[Flight] Resolve deduped references when chunks are blocked on each other #32316
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
github-actions
bot
added
the
React Core Team
unstubbable
added a commit
to unstubbable/react
that referenced
this pull request
Feb 6, 2025
unstubbable
added a commit
to unstubbable/react
that referenced
this pull request
Feb 7, 2025
unstubbable
changed the title
unstubbable
force-pushed
the
client-component-props-deduping
branch
from
414c443 to
ecb5a8a
Compare
eps1lon
reviewed
Feb 9, 2025
packages/react-server-dom-webpack/src/__tests__/ReactFlightDOMBrowser-test.js
Show resolved
Hide resolved
sebmarkbage
reviewed
Feb 10, 2025
| reason: null | Array<(mixed) => mixed>, | ||
| intermediaryValue?: mixed, | ||
| _response: Response, | ||
| _children: Array<SomeChunk<any>> | ProfilingResult, // Profiling-only |
Collaborator
There was a problem hiding this comment.
This is not "Profiling-only" anymore. I'm not sure this is actually reliable enough. It's more of a hack for profiling which is optional if it works or not.
Collaborator
Author
There was a problem hiding this comment.
I think we can keep _children profiling-only. It was not necessary for this fix to remove the two guards around initializingChunk._children. I reverted that.
sebmarkbage
reviewed
Feb 11, 2025
| function createFromJSONCallback(response: Response) { | ||
| // $FlowFixMe[missing-this-annot] | ||
| return function (key: string, value: JSONValue) { | ||
| isParsingRootModel = key === ''; |
Collaborator
There was a problem hiding this comment.
We can't assume that an empty string key is the root since it may also be on nested objects. What's the implication of that?
Collaborator
Author
There was a problem hiding this comment.
Hmm, we were already using the check here:
react/packages/react-client/src/ReactFlightClient.js
Lines 983 to 987 in 192555b
But I guess you're right, it could also be an explicit empty key in some object.
unstubbable
added a commit
to sebmarkbage/react
that referenced
this pull request
Jun 29, 2025
sebmarkbage
pushed a commit
to sebmarkbage/react
that referenced
this pull request
Jun 29, 2025
sebmarkbage
added a commit
to sebmarkbage/react
that referenced
this pull request
Jun 29, 2025
Stacked on facebook#33666. If we ever get a future reference to a cycle and that reference gets eagerly parsed before the target has loaded then we can end up with a cycle that never gets resolved. That's because our cycle resolution only works if the cyclic future reference is created synchronously within the parsing path of the child. I haven't been able to construct a normal scenario where this would break. So this doesn't fail any tests. However, I can construct it with debug info since those are eagerly evaluated. It's also a prerequisite if the debug data can come out of order, like if it's on a different stream. The fix here is to make all the internal dependencies in the "listener" list into introspectable objects instead of closures. That way we can traverse the list of dependencies of a blocked reference to see if it ends up in a cycle and therefore skip the reference. It would be nice to address this once and for all to be more resilient to server changes, but I'm not sure if it's worth this complexity and the extra CPU cost of tracing the dependencies. Especially if it's just for debug data. closes facebook#32316 fixes vercel/next.js#72104 --------- Co-authored-by: Hendrik Liebau <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
5 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This PR includes a reduced test case of vercel/next.js#75726:
This is serialized into the following RSC payload which the Flight Client was not able to resolve, because two chunks are blocked on each other:
We can fix this by storing intermediary values (only elements for now) on the initializing chunk. When the
fulfilllistener inwaitForReferenceis called with a lazy element that has a blocked chunk, which is not the current chunk, we can peek into the intermediary value of the referenced chunk to resolve a reference for a different chunk that's still blocked.fixes vercel/next.js#72104