fix: Race condition in withFeatureFlagsOverrideDecorator#584
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…deDecorator (#571) Add resetTransaction() to EditableLaunchDarklyClient to safely undo any lingering transaction before starting a new one. This fixes a race condition where a new OverrideFeatureFlags instance renders (calling startTransaction()) before the old instance's useEffect cleanup has run. Neither useLayoutEffect nor useEffect can fix this because React's render phase always executes before the commit phase where cleanup runs. Also add ForceRemount regression stories that deterministically trigger the race condition via a React key change to prevent regressions. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Patrick Lafrance (patricklafrance)
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Patrick Lafrance (patricklafrance)
April 3, 2026 02:46
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Pull request overview
Fixes a Storybook crash caused by a LaunchDarkly transaction race when withFeatureFlagsOverrideDecorator is unmounted/remounted before effect cleanup runs.
Changes:
- Add
resetTransaction()toEditableLaunchDarklyClientand implement it in the in-memory and local-storage clients. - Update
withFeatureFlagsOverrideDecoratorto callresetTransaction()during render and avoid double-undo()on cleanup. - Add Storybook sample stories that force a remount to reproduce/regress the original crash (both in-memory and local-storage clients).
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| samples/storybook/host/src/ForceRemount.stories.tsx | Adds a Storybook reproduction/regression story that forces a subtree remount. |
| samples/storybook/host/src/ForceRemountLocalStorageClient.stories.tsx | Same forced-remount regression story, but using the LocalStorage LD client. |
| packages/launch-darkly/src/EditableLaunchDarklyClient.ts | Extends the editable client contract with resetTransaction() and documents the rationale. |
| packages/launch-darkly/src/InMemoryLaunchDarklyClient.ts | Implements resetTransaction() by undoing an active transaction. |
| packages/launch-darkly/src/LocalStorageLaunchDarklyClient.ts | Implements resetTransaction() by undoing an active transaction. |
| packages/firefly-storybook/src/withFeatureFlagsOverrideDecorator.tsx | Calls resetTransaction() before startTransaction() to avoid the remount race; guards cleanup. |
| .mcp.json | Adds MCP server configuration for chrome-devtools. |
…or.tsx Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
…add regression tests
Alexandre Asselin (alexasselin008)
approved these changes
Apr 3, 2026
Patrick Lafrance (patricklafrance)
merged commit d2a0d22
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Fix issue #571