Fix priority of clean-up function on deletion #16277
Merged
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
The clean-up function of a passive effect (`useEffect`) usually fires in a post-commit task, after the browser has painted. However, there is an exception when the component (or its parent) is deleted from the tree. In that case, we fire the clean-up function during the synchronous commit phase, the same phase we use for layout effects. This is a concession to implementation complexity. Calling it in the passive effect phase would require either traversing the children of the deleted fiber again, or including unmount effects as part of the fiber effect list. Because the functions are called during the sync phase in this case, the Scheduler priority is Immediate (the one used for layout) instead of Normal. We may want to reconsider this trade off later.
|
ReactDOM: size: 0.0%, gzip: -0.0% Details of bundled changes.Comparing: f440bfd...7df2aa6 react-art
react-native-renderer
react-dom
react-test-renderer
react-reconciler
Generated by 🚫 dangerJS |
sebmarkbage
approved these changes
Aug 2, 2019
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
The clean-up function of a passive effect (
useEffect) usually fires in a post-commit task, after the browser has painted. However, there is an exception when the component (or its parent) is deleted from the tree. In that case, we fire the clean-up function during the synchronous commit phase, the same phase we use for layout effects.This is a concession to implementation complexity. Calling it in the passive effect phase would require either traversing the children of the deleted fiber again, or including unmount effects as part of the fiber effect list.
Because the functions are called during the sync phase in this case, the Scheduler priority is Immediate (the one used for layout) instead of Normal. We may want to reconsider this trade off later.
In practice, this should rarely matter because it's unusual to call
setStateinside a clean-up function. We might want to warn about this pattern.