feat(lint/css): add noHexColors

[dyc3]

Summary

Port https://stylelint.io/user-guide/rules/color-no-hex/

Generated by gpt-5.2-codex

Test Plan

snapshots

Docs

[changeset-bot]

🦋 Changeset detected

Latest commit: 7c19ff3

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

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[coderabbitai]

Walkthrough

A new CSS linter rule noHexColors was added to the nursery rules. The rule detects hexadecimal colour literals in CSS and reports them, recommending named colours or colour functions (rgb/rgba/hsl/hsla/oklch). Changes include the rule implementation, a NoHexColorsOptions options type, tests for valid and invalid cases, a changeset entry, and documentation/metadata tying the rule to Stylelint's color-no-hex.

Possibly related PRs

• fix(migrate): fix migrate command not picking up rules for css, graphql, html #8863 — Adds registry/migration support that would pick up newly added analyzer rules such as biome_css_analyze::no_hex_colors.

Suggested reviewers

• ematipico

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding a new CSS linter rule named noHexColors to Biome.
Description check	✅ Passed	The description is related to the changeset, explaining the motivation (porting a Stylelint rule) and test approach, though it could be more detailed.

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✨ Finishing touches

• 📝 Generate docstrings

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In @.changeset/quiet-hounds-shout.md:
- Line 5: Add a short inline "invalid example" to the changeset entry for the
new nursery rule noHexColors by inserting a concise code snippet that
demonstrates a hex color being flagged (for example a CSS declaration like
color: `#ff0000`;), so the changeset includes a clear invalid example for the
linter; update .changeset/quiet-hounds-shout.md near the rule description to
include this single-line invalid snippet.

[coderabbitai]

⚠️ Potential issue | 🟡 Minor

Please add an invalid example to the changeset.

A short inline snippet is required for new lint rules in changesets. Based on learnings, please include one.

✍️ Suggested tweak

-Added the nursery rule [`noHexColors`](https://biomejs.dev/linter/rules/no-hex-colors/), which flags the use of hexadecimal color codes in CSS and suggests using named colors or RGB/RGBA/HSL/HSLA formats instead.
+Added the nursery rule [`noHexColors`](https://biomejs.dev/linter/rules/no-hex-colors/), which flags the use of hexadecimal color codes in CSS and suggests using named colors or RGB/RGBA/HSL/HSLA formats instead. Example (invalid): `a { color: `#000`; }`

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	Added the nursery rule [`noHexColors`](https://biomejs.dev/linter/rules/no-hex-colors/), which flags the use of hexadecimal color codes in CSS and suggests using named colors or RGB/RGBA/HSL/HSLA formats instead.
	Added the nursery rule [`noHexColors`](https://biomejs.dev/linter/rules/no-hex-colors/), which flags the use of hexadecimal color codes in CSS and suggests using named colors or RGB/RGBA/HSL/HSLA formats instead. Example (invalid): `a { color: `#000`; }`

🤖 Prompt for AI Agents

In @.changeset/quiet-hounds-shout.md at line 5, Add a short inline "invalid
example" to the changeset entry for the new nursery rule noHexColors by
inserting a concise code snippet that demonstrates a hex color being flagged
(for example a CSS declaration like color: `#ff0000`;), so the changeset includes
a clear invalid example for the linter; update .changeset/quiet-hounds-shout.md
near the rule description to include this single-line invalid snippet.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will degrade performance by 16.25%

_{Comparing dyc3/no-hex-colors (7c19ff3) with main (f924f23)}

Summary

❌ 4 regressed benchmarks
✅ 25 untouched benchmarks
⏩ 126 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	css_analyzer[bootstrap_18416142857265205439.css]	515.5 ms	573.8 ms	-10.15%
❌	css_analyzer[tachyons_11778168428173736564.css]	140.9 ms	167.3 ms	-15.76%
❌	css_analyzer[foundation_11602414662825430680.css]	191.4 ms	228.5 ms	-16.25%
❌	css_analyzer[pure_9395922602181450299.css]	20.2 ms	22.1 ms	-8.53%

Footnotes

1. 126 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. ↩