Uh oh!
There was an error while loading. Please reload this page.
Warn about async infinite useEffect loop - #15180
Merged
Merged
Conversation
gaearon
commented
Mar 21, 2019
| while (error === null) { | ||
| Scheduler.unstable_flushNumberOfYields(1); | ||
| await Promise.resolve(); | ||
| } |
CollaboratorAuthor
There was a problem hiding this comment.
This is my shoddy attempt to faithfully emulate deferreduseEffect case. (I don't want to flush it all synchronously.)
idontknowwhatimdoing.jpg
Collaborator
There was a problem hiding this comment.
Try this
ReactDOM.render(<App/>,container,()=>Scheduler.yieldValue('Did commit'));expect(Scheduler).toFlushAndYieldThrough(['Did commit']);// Synchronous effect has run, but not passive effects.// Now flush the effects:Scheduler.flushAll();Collaborator
There was a problem hiding this comment.
Actually I forgot this is sync mode. Might be easier to use a boolean since the effect runs an arbitrary number of times before erroring.
ReactDOM.render(<App/>,container);expect(container.textContent).toEqual(whatever);// Synchronous effect has run, but not passive effects.expect(didFlushPassiveEffect).toBe(false);// Now flush the effects:Scheduler.flushAll();CollaboratorAuthor
There was a problem hiding this comment.
I wanted to simulate a real deferred loop between them to make sure the warning still fires. Not sure if it matters.
Collaborator
There was a problem hiding this comment.
To do that you need an assertion in between the synchronous commit phase and the effect phase. As is, your test would pass even if the passive effects were totally sync.
gaearon
commented
Mar 21, 2019
| } | ||
| if (__DEV__) { | ||
| if (rootWithPendingPassiveEffects === root) { |
CollaboratorAuthor
There was a problem hiding this comment.
Only keep incrementing if flushing root's deferred effects schedules the same root again.
Details of bundled changes.Comparing: 3151813...9cdb8c4 react-dom
react-art
react-native-renderer
react-test-renderer
react-reconciler
Generated by 🚫 dangerJS |
acdlite
reviewed
Mar 21, 2019
| const container = document.createElement('div'); | ||
| ReactDOM.render(<App />, container); | ||
| while (error === null) { | ||
| Scheduler.unstable_flushNumberOfYields(1); |
Collaborator
There was a problem hiding this comment.
Since the first yieldValue call happens in a passive effect, this actually will flush the effects synchronously
acdlite
reviewed
Mar 21, 2019
| ReactDOM.render(<App />, container); | ||
| while (error === null) { | ||
| Scheduler.unstable_flushNumberOfYields(1); | ||
| await Promise.resolve(); |
acdlite
approved these changes
Mar 22, 2019
Merged
This was referenced Aug 17, 2019
This was referenced Mar 10, 2020
This was referenced Mar 18, 2020
mrizwanashiq pushed a commit
to mrizwanashiq/react
that referenced
this pull request
Jun 25, 2026
* Warn about async infinite useEffect loop * Make tests sync
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
Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment
4 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 surfaces problems like #14920 (comment) where the same root keeps scheduling updates inside useEffect, and never manages to "rest". It only catches the "synchronous" case (setState directly in useEffect).
I've made it DEV-only because a crash would be a breaking change. The heuristic might also not be perfect yet and I'd like to give it some time to see if there are edge false positives.