webpack
Unused assets left by code optimization
Bug Description
When using code optimization to drop unused code, assets that were emitted but no longer referenced are still emitted.
Link to Minimal Reproduction and step to reproduce
https://github.com/MattIPv4/webpack-asset-repro
-
npm ci -
npm run build -
ls dist/*.png - for each
file.png,cat dist/main.js | grep <file.png>
One png should be referenced in dist/main.js, while the other won't be as it was used by dead code.
Expected Behavior
Assets that are emitted but later made unused by code optimization should be removed from the emitted assets
Actual Behavior
Assets are always emitted even if all references to them are dropped by code optimization
Environment
System:
OS: macOS 26.1
CPU: (14) arm64 Apple M4 Pro
Memory: 97.52 MB / 24.00 GB
Binaries:
Node: 22.13.1 - /Users/mattcowley/.local/state/fnm_multishells/85154_1765079840717/bin/node
npm: 10.9.2 - /Users/mattcowley/.local/state/fnm_multishells/85154_1765079840717/bin/npm
pnpm: 10.20.0 - /Users/mattcowley/.local/state/fnm_multishells/85154_1765079840717/bin/pnpm
Browsers:
Chrome: 142.0.7444.177
Firefox Developer Edition: 146.0
Safari: 26.1
Safari Technology Preview: 26.0
Packages:
webpack-cli: ^6.0.1 => 6.0.1
Is this a regression?
None
Last Working Version
No response
Additional Context
No response
You need to add the following line to your package.json file. See more: optimization.sideEffects
+ "sideEffects": false
That worked! ...but I don't understand why? If the import of the image were to be seen as a side effect, why isn't the import itself left in place? All that gets left is a completely unreferenced image asset?
Hm... in the real world it doesn't seem to work though... https://github.com/alveusgg/extension/pull/401 if I pnpm build here, ls build/static/media/ambassadors/*/emote*.png still returns files generated even though they're unused.