Do not hook assetEmitted when writeToDisk is true#2277
Merged
alexander-akait merged 1 commit intowebpack:mainfrom Mar 10, 2026
Merged
Do not hook assetEmitted when writeToDisk is true#2277alexander-akait merged 1 commit intowebpack:mainfrom
alexander-akait merged 1 commit intowebpack:mainfrom
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When `writeToDisk: true`, `setupOutputFileSystem` already configures webpack to use the native (disk) output file system, so webpack writes all assets to disk itself. Calling `setupWriteToDisk` on top of that tapped `assetEmitted` and wrote every file a second time. Only invoke `setupWriteToDisk` when `writeToDisk` is a filter function, where the in-memory fs is still used and selective disk writes are needed. Fixes webpack#2270
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This closes #2270 |
alexander-akait
approved these changes
Mar 10, 2026
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #2277 +/- ##
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Coverage 95.88% 95.88%
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Files 13 13
Lines 900 900
Branches 270 270
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Hits 863 863
Misses 37 37 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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Summary
When
writeToDisk: trueis set, files were being written to disk twice — once by webpack via its native output file system (configured bysetupOutputFileSystem), and again by theassetEmittedhook set up insetupWriteToDisk. This caused redundant I/O for every emitted asset.The fix changes the call site in
index.jsto only invokesetupWriteToDiskwhenwriteToDiskis a filter function. When it istrue, webpack handles disk writes natively and no hook is needed.What kind of change does this PR introduce?
fix
Did you add tests for your changes?
Yes. The existing
writeToDisk: truetests inmiddleware.test.jsalready asserted on the number ofassetEmittedtaps — those assertions have been updated fromtoHaveLength(1)totoHaveLength(0)to reflect thatDevMiddlewareno longer tapsassetEmittedwhenwriteToDisk: true. The tests continue to verify that the bundle file is found on disk.Does this PR introduce a breaking change?
No. Behaviour for end users is unchanged — files are still written to disk when
writeToDisk: true, just without the redundant second write.If relevant, what needs to be documented once your changes are merged or what have you already documented?
No documentation changes needed.
Use of AI
This PR was developed with the assistance of Claude (Anthropic). The fix and tests were generated and reviewed with AI support, in accordance with the webpack AI policy.