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build(tooling): close the reference parsers' gaps in the parser-agreement column - #22937
Follow-up to #22907. Every disagreement the new column reported in the corpora came from a gap in the comparison, not from a webpack bug, so this closes those gaps. A "no" in the column now points at something real.
css-tree: inside a style rule it gives up once declarations and nested rules mix, and it reads a nested at-rule's block as rules only. Both are re-read, declarations first.
IE hacks: a declaration whose name doesn't start with an identifier (*zoom) is dropped, as the spec drops it. postcss's _prop hack is read back as written.
webpack (CSS): block contents are compared in source order. webpack's walk visits declarations before nested rules by design (consumeABlocksContents), and the printer keeps source order.
parse5: a <?… cut off at the end of the input is dropped where webpack's processing-instruction rules drop it (_scanProcessingInstruction).
Cells: when both sides are longer than the cut, both are shown from just before the first differing character. This exposed one real disagreement: htmlparser2 (xmlMode) keeps a newline inside an attribute value, which XML attribute-value normalization turns into a space.
before
after
CSS corpus (77): webpack / postcss disagree
4 / 5
0 / 0
test/**/*.css (1034): webpack disagrees
32
12 (invalid-CSS recovery cases where css-tree's recovery differs from the spec's)
test/**/*.html (406): webpack disagrees
4
3 (parse5 has no declarative shadow root or customizable <select>)
What kind of change does this PR introduce?
build
Did you add tests for your changes?
Yes: test/unitCases/tooling/compare-{css,html,harness}.unittest.js. The new HTML cases fail against main's reader.
Does this PR introduce a breaking change?
No.
If relevant, what needs to be documented once your changes are merged or what have you already documented?
Updated in tooling/COMPARE_TOOLS.md.
Use of AI
Written with Claude Code: it traced each disagreement to its cause, wrote the code, tests and docs, and ran lint and the targeted tests. The requester directed the work and reviews it.
…ment column
Re-read what css-tree gives up on inside a style rule, drop declarations the
spec drops, compare webpack's CSS blocks in source order, mirror webpack's
processing instruction rules in parse5's tree, and cut both sides of a cell
at the first character they differ at.
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Reviewing files that changed from the base of the PR and between 808a9c8 and 99f48b0.
Files selected for processing: 4
test/unitCases/tooling/compare-css.unittest.js
test/unitCases/tooling/compare-html.unittest.js
tooling/compare-css-tools.js
tooling/compare-html-tools.js
Files skipped from review as they are similar to previous changes: 2
test/unitCases/tooling/compare-css.unittest.js
test/unitCases/tooling/compare-html.unittest.js
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Walkthrough
The parser-agreement tooling now reparses selected CSS fragments, filters declaration names, and orders webpack CSS events by source position. It also adjusts parse5 handling of selected incomplete processing instructions and shows nearby context for long tree differences.
Changes: Parser comparison tooling
Layer / File(s)
Summary
CSS fragment and declaration comparison tooling/compare-css-tools.js, test/unitCases/tooling/compare-css.unittest.js, tooling/COMPARE_TOOLS.md
The CSS readers filter declaration names and handle selected raw CSS fragments through reparsing. PostCSS declaration names include leading raw text. Tests cover nested content, unparsed fragments, and unusual property names. The documentation describes these adjustments and remaining parser differences.
The webpack CSS reader stores rule, at-rule, and declaration events in held nodes, then emits them in source order.
Incomplete HTML processing instructions tooling/compare-html-tools.js, test/unitCases/tooling/compare-html.unittest.js
The parse5 comparison reader uses source locations and omits selected trailing incomplete processing-instruction comments. Tests cover incomplete targets and instructions, as well as a closed comment.
The formatter compares full event descriptions before shortening the displayed context. The test covers long values that differ near the end.
Suggested labels:area: tooling
Priority: Low
Change: Bug fix
Merge Risk: Minimal · up to 99f48
No actionable merge-blocking risk is established by this change.
Pre-merge checks: 3 · 1
Failed checks: 1 inconclusive
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The title uses valid Conventional Commit syntax with type build, scope tooling, and a subject that accurately describes the parser-agreement changes. The branch prefix is not provided, so the type…
Provide the branch name or confirm that its prefix is build.
Passed checks: 3 passed
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The title uses valid Conventional Commit syntax with type build, scope tooling, and a subject that accurately describes the parser-agreement changes. The branch prefix is not provided, so the type-to-branch-prefix requirement cannot be verified.
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Actionable comments posted: 3
🪄 Fix comments: Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @tooling/compare-css-tools.js:
- Line 1003: Update the property-name construction that combines
node.raws.before with node.prop to discard stray PostCSS hack characters such as
semicolons while preserving the actual property name, so valid declarations like
top remain included in the comparison.
Review comments at @tooling/compare-html-tools.js:
- Line 973: Update the comment check using source.endsWith so it identifies the
EOF comment from its source-position metadata, then classifies the corresponding
raw source text rather than matching normalized comment data; preserve completed
comments earlier in the document even when their text matches the script ending.
- Line 941: Update the target-matching logic in droppedAtEnd so the target
capture recognizes newline delimiters and uses webpack’s ASCII whitespace set
instead of \s; preserve the reserved-target behavior for delimiters at EOF.
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Comparing base (cc6858e) to head (99f48b0). Merging this pull request will not change the code webpack generates.
What moved
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Read Changed, test untouched first: the test is byte-identical on both sides, so webpack generated the difference. Changed, test edited moved partly because the test did — Test edit is how many bytes the test gained, and a bundle that grew by less is not a regression. New and Deleted are whole files, not deltas — a new asset was created, not grown, so it reads gray (⚪ added) — and adding tests cannot bury a real change. Gzip decides, because that is what users download; raw is the tiebreak, and brotli and zstd are per asset below.
No asset changed size.
No runtime gained or lost a runtime module.
Built test/configCases with the defaults a user gets: 2307 test(s), 9360 asset(s), 103 emitted nothing.
System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.
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Summary
Follow-up to #22907. Every disagreement the new column reported in the corpora came from a gap in the comparison, not from a webpack bug, so this closes those gaps. A "no" in the column now points at something real.
*zoom) is dropped, as the spec drops it. postcss's_prophack is read back as written.consumeABlocksContents), and the printer keeps source order.<?…cut off at the end of the input is dropped where webpack's processing-instruction rules drop it (_scanProcessingInstruction).test/**/*.css(1034): webpack disagreestest/**/*.html(406): webpack disagrees<select>)What kind of change does this PR introduce?
build
Did you add tests for your changes?
Yes:
test/unitCases/tooling/compare-{css,html,harness}.unittest.js. The new HTML cases fail againstmain's reader.Does this PR introduce a breaking change?
No.
If relevant, what needs to be documented once your changes are merged or what have you already documented?
Updated in
tooling/COMPARE_TOOLS.md.Use of AI
Written with Claude Code: it traced each disagreement to its cause, wrote the code, tests and docs, and ran lint and the targeted tests. The requester directed the work and reviews it.
Generated by Claude Code
Summary by CodeRabbit