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fix(css): read an rgb() separator grammar before folding it - #22251
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`_minifyColorFunction` cuts on whitespace, `,` and `/` in one pass without recording which separator stood where, so every spelling collapsed to the same argument list: `rgb(1, 2 3)`, `rgb(1 2, 3)`, `rgb(1 2 3, .5)`, `rgb(1, 2, 3 / .5)`, `rgb(1 2 3 .5)` and `rgb(1 / 2 / 3)` all folded to a color. Each is a declaration an engine drops, so folding it changed what rendered. This is the defect #22242 fixed for `hsl()`, `hwb()` and the Lab family, left out of that change because `rgb()` reads its arguments through a scanner of its own. The same two grammars decide it — the modern `A B C` with an optional `/ D`, and the legacy `A, B, C` with an optional `, D`, both of which `rgb()` has — so the check is the pair of regexps that change already added, applied after the scan rather than before it, where only a plausible color reaches it. The pending changeset for #22242 covers this, so it is widened rather than duplicated.
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| Name | Type |
|---|---|
| webpack | Patch |
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Repository: webpack/webpack/.coderabbit.yaml Review profile: CHILL Plan: Advanced Run ID: 📒 Files selected for processing (1)
Included review availability: Your plan provides up to 10 included reviews per hour; 3 remain after this review. 📝 WalkthroughWalkthroughChangesThe CSS color minifier now validates RGB and RGBA argument grammar before folding. Mixed separators remain unchanged. The syntax-printer test now verifies installed phases against CSS color grammar handling
Printer phase validation
Priority: ⬇️ Low Change: Bug fix Merge Risk: ⚪ Minimal · up to The change prevents invalid CSS color folding and improves phase-installation coverage; it is ready to merge with normal checks. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Inline comments:
In @.changeset/037-css-unitless-hsl-hwb-channels.md:
- Line 5: Shorten the changeset sentence to a single imperative sentence of 80
characters or fewer, preserving its intent and capitalization, and ensure it
ends with a period.
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⛔ Files ignored due to path filters (2)
test/configCases/css/minimize-colors/__snapshots__/ConfigCacheTest.snapis excluded by!**/*.snap,!test/**/__snapshots__/**test/configCases/css/minimize-colors/__snapshots__/ConfigTest.snapis excluded by!**/*.snap,!test/**/__snapshots__/**
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.changeset/037-css-unitless-hsl-hwb-channels.mdlib/css/syntax-parser.jstest/configCases/css/minimize-colors/style.css
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The union of the two color fixes ran to 148 characters, where `.changeset/**` asks for one imperative sentence of 80 or fewer. Both facts still fit: the unitless channels that now fold, and the separator grammar that decides whether anything folds at all.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #22251 +/- ##
=======================================
Coverage 95.03% 95.03%
=======================================
Files 762 762
Lines 105728 105730 +2
Branches 32541 32542 +1
=======================================
+ Hits 100480 100482 +2
Misses 5248 5248
Flags with carried forward coverage won't be shown. Click here to find out more. ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Generated code sizeComparing base (
Read No asset with an untouched test changed size — every change below comes with a test this pull request edited. 1 asset(s) changed size, test edited
No runtime gained or lost a runtime module. Built |
`should install onto terser` asserted that under Deno `phases` is empty, because Deno could not import terser's own sources when the test was written. It sometimes can, and then the test fails — it went red once on #22243, a pull request touching only CSS fixtures, and cost a re-run of a 21-minute job to establish it was not that change's doing. Which sources a runtime reaches is the one thing `load` is written to tolerate: it catches any failure and hands back terser's published entry point. So the runtime is the wrong thing to assert. What `load` owes everywhere is that it installed phases this build declares and nothing else, and Node, which always reaches the sources, still owes the whole set — both of which this now states. The fallback path stays covered by behaviour rather than by a hardcoded outcome: every `should mangle exactly as terser does` case compares webpack's `minify` against terser's own, whichever way `load` resolved.
Merging this PR will degrade performance by 38.28%
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| Mode | Benchmark | BASE |
HEAD |
Efficiency | |
|---|---|---|---|---|---|
| ❌ | Memory | unit benchmark "js-parser-unit", source 'lodash-es' |
108.5 KB | 272.5 KB | -60.17% |
| ❌ | Memory | unit benchmark "html-parser-document-unit", process (no visitors) |
706.4 KB | 1,137.2 KB | -37.88% |
| ❌ | Memory | benchmark "many-chunks-commonjs", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}' |
184.3 KB | 288.5 KB | -36.11% |
| ❌ | Simulation | unit benchmark "css-printer-tailwind-unit", minify (flat rules) |
2.4 s | 3.4 s | -28.66% |
| ❌ | Memory | benchmark "many-modules-interop-runtime", scenario '{"name":"mode-production","mode":"production"}', measure 'exec' |
15.5 KB | 19.5 KB | -20.59% |
Tip
Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.
Comparing fix/css-rgb-separator-grammar (aae0cba) with main (e2023b0)
Footnotes
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6 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
Summary
rgb()cuts its arguments on whitespace,,and/without recording which separator stood where, sorgb(1, 2 3),rgb(1 2 3, .5),rgb(1, 2, 3 / .5),rgb(1 2 3 .5)andrgb(1 / 2 / 3)all folded to a color — declarations an engine drops, so folding them changed what rendered. This is what #22242 fixed forhsl(),hwb()and the Lab family;rgb()was left out because it reads its arguments through a scanner of its own, so it now applies the same two grammars that change added.What kind of change does this PR introduce?
fix
Did you add tests for your changes?
Yes — five cases in
test/configCases/css/minimize-colors/style.css(.c01–.c05), covering both valid grammars, each mixed spelling, andrgba().Does this PR introduce a breaking change?
No — only spellings that are invalid CSS stop folding.
If relevant, what needs to be documented once your changes are merged or what have you already documented?
n/a
Use of AI
AI was used: it found the defect while addressing a review comment on #22242, reproduced each spelling against the unmodified parser, wrote the fix and the fixtures, and verified that every valid spelling still folds and
yarn test:invariants:cssreports no findings.Generated by Claude Code
Summary by CodeRabbit
rgb()/rgba()formats.hsl()andhwb()only when separators are valid.rgba()follows the same grammar rules asrgb(), producing consistent and safer output across supported color syntaxes.