refs codemoddable as described in.
https://github.com/facebook/react/pull/25334
Some old environments like IE11 or very old versions of jsdom are
missing `getRootNode()`. Use feature detection to fall back to
`ownerDocuments` in these environments that also won't be supporting
shadow DOM anyway.
This just removes the error but the underlying issue is still there, and
it's likely that the best course of action is to not update in effects
and to wrap most updates in startTransition. However, that's more of a
performance concern which is not something we generally do even in
recoverable errors since they're less actionable and likely belong in
another channel. It is also likely that in many cases this happens so
rarely because you have to interact quickly enough that it can often be
ignored.
After changes to other parts of the model, this only happens for
sync/discrete updates. There are three scenarios that can happen:
- We replace a server rendered fallback with a client rendered fallback.
Other than this potentially causing some flickering in the loading
state, it's not a big deal.
- We replace the server rendered content with a client side fallback if
this suspends on the client. This is in line with what would happen
anyway. We will loose state of forms which is not intended semantics.
State and animations etc would've been lost anyway if it was client-side
so that's not a concern.
- We replace the server rendered content with a client side rendered
tree and lose selection/state and form state. While the content looks
the same, which is unfortunate.
In most scenarios it's a bad loading state but it's the same scenario as
flushing sync client-side. So it's not so bad.
The big change here is that we consider this a bug of React that we
should fix. Therefore it's not actionable to users today because it
should just get fixed. So we're removing the error early. Although
anyone that has fixed these issues already are probably better off for
it.
To fix this while still hydrating we need to be able to rewind a sync
tree and then replay it.
@tyao1 is going to add a Sync hydration lane. This is will allow us to
rewind the tree when we hit this state, and replay it given the previous
Context, hydrate and then reapply the update. The reason we didn't do
this originally is because it causes sync mode to unwind where as for
backwards compatibility we didn't want to cause that breaking semantic -
outside Suspense boundaries - and we don't want that semantic longer
term. We're only do this as a short term fix.
We should also have a way to leave a partial tree in place. If the sync
hydration lane suspends, we should be able to switch to a client side
fallback without throwing away the state of the DOM and then hydrate
later.
We now know how we want to fix this longer term. We're going to move all
Contexts into resumable trees like what Fizz/Flight does. That way we
can leave the original Context at the hydration boundaries and then
resume from there. That way the rewinding would never happen even in the
existence of a sync hydration lane which would only apply locally to the
dehydrated tree.
So the steps are 1) remove the error 2) add the sync hydration lane with
rewinding 3) Allow hiding server-rendered content while still not
hydrated 4) add resumable contexts at these boundaries.
Fixes#25625 and #24959.
## Summary
This PR is to fix a bug: an "element cannot be found" error when
hydrating Server Components
### The problem
<img width="1061" alt="image"
src="https://user-images.githubusercontent.com/1001890/201206046-ac32a5e3-b08a-4dc2-99f4-221dad504b28.png">
To reproduce:
1. setting up a vercel next.js 13 playground locally
https://github.com/vercel/app-playground
2. visit http://localhost:3000/loading
3. click "electronics" button to navigate to
http://localhost:3000/loading/electronics to trigger hydrating
4. inspect one of the skeleton card UI from React DevTools extension
### The root cause & fix
This bug was introduced in #22527. When syncing reconciler changes, the
value of `Hydrating` was copied from another variable `Visibility` (one
more zero in the binary number).
To avoid this kind of issue in the future, a new file `ReactFiberFlags`
is created following the same format of the one in reconciler, so that
it's easier to sync the number without making mistakes.
The reconciler fiber flag file is also updated to reflect which of the
flags are used in devtools
## How did you test this change?
I build it locally and the bug no longer exist on
http://localhost:3000/loading
Nested Offscreens can run into a case where outer Offscreen is revealed
while inner one is hidden in a single commit. This is an edge case that
was previously missed. We need to prevent call to disappear layout
effects.
