[denbezrukov]

This PR was developed with assistance from OpenAI Codex.

Summary

Adds parser and formatter support for expression-based SCSS @at-root queries.

@use "sass:list";
@use "sass:map";

$query: "without: rule";
$rules: media supports;

@at-root ($query) {
  .overlay {
    position: fixed;
  }
}

@at-root (without: $rules) {
  .rules {
    color: red;
  }
}

@at-root ("with" + "out": media) {
  .quoted {
    color: blue;
  }
}

@at-root (
  map.get((mode: without), mode):
    list.join(media, supports)
) {
  .computed {
    display: block;
  }
}

Test Plan

• cargo test -p biome_css_parser
• cargo test -p biome_css_formatter

[agentscanapp]

A maintainer will take a look as soon as they can. In the meantime, please make sure that:

• the description follows our PR template
• any related issues are linked
• existing tests still pass

[changeset-bot]

⚠️ No Changeset found

Latest commit: 214f070

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.

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[github-actions]

Parser conformance results on

js/262

Test result	main count	This PR count	Difference
Total	49797	49797	0
Passed	48773	48773	0
Failed	1024	1024	0
Panics	0	0	0
Coverage	97.94%	97.94%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	40	40	0
Passed	37	37	0
Failed	3	3	0
Panics	0	0	0
Coverage	92.50%	92.50%	0.00%

markdown/commonmark

Test result	main count	This PR count	Difference
Total	652	652	0
Passed	652	652	0
Failed	0	0	0
Panics	0	0	0
Coverage	100.00%	100.00%	0.00%

symbols/microsoft

Test result	main count	This PR count	Difference
Total	6322	6322	0
Passed	2147	2147	0
Failed	4175	4175	0
Panics	0	0	0
Coverage	33.96%	33.96%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	662	662	0
Passed	592	592	0
Failed	70	70	0
Panics	0	0	0
Coverage	89.43%	89.43%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	17646	17646	0
Passed	13449	13449	0
Failed	4197	4197	0
Panics	0	0	0
Coverage	76.22%	76.22%	0.00%

yaml/yaml-test-suite

Test result	main count	This PR count	Difference
Total	402	402	0
Passed	402	402	0
Failed	0	0	0
Panics	0	0	0
Coverage	100.00%	100.00%	0.00%

[coderabbitai]

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🧰 Additional context used

📚 Code guidelines (1)

AGENTS.md — auto-discovered

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository: biomejs/biome/.coderabbit.yaml
• Review profile: CHILL
• Plan: Advanced
• Run ID: 118d5fe4-8556-4da4-8f19-fd9235224f57

📥 Commits

Reviewing files that changed from the base of the PR and between 7978e5e and 214f070.

⛔ Files ignored due to path filters (20)

• crates/biome_css_factory/src/generated/node_factory.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_css_factory/src/generated/syntax_factory.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_css_formatter/tests/specs/scss/at-rule/dynamic-at-root-comments.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_formatter/tests/specs/scss/at-rule/dynamic-at-root-layout.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_formatter/tests/specs/scss/at-rule/dynamic-at-root-namespaced.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_formatter/tests/specs/scss/at-rule/dynamic-at-root-suppression.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_formatter/tests/specs/scss/at-rule/dynamic-at-root.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/at-root.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/dynamic-at-root-eof.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/dynamic-at-root-recovery.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/at_rule/dynamic-at-root-unknown.css.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/at-root.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/dynamic-at-root-expressions.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/dynamic-at-root-syntax-only.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/dynamic-at-root.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/valid-modern-sweep.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_syntax/src/generated/kind.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_css_syntax/src/generated/macros.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_css_syntax/src/generated/nodes.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_css_syntax/src/generated/nodes_mut.rs is excluded by !**/generated/**, !**/generated/** and included by **

📒 Files selected for processing (3)

• crates/biome_css_formatter/src/generated.rs
• crates/biome_grit_patterns/src/grit_target_language/css_target_language/generated_mappings.rs
• xtask/codegen/css.ungram

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

---

Walkthrough

The parser now accepts general SCSS expressions and modifier-and-rules clauses in @at-root queries. The formatter supports the revised syntax, including comment placement and suppression handling. Parser and formatter fixtures cover valid queries, malformed input, layouts, comments and namespaced variables.

Suggested reviewers: dyc3

Priority: ⬇️ Low

Change: Feature

Merge Risk: ⚪ Minimal · up to 214f0

This change broadens SCSS @at-root query parsing and formatting. Malformed empty clauses still report errors and recover, and the supplied evidence shows no actionable merge-readiness risk.

Architecture Summary

Architecture risk: 🔵 Low · up to 214f0

The change affects 2 systems.

Changed systems: crates, xtask

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — crates (service) was modified; 23 changed files map to changed impact.
• observed — xtask (service) was modified; 2 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in crates/biome_css_formatter/src/comments.rs: The syntax imports add ScssAtRootQueryClause.
• observed — Modified behavior in crates/biome_css_formatter/src/comments.rs: The comment-placement chain now tries handle_scss_at_root_query_comment after the SCSS expression-item trailing-line-comment handler and before the at-root selector handler.
• observed — Modified behavior in crates/biome_css_formatter/src/comments.rs: Adds handle_scss_at_root_query_comment. It finds an enclosing ScssAtRootQueryClause, requires both its colon token and rules node, and attaches the comment as dangling to the clause only when the comment’s text range falls between the trimmed colon and rules boundaries; missing syntax elements or comments outside that range retain default placement.
• observed — Modified behavior in crates/biome_css_formatter/src/scss/any/at_root_query.rs: Added the FormatAnyScssAtRootQuery rule, which formats either supported query variant by delegating to that node’s formatter.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: support for expression-based SCSS @at-root queries.
Description check	✅ Passed	The description explains the parser and formatter changes, gives relevant SCSS examples, and lists the planned tests.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Commit to this branch
• Create a new PR

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[codspeed]

Merging this PR will not alter performance

⚠️ 3 benchmarks measured no execution time

Nothing ran under measurement, usually because the compiler removed the code under test. These results are not comparable, so they count as unchanged.

Preventing compiler optimizations

✅ 114 untouched benchmarks
⏩ 299 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚠️	grit_query_anchor_kinds[code_snippet]	< 1 ns	< 1 ns	N/A
⚠️	grit_query_anchor_kinds[metavariable]	< 1 ns	< 1 ns	N/A
⚠️	grit_query_anchor_kinds[or_pattern]	< 1 ns	< 1 ns	N/A

---

_{Comparing dbezrukov/scss-dynamic-at-root-queries (214f070) with main (4db3f58)}

Footnotes

1. 299 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. ↩