* Do not fix return pointers during commit phase
In the commit phase, we should be able to assume that the `return`
pointers in the just-completed tree are consistent. The render phase
should be responsible for ensuring these are always correct.
I've removed the `return` pointer assignments from the render phase
traversal logic. This isn't all of them, only the ones added recently
during the effects refactor. The other ones have been around longer so
I'll leave those for a later clean up.
This breaks a few SuspenseList tests; I'll fix in the next commit.
* Set return pointer when reusing current tree
We always set the return pointer on freshly cloned, work-in-progress
fibers. However, we were neglecting to set them on trees that are reused
from current.
I fixed this in the same path of the complete phase where we reset the
fiber flags.
This is a code smell because it assumes the commit phase is never
concurrent with the render phase. Our eventual goal is to make fibers a
lock free data structure.
Will address further during refactor to alternate model.
Background:
State updates that are scheduled in a layout effect (useLayoutEffect or componentDidMount / componentDidUpdate) get processed synchronously by React before it yields to the browser to paint. This is done so that components can adjust their layout (e.g. position and size a tooltip) without any visible shifting being seen by users. This type of update is often called a "nested update" or a "cascading update".
Because they delay paint, nested updates are considered expensive and should be avoided when possible. For example, effects that do not impact layout (e.g. adding event handlers, logging impressions) can be safely deferred to the passive effect phase by using useEffect instead.
This PR updates the Profiler API to explicitly flag nested updates so they can be monitored for and avoided when possible.
Implementation:
I considered a few approaches for this.
Add a new callback (e.g. onNestedUpdateScheduled) to the Profiler that gets called when a nested updates gets scheduled.
Add an additional boolean parameter to the end of existing callbacks (e.g. wasNestedUpdate).
Update the phase param to add an additional variant: "mount", "update", or "nested-update" (new).
I think the third option makes for the best API so that's what I've implemented in this PR.
Because the Profiler API is stable, this change will need to remain behind a feature flag until v18. I've turned the feature flag on for Facebook builds though after confirming that Web Speed does not currently make use of the phase parameter.
Quirks:
One quirk about the implementation I've chosen is that errors thrown during the layout phase are also reported as nested updates. I believe this is appropriate since these errors get processed synchronously and block paint. Errors thrown during render or from within passive effects are not affected by this change.
This reverts commits bcca5a6ca7 and ffb749c95e, although neither revert cleanly since methods have been moved between the work-loop and commit-work files. This commit is a mostly manual effort of undoing the changes.
This adds a new dimension similar to dom-relay. It's different from
"native" which would be Flight for RN without Relay.
This has some copy-pasta that's the same between the two Relay builds but
the key difference will be Metro and we're not quite sure what other
differences there will be yet.
* Remove Blocks
* Remove Flight Server Runtime
There's no need for this now that the JSResource is part of the bundler
protocol. Might need something for Webpack plugin specifically later.
* Devtools
This now means that if a server component suspends, its value becomes a
React.lazy object. I.e. the element that rendered the server component
gets replaced with a lazy node.
As of #19033 lazy objects can be rendered in the node position. This allows
us to suspend at the location of the server component while we're waiting
on its content.
Now server components has the same capabilities as Blocks to progressively
reveal its content.
These references are currently transformed into React.lazy values. We can use these in
React positions like element type or node position.
This could be expanded to a more general concept like Suspensey Promises, asset references or JSResourceReferences.
For now it's only used in React Element type position.
The purpose of these is to let you suspend deeper in the tree.
* Refactor Flight to require a module reference to be brand checked
This exposes a host environment (bundler) specific hook to check if an
object is a module reference. This will be used so that they can be passed
directly into Flight without needing additional wrapper objects.
* Emit module references as a special type of value
We already have JSON and errors as special types of "rows". This encodes
module references as a special type of row value. This was always the
intention because it allows those values to be emitted first in the stream
so that as a large models stream down, we can start preloading as early
as possible.
We preload the module when they resolve but we lazily require them as they
are referenced.
* Emit module references where ever they occur
This emits module references where ever they occur. In blocks or even
directly in elements.
* Don't special case the root row
I originally did this so that a simple stream is also just plain JSON.
However, since we might want to emit things like modules before the root
module in the stream, this gets unnecessarily complicated. We could add
this back as a special case if it's the first byte written but meh.
* Update the protocol
* Add test for using a module reference as a client component
* Relax element type check
Since Flight now accepts a module reference as returned by any bundler
system, depending on the renderer running. We need to drastically relax
the check to include all of them. We can add more as we discover them.
* Move flow annotation
Seems like our compiler is not happy with stripping this.
* Some bookkeeping bug
* Can't use the private field to check
In some scenarios (either timing dependent, or pre-FR compatible React versions) FR blocked calling the React DevTools commit hook. This PR adds a test and a fix for that.