When we go from state:
```jsx
<Offscreen mode={'hidden'}> // outer offscreen
<Offscreen mode={'visible'}> // inner offscreen
{children}
</Offscreen>
</Offscreen>
```
To following. Notice that visibility of each offscreen flips.
```jsx
<Offscreen mode={'visible'}> // outer offscreen
<Offscreen mode={'hidden'}> // inner offscreen
{children}
</Offscreen>
</Offscreen>
```
Inner offscreen must not call
`recursivelyTraverseDisappearLayoutEffects`.
Check unit tests for an example of this.
This is a follow up on https://github.com/facebook/react/pull/25592
There is another condition Offscreen calls
`recursivelyTraverseDisappearLayoutEffects` when it shouldn't. Offscreen
may be nested. When nested Offscreen is hidden, it should only unmount
layout effects if it meets following conditions:
1. This is an update, not first mount.
2. This Offscreen was hidden before.
3. No ancestor Offscreen is hidden.
Previously, we were not accounting for the third condition.
I don't think we need this anymore. It was added originally because
RootSuspended would take priority over RootSuspendedWithDelay. But we've
since changed it: any "bad" fallback state is permitted to block a
"good" fallback state.
The other status flags that this check used to account for are
RootDidNotComplete and RootFatalErrored:
- RootFatalErrored is like an invariant violation, it means something
went really wrong already and we can't recover from it
- RootCompleted and RootDidNotComplete are only set at the very end of
the work loop, there's no way for renderDidSuspendDelayIfPossible to
sneak in after that (at least none that I can think of — it's only
called from the render phase)
So I think we can just delete this.
It's entirely possible there's some scenario I haven't considered,
though, which is why I'm submitting this change as its own PR. To
preserve the ability to bisect to it later.
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Following
[comment](https://github.com/facebook/react/pull/25437#discussion_r1010944983)
in #25437 , the external runtime implementation should be moved from
`react-dom` to `react-dom-bindings`.
I did have a question here:
I set the entrypoint to `react-dom/unstable_server-external-runtime.js`,
since a.) I was following #25436 as an example and b.)
`react-dom-bindings` was missing a `README.md` and `npm/`. This also
involved adding the external runtime to `package.json`.
However, the external runtime isn't really a `react-dom` entrypoint. Is
this change alright, or should I change the bundling code instead?
## How did you test this change?
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type validateDOMNesting
move `isHostResourceType` to ReactDOMHostConfig
type `AncestorInfo`
refactor `resourceFormOnly` into `ancestorInfo.containerTagInScope`
provide hostContext from reconciler
Makes it slightly more blazing.
No host config actually uses null as any useful and we use this as a
placeholder value anyway. It's also better for perf since it doesn't let
two different hidden classes pass around. It's also a magic place holder
that triggers error if we do try to access anything from it.
`title` is a valid element descendent of `svg`. this PR adds a
prohibition on turning titles in svg into Resources.
This PR also adds additional warnings if you render something that is
almost a Resource inside an svg.
Initial draft. I need to test this more.
If a promise is passed to `use`, but the I/O isn't cached, we should
still be able to unwrap it.
This already worked in Server Components, and during SSR.
For Fiber (in the browser), before this fix the state would get lost
between attempts unless the promise resolved immediately in a microtask,
which requires IO to be cached. This was due to an implementation quirk
of Fiber where the state is reset as soon as the stack unwinds. The
workaround is to suspend the entire Fiber work loop until the promise
resolves.
The Server Components and SSR runtimes don't require a workaround: they
can maintain multiple parallel child tasks and reuse the state
indefinitely across attempts. That's ideally how Fiber should work, too,
but it will require larger refactor.
The downside of our approach in Fiber is that it won't "warm up" the
siblings while you're suspended, but to avoid waterfalls you're supposed
to hoist data fetches higher in the tree regardless. But we have other
ideas for how we can add this back in the future. (Though again, this
doesn't affect Server Components, which already have the ideal
behavior.)
