feat(css): add support for @debug, @warn, and @error SCSS at-rules

[denbezrukov]

Summary

Adds initial support for SCSS-specific statement at-rules: @debug, @warn, and @error.

Test Plan

• Added parser coverage for valid and invalid SCSS @debug, @warn, and @error cases
• Added formatter coverage for SCSS @debug / @warn / @error

[changeset-bot]

⚠️ No Changeset found

Latest commit: 0b77f91

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	53009	53009	0
Passed	51789	51789	0
Failed	1178	1178	0
Panics	42	42	0
Coverage	97.70%	97.70%	0.00%

jsx/babel

Test result	main count	This PR count	Difference
Total	38	38	0
Passed	37	37	0
Failed	1	1	0
Panics	0	0	0
Coverage	97.37%	97.37%	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	5466	5466	0
Passed	1915	1915	0
Failed	3551	3551	0
Panics	0	0	0
Coverage	35.03%	35.03%	0.00%

ts/babel

Test result	main count	This PR count	Difference
Total	636	636	0
Passed	568	568	0
Failed	68	68	0
Panics	0	0	0
Coverage	89.31%	89.31%	0.00%

ts/microsoft

Test result	main count	This PR count	Difference
Total	18875	18875	0
Passed	13014	13014	0
Failed	5860	5860	0
Panics	1	1	0
Coverage	68.95%	68.95%	0.00%

[codspeed-hq]

Merging this PR will not alter performance

✅ 58 untouched benchmarks
⏩ 156 skipped benchmarks¹

---

_{Comparing db/scss-at-rule-1 (0b77f91) with main (0536fd3)}

Footnotes

1. 156 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. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: f50f572f-ee8d-47ea-a1d8-737f972d6d85

📥 Commits

Reviewing files that changed from the base of the PR and between 79f0e86 and 0b77f91.

📒 Files selected for processing (1)

• crates/biome_css_parser/src/syntax/at_rule/mod.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• crates/biome_css_parser/src/syntax/at_rule/mod.rs

---

Walkthrough

Adds full SCSS @debug, @warn and @error support across the codebase: lexer keyword tokens, parsing helpers and a shared expression-at-rule parser, AST/grammar additions, formatter implementations and wiring, codegen updates, and test cases (both ok and error suites). Also adds a SyntaxFeature helper method used for conditional parsing.

Suggested labels

L-SCSS

Suggested reviewers

• ematipico
• siketyan

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately reflects the main change: adding support for three SCSS at-rules (@debug, @warn, @error).
Description check	✅ Passed	The description is directly related to the changeset, clearly stating the addition of SCSS at-rule support with test coverage details.

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

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch db/scss-at-rule-1

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

crates/biome_css_parser/src/syntax/parse_error.rs (1)

185-213: ⚠️ Potential issue | 🟡 Minor

Gate SCSS-only at-rule suggestions by file type.

expected_any_at_rule() feeds generic at-rule diagnostics, so adding "debug", "warn", and "error" unconditionally will now tell plain .css users those names are expected too. Please only include them when the parser is in SCSS mode; otherwise the hint becomes a bit cheeky and a bit wrong.

🤖 Prompt for AI Agents

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

In `@crates/biome_css_parser/src/syntax/parse_error.rs` around lines 185 - 213,
The current expected_any_at_rule function always includes SCSS-only at-rules
("debug", "warn", "error"); update it to conditionally include those three names
only when the parser is in SCSS mode: inside expected_any_at_rule (referencing
CssParser p) build the list of at-rule names into a mutable Vec<&str>, push the
SCSS-only strings only if p indicates SCSS mode (call the parser's SCSS-checking
accessor such as p.is_scss() or p.syntax.is_scss()), then pass that Vec (or
slice) to expect_one_of(...) and .into_diagnostic(p) so plain .css parsing does
not get SCSS-specific suggestions.

🤖 Prompt for all review comments with AI agents

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

Outside diff comments:
In `@crates/biome_css_parser/src/syntax/parse_error.rs`:
- Around line 185-213: The current expected_any_at_rule function always includes
SCSS-only at-rules ("debug", "warn", "error"); update it to conditionally
include those three names only when the parser is in SCSS mode: inside
expected_any_at_rule (referencing CssParser p) build the list of at-rule names
into a mutable Vec<&str>, push the SCSS-only strings only if p indicates SCSS
mode (call the parser's SCSS-checking accessor such as p.is_scss() or
p.syntax.is_scss()), then pass that Vec (or slice) to expect_one_of(...) and
.into_diagnostic(p) so plain .css parsing does not get SCSS-specific
suggestions.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 4bdd68f7-7a8d-45c3-9a40-bf741c58b06c

📥 Commits

Reviewing files that changed from the base of the PR and between 0536fd3 and 79f0e86.

⛔ Files ignored due to path filters (13)

• 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/css/scss/at-rule/debug-warn-error.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/debug.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/error.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/warn.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/debug.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/error.scss.snap is excluded by !**/*.snap and included by **
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/warn.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 (27)

• crates/biome_css_formatter/src/css/any/at_rule.rs
• crates/biome_css_formatter/src/generated.rs
• crates/biome_css_formatter/src/scss/mod.rs
• crates/biome_css_formatter/src/scss/statements/debug_at_rule.rs
• crates/biome_css_formatter/src/scss/statements/error_at_rule.rs
• crates/biome_css_formatter/src/scss/statements/mod.rs
• crates/biome_css_formatter/src/scss/statements/warn_at_rule.rs
• crates/biome_css_formatter/tests/specs/css/scss/at-rule/debug-warn-error.scss
• crates/biome_css_parser/src/lexer/mod.rs
• crates/biome_css_parser/src/lexer/tests.rs
• crates/biome_css_parser/src/syntax/at_rule/mod.rs
• crates/biome_css_parser/src/syntax/parse_error.rs
• crates/biome_css_parser/src/syntax/scss/at_rule/debug.rs
• crates/biome_css_parser/src/syntax/scss/at_rule/error.rs
• crates/biome_css_parser/src/syntax/scss/at_rule/mod.rs
• crates/biome_css_parser/src/syntax/scss/at_rule/warn.rs
• crates/biome_css_parser/src/syntax/scss/mod.rs
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/debug.scss
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/error.scss
• crates/biome_css_parser/tests/css_test_suite/error/scss/at-rule/warn.scss
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/debug.scss
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/error.scss
• crates/biome_css_parser/tests/css_test_suite/ok/scss/at-rule/warn.scss
• crates/biome_grit_patterns/src/grit_target_language/css_target_language/generated_mappings.rs
• crates/biome_parser/src/lib.rs
• xtask/codegen/css.ungram
• xtask/codegen/src/css_kinds_src.rs