Adds a bunch of no-inline directives to commit phase functions to
prevent them from being inlined into one of our recursive algorithms.
The motivation is to minimize the number of variables in the recursive
functions, since each one contributes to the size of the stack frame.
Theoretically, this could help the performance of both the recursive
and non-recursive (iterative) implementations of the commit phase,
since even the iterative implementation sometimes uses the JS stack.
* Move traversal logic to ReactFiberCommitWork
The current traversal logic is spread between ReactFiberWorkLoop and
ReactFiberCommitWork, and it's a bit awkward, especially when
refactoring. Idk the ideal module structure, so for now I'd rather keep
it all in one file.
* Traverse commit phase effects iteratively
We suspect that using the JS stack to traverse through the tree in the
commit phase is slower than traversing iteratively.
I've kept the recursive implementation behind a flag, both so we have
the option to run an experiment comparing the two, and so we can revert
it easily later if needed.
Reading or writing a ref value during render is only safe if you are implementing the lazy initialization pattern.
Other types of reading are unsafe as the ref is a mutable source.
Other types of writing are unsafe as they are effectively side effects.
This change also refactors useTransition to no longer use a ref hook, but instead manage its own (stable) hook state.
* Add Visibility flag for hiding/unhiding trees
There's `beforeblur` logic in the snapshot phase that needs to visit
every Suspense boundary whose visibility is toggled. Right now it does
that by visiting Placement and Deletion effects. That includes many
unrelated nodes.
By adding a new flag specifically for toggling Visibility, we will only
visit the relevant Suspense (and Offscreen) boundaries, instead of all
nodes that have a Placement.
Potential follow-ups (not urgent):
- The `beforeblur` logic also has a check to see whether the visibility
was toggled on or off. It only cares about things being hidden. As a
follow up, I can split the Visibility flag into separate Hide/Show
flags, and only visit Hide.
- Now that this is separate from Update, we can move the rest of the
Suspense's layout effects (like attaching retry listeners) to the
passive phase.
* Gate behind createEventHandle feature flag
Only need to visit deleted and hidden trees during the snapshot phase
if the experimental `createEventHandle` flag is enabled. Currently,
it's only used internally at Facebook, not open source.
* Remove dead code branch
This function is only called when initializing roots/containers (where we skip non-delegated events) and in the createEventHandle path for non-DOM nodes (where we never hit this path because targetElement is null).
* Move related functions close to each other
* Fork listenToNativeEvent for createEventHandle
It doesn't need all of the logic that's needed for normal event path.
And the normal codepath doesn't use the last two arguments.
* Expand test coverage for non-delegated events
This changes a test to fail if we removed the event handler Sets. Previously, we didn't cover that.
* Add DEV-level check that top-level events and non-delegated events do not overlap
This makes us confident that they're mutually exclusive and there is no duplication between them.
* Add a test verifying selectionchange deduplication
This is why we still need the Set bookkeeping. Adding a test for it.
* Remove Set bookkeeping for root events
Root events don't intersect with non-delegated bubbled events (so no need to deduplicate there). They also don't intersect with createEventHandle non-managed events (because those don't go on the DOM elements). So we can remove the bookeeping because we already have code ensuring the eager subscriptions only run once per element.
I've moved the selectionchange special case outside, and added document-level deduplication for it alone.
Technically this might change the behavior of createEventHandle with selectionchange on the document, but we're not using that, and I'm not sure that behavior makes sense anyway.
* Flow
* bump package to latest
* update files to respect lint
* disable object-type-delimiter rule to work with prettier
* disable rule to let flow check pass
We don't need to visit passive effect nodes during before mutation.
The only reason we were previously was to schedule the root-level
passive effect callback as early as possible, but now that
`subtreeFlags` exists, we can check that instead.
This should reduce the amount of traversal during the commit phase,
particularly when mounting or updating large trees that contain many
passive effects.
Large legacy applications are likely to be difficult to update to handle this feature, and it wouldn't add any value– since newer APIs that require this resilience are not legacy compatible.
This is done so that any effects scheduled by the shallow render are thrown away.
Unlike the code this was forked from (in ReactComponentStackFrame) DevTools should override the dispatcher even when DevTools is compiled in production mode, because the app itself may be in development mode and log errors/warnings.
* update all facebook.github.io links
* facebookincubator links : update some outdated links and fix two other broken links where they are actually the latest updated ones
Andrew Clark
Ricky
Brian Vaughn
Sean Keenan
inokawa
Jack Works
Deniz Susman
Sebastian Markbåge
Sy Tran Dung
Abhyuday Bharat
Dan Abramov
Dan Abramov
Kai Riemann
Sebastian Silbermann
oltrep
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adasq
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