fix: allow additional properties in CSSLanguageOptions

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

AI acknowledgment

• I did not use AI to generate this PR.
• (If the above is not checked) I have reviewed the AI-generated content before submitting.

What is the purpose of this pull request?

While eslint/eslint#19615 (comment) determined that XXXLanguageOptions can have additional properties, and MarkdownLanguageOptions already extends the LanguageOptions type from @eslint/core, the corresponding CSSLanguageOptions does not allow additional properties.

What changes did you make? (Give an overview)

So, I’ve updated CSSLanguageOptions to extend LanguageOptions from @eslint/core and added type test cases to verify that it allows additional properties.

Just a note: CSSLanguageOptions was already being exported from the main entry point, so this PR doesn’t introduce a new feature and only includes a fix.

Related Issues

• Change Request: allow unknown properties in languageOptions eslint#19615 (comment)
• https://github.com/eslint/markdown/blob/main/src/types.ts#L136-L151
• fix: allow additional properties in JSONLanguageOptions json#271

Is there anything you'd like reviewers to focus on?

I found it while working on eslint/markdown#706.

Summary by CodeRabbit

• Documentation

  • Improved TypeScript definitions for CSS language configuration options.
  • Added clearer typing for custom syntax configuration and syntax extension callbacks.
  • Clarified support for tolerant parsing and default syntax configuration.

• Tests

  • Expanded type coverage for valid and invalid CSS language options, custom syntax settings, tolerant parsing, and property syntax validation.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: a0943b8d-3a31-4f19-ab5f-438c98a131ee

📥 Commits

Reviewing files that changed from the base of the PR and between 0658aa0 and e5232d6.

📒 Files selected for processing (4)

• src/languages/css-language.js
• src/languages/css-source-code.js
• src/types.ts
• tests/types/types.test.ts

Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review.

---

📝 Walkthrough

Walkthrough

The change moves CSS language option types into src/types.ts, updates CSS modules to import them from that module, and adds compile-time tests for language options and syntax extension types.

Changes

CSS type definitions

Layer / File(s)	Summary
Shared CSS type contract src/types.ts	The module exports DefaultSyntaxConfig and SyntaxExtensionCallback. It defines CSSLanguageOptions with tolerant and customSyntax properties.
Type consumers and validation src/languages/css-language.js, src/languages/css-source-code.js, tests/types/types.test.ts	CSS language modules use the shared CSSLanguageOptions type. Type tests cover valid and invalid language options, syntax configurations, and extension callbacks.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: pixel998

Merge Risk: ⚪ Minimal · up to e5232

The relocated CSS type contract remains publicly available and is covered by package-facing compile-time assertions, with no actionable merge risk identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: allowing additional properties in CSSLanguageOptions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 4…
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 docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/allow-additional-properties-in-csslanguageoptions

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

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

[lumirlumir]

These three types, which were previously inlined, have already been exported from the main entry point by the following code. Exporting them here does not introduce any new type exports.

css/src/index.js

Line 42 in 0658aa0

export * from "./languages/css-language.js";

[DMartens]

Changes LGTM, thanks. Leaving open for others to review.