`wasHidden` is evaluted to false if `current` is null. This means
Offscreen has never been shown but this code assumes it is going from
'visible' to 'hidden' and unmounts layout effects.
To fix this, only unmount layout effects if `current` is not null.
I'm not able to repro this problem or write unit test for it. I see this
crash bug in production test.
The problem with repro is that if Offscreen starts as hidden, it's
render is deferred and current is no longer null.
Pure refactor, no change in behavior.
Extracts the logic for detecting whether a suspended component will
result in a "bad" Suspense fallback into a helper function. An example
of a bad Suspense fallback is one that causes already-visible content
to disappear.
I want to reuse this same logic in the work loop, too.
Refactors the logic for handling when the work loop is suspended into
separate functions for replaying versus unwinding. This allows us to
hoist certain checks into the caller.
For example, when rendering due to flushSync, we will always unwind the
stack without yielding the microtasks.
No intentional behavior change in this commit.
This is a pure refactor, no change to behavior.
When a component throws, the work loop can handle that in one of several
ways — unwind immediately, wait for microtasks, and so on. I'm about
to add another one, too. So I've changed the variable that tracks
whether the work loop is suspended from a boolean
(workInProgressIsSuspended) to an enum (workInProgressSuspendedReason).
In Strict Mode, during development, user functions are double invoked to
help detect side effects. Currently, the way we implement this is to
completely discard the first pass and start over. Theoretically this
should be fine because components are idempotent. However, it's a bit
tricky to get right because our implementation (i.e. `renderWithHooks`)
is not completely idempotent with respect to internal data structures,
like the work-in-progress fiber. In the past we've had to be really
careful to avoid subtle bugs — for example, during the initial mount,
`setState` functions are bound to the particular hook instances that
were created during that render. If we compute new hook instances, we
must also compute new children, and they must correspond to each other.
This commit addresses a similar issue that came up related to `use`:
when something suspends, `use` reuses the promise that was passed during
the first attempt. This is itself a form of memoization. We need to be
able to memoize the reactive inputs to the `use` call using a hook (i.e.
`useMemo`), which means, the reactive inputs to `use` must come from the
same component invocation as the output.
The solution I've chosen is, rather than double invoke the entire
`renderWithHook` function, we should double invoke each individual user
function. It's a bit confusing but here's how it works:
We will invoke the entire component function twice. However, during the
second invocation of the component, the hook state from the first
invocation will be reused. That means things like `useMemo` functions
won't run again, because the deps will match and the memoized result
will be reused.
We want memoized functions to run twice, too, so account for this, user
functions are double invoked during the *first* invocation of the
component function, and are *not* double invoked during the second
incovation:
- First execution of component function: user functions are double
invoked
- Second execution of component function (in Strict Mode, during
development): user functions are not double invoked.
It's hard to explain verbally but much clearer when you run the test
cases I've added.
The old (unstable) mechanism for suspending was to throw a promise. The
purpose of throwing is to interrupt the component's execution, and also
to signal to React that the interruption was caused by Suspense as
opposed to some other error.
A flaw is that throwing is meant to be an implementation detail — if
code in userspace catches the promise, it can lead to unexpected
behavior.
With `use`, userspace code does not throw promises directly, but `use`
itself still needs to throw something to interrupt the component and
unwind the stack.
The solution is to throw an internal error. In development, we can
detect whether the error was caught by a userspace try/catch block and
log a warning — though it's not foolproof, since a clever user could
catch the object and rethrow it later.
The error message includes advice to move `use` outside of the try/catch
block.
I did not yet implement the warning in Flight.
stacked on https://github.com/facebook/react/pull/25569
On the client noscript already never renders children so no resources
will be extracted from this context. On the server we now track if we
are in a noscript context and turn off Resource semantics in this scope
Jan Kassens
Sebastian Silbermann
Mengdi Chen
mofeiZ
Samuel Susla
Josh Story
Tianyu Yao
Jimmy Lai
Colin McDonnell
Andrew Clark
Sebastian Markbåge
Aurélien Chivot-Buhler
