fix(noUselessEscapeInString): correctly flag chars by ematipico · Pull Request #9420 · biomejs/biome

ematipico · 2026-03-09T16:58:12Z

Summary

Closes #9385

Test Plan

Added a test and updated the current ones

Docs

N/A

changeset-bot · 2026-03-09T16:58:17Z

🦋 Changeset detected

Latest commit: 3abcf8a

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 · 2026-03-09T17:03:10Z

Walkthrough

This patch fixes the noUselessEscapeInString rule in the CSS linter, which was incorrectly flagging valid CSS hexadecimal escape sequences as useless. The rule now correctly recognises hex digits (0–9, a–f, A–F) as valid escape sequences within CSS strings. Core logic has been updated to include these hex values alongside existing valid escapes, whilst test cases have been updated to reflect the corrected behaviour. This resolves false positives when using Unicode escapes in CSS content properties, particularly for icon fonts.

Suggested labels

A-Linter, L-CSS

Suggested reviewers

denbezrukov
siketyan

🚥 Pre-merge checks | ✅ 3 | ❌ 1

❌ Failed checks (1 inconclusive)

Check name	Status	Explanation	Resolution
Title check	❓ Inconclusive	The title 'fix(noUselessEscapeInString): correctly flag chars' is somewhat vague and incomplete—'correctly flag chars' lacks clarity about which characters or what the actual fix accomplishes.	Consider a more descriptive title like 'fix(noUselessEscapeInString): preserve valid CSS hex escapes' to clearly indicate the fix handles hex escapes in CSS strings.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description check	✅ Passed	The PR description mentions closing issue `#9385` and describes adding/updating tests, which aligns with the changeset focused on fixing Unicode escape handling in CSS content properties.
Linked Issues check	✅ Passed	The PR addresses the core requirement from `#9385` by modifying noUselessEscapeInString to accept valid CSS hex escapes (0-9, a-f, A-F), preventing false positives on sequences like \e7bb used in icon fonts.
Out of Scope Changes check	✅ Passed	All changes are scoped to the noUselessEscapeInString rule and its tests; no unrelated modifications to other linting rules or unrelated features.

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🧪 Generate unit tests (beta)

Create PR with unit tests
Post copyable unit tests in a comment
Commit unit tests in branch fix/css-fix-parser

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coderabbitai

Actionable comments posted: 1

🧹 Nitpick comments (1)

crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/valid.css (1)
10-12: Consider one uppercase or digit-led fixture too.

This proves the lowercase path, but the matcher now also allows 0-9 and A-F. Adding one \31 or \E7BB example would keep those branches from quietly wandering off later.
🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In
`@crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/valid.css`
around lines 10 - 12, Add an additional test fixture to cover the digit-led or
uppercase hex-escape branches: alongside the existing .icon-file:before {
content: "\e7bb"; } add another rule using either a digit-led escape (e.g.,
content: "\31";) or an uppercase hex escape (e.g., content: "\E7BB";) so the
matcher is exercised for `0-9` and `A-F` paths.

🤖 Prompt for all review comments with AI agents

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

Inline comments:
In
`@crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/invalid.css`:
- Line 4: The test CSS contains inline comments without inner whitespace around
the comment text (the line with content: /*before*/ "useless \z" /*after*/),
which trips stylelint's comment-whitespace-inside; update the test string to add
spaces inside those comments (e.g., change /*before*/ to /* before */ and
/*after*/ to /* after */) so it conforms to comment-whitespace-inside, then
refresh the snapshot; if the test intentionally ignores inner spacing,
alternatively update the test's expected snapshot to match the exact current
spacing.

---

Nitpick comments:
In
`@crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/valid.css`:
- Around line 10-12: Add an additional test fixture to cover the digit-led or
uppercase hex-escape branches: alongside the existing .icon-file:before {
content: "\e7bb"; } add another rule using either a digit-led escape (e.g.,
content: "\31";) or an uppercase hex escape (e.g., content: "\E7BB";) so the
matcher is exercised for `0-9` and `A-F` paths.

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 87b103bd-b52b-425d-b702-72157a9ec55a

📥 Commits

Reviewing files that changed from the base of the PR and between 744fe78 and 3abcf8a.

⛔ Files ignored due to path filters (2)

crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/invalid.css.snap is excluded by !**/*.snap and included by **
crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/valid.css.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (4)

.changeset/fix-css-unicode-escape-in-string.md
crates/biome_css_analyze/src/lint/suspicious/no_useless_escape_in_string.rs
crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/invalid.css
crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/valid.css

coderabbitai · 2026-03-09T17:03:13Z

+
 .a::after {
-    content: /*before*/ "useless \a" /*after*/
+    content: /*before*/ "useless \z" /*after*/


⚠️ Potential issue | 🟡 Minor

Stylelint will trip on the inline comments.

Line 4 violates comment-whitespace-inside because of /*before*/ and /*after*/. If the exact spacing is not part of the range test, add the inner spaces and refresh the snapshot.

🧰 Tools

🪛 Stylelint (17.4.0)

[error] 4-4: Expected whitespace after "/*" (comment-whitespace-inside)

(comment-whitespace-inside)

[error] 4-4: Expected whitespace before "*/" (comment-whitespace-inside)

(comment-whitespace-inside)

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed. In `@crates/biome_css_analyze/tests/specs/suspicious/noUselessEscapeInString/invalid.css` at line 4, The test CSS contains inline comments without inner whitespace around the comment text (the line with content: /*before*/ "useless \z" /*after*/), which trips stylelint's comment-whitespace-inside; update the test string to add spaces inside those comments (e.g., change /*before*/ to /* before */ and /*after*/ to /* after */) so it conforms to comment-whitespace-inside, then refresh the snapshot; if the test intentionally ignores inner spacing, alternatively update the test's expected snapshot to match the exact current spacing.

codspeed-hq · 2026-03-09T17:07:41Z

Merging this PR will not alter performance

✅ 29 untouched benchmarks
⏩ 187 skipped benchmarks¹

_{Comparing fix/css-fix-parser (3abcf8a) with main (744fe78)²}

187 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. ↩
No successful run was found on main (5978824) during the generation of this report, so 744fe78 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

fix(noUselessEscapeInString): correctly flag chars

3abcf8a

ematipico requested review from a team March 9, 2026 16:58

github-actions Bot added A-Linter Area: linter L-CSS Language: CSS and super languages labels Mar 9, 2026

coderabbitai Bot reviewed Mar 9, 2026

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Netail approved these changes Mar 9, 2026

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ematipico merged commit a1c46af into main Mar 9, 2026
18 checks passed

ematipico deleted the fix/css-fix-parser branch March 9, 2026 18:09

github-actions Bot mentioned this pull request Mar 9, 2026

ci: release #9346

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fix(noUselessEscapeInString): correctly flag chars#9420

fix(noUselessEscapeInString): correctly flag chars#9420
ematipico merged 1 commit intomainfrom
fix/css-fix-parser

ematipico commented Mar 9, 2026

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coderabbitai Bot commented Mar 9, 2026

❌ Failed checks (1 inconclusive)

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ematipico commented Mar 9, 2026

Summary

Test Plan

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changeset-bot Bot commented Mar 9, 2026

🦋 Changeset detected

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coderabbitai Bot commented Mar 9, 2026

Walkthrough

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codspeed-hq Bot commented Mar 9, 2026

Merging this PR will not alter performance

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