[compiler runtime] repro: infinite render with useMemoCache + render phase updates #30849
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Outdated suggestions cannot be applied.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.
Repro for an infinite render bug we found when testing internally. See equivalent codesandbox repro here.
When render phase updates cause a re-render, useMemoCache arrays for the fiber are cleared and recreated on every retry while hook state is preserved.
This pattern (queuing re-renders on the current fiber during render) is perfectly valid. I believe this is a bug as React compiler currently replaces
useMemo
s withuseMemoCache
calls and inlined instructions, taking care to preserve existing memoization dependencies. This should be the identity transform, but runtime implementation differences mean that uncompiled code behaves as expected (no infinite render) while compiled code fails to render.