perf(lint): optimize noIrregularWhitespace rule

[Jayllyz]

Generated by Opus 4.6 with a plan, manually tested on my locals repos.

Summary

I noticed using the rule profiler (really useful thanks) that this rule was the slowest for me. The initial goal here was to speed up the rule for non-matching files. The performance gain isn't huge, but I think its still worth it, around 10% from what i've tested in debug mode

Test Plan

Unit test + manual test on my repos.

Docs

[changeset-bot]

🦋 Changeset detected

Latest commit: 7e83a65

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[codspeed-hq]

Merging this PR will not alter performance

✅ 58 untouched benchmarks
⏩ 96 skipped benchmarks¹

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_{Comparing Jayllyz:perf/no-irregular-whitespace (7e83a65) with main (b99e7db)}

Footnotes

1. 96 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. ↩

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Walkthrough

Refactors the noIrregularWhitespace lints for CSS and JavaScript. Introduces a central is_irregular_whitespace(char) helper, removes the previous static character set, and adds early-return checks to skip work when no irregular characters are present. CSS handling now accepts a CssSyntaxNode and iterates tokens via syntax.descendants_tokens(Direction::Next); JS processing consolidates leading and trailing trivia scanning. No public API changes.

Suggested reviewers

• ematipico
• dyc3
• chansuke

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: a performance optimisation of the noIrregularWhitespace lint rule.
Description check	✅ Passed	The description is directly related to the changeset, explaining the motivation (rule profiler identified slowness), the approach (optimising for non-matching files), and results (approximately 10% improvement).
Merge Conflict Detection	✅ Passed	✅ No merge conflicts detected when merging into main

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

Verify each finding against the current code and only fix it if needed.


In @.changeset/new-dolls-flow.md:
- Line 5: Fix the typo in the changeset line that reads "Sightly improved
performance of
[`noIrregularWhitespace`](https://biomejs.dev/linter/rules/no-irregular-whitespace/)..."
by changing "Sightly" to "Slightly" so the sentence correctly starts "Slightly
improved performance of `noIrregularWhitespace`...".

[ematipico]

I don't think the rule is slow per se, I believe it's slow because it must look at all the spaces inside a document

[dyc3]

This makes sense. match statements get the compiler to vectorize the comparisons a bit better, ive seen it on compiler explorer before. Regardless, its less code overall which is always a good thing.

Very happy the rule profiler helped find this!

[dyc3]

Just curious @Jayllyz, you mentioned you tested in debug mode. Did you try in release mode? Debug mode makes biome significantly slower.