feat(css): add support for modern CSS properties, pseudo-classes, and pseudo-elements

[willfarrell]

Summary

Added modern CSS keywords to the noUnknownProperty, noUnknownPseudoClass, and noUnknownPseudoElement lint rules so they no longer produce false positives for recently standardized or in-progress CSS features.

New known properties: dynamic-range-limit, overlay, reading-flow, reading-order, scroll-marker-group, scroll-target-group.
New pseudo-elements: ::checkmark, ::column, ::picker, ::picker-icon, ::scroll-button, ::scroll-marker, ::scroll-marker-group.
New pseudo-classes: :active-view-transition-type, :has-slotted, :target-after, :target-before, :target-current.

This PR was written with the assistance of Claude Code.

Test Plan

• Added valid test cases for each new property, pseudo-class, and pseudo-element.
• Updated snapshots with cargo insta accept.

Docs

No external documentation changes needed, the keywords are internal to the existing lint rules.

Refs

New pseudo-elements

Name	Spec	MDN
::checkmark	open-ui/selectlist	MDN
::column	css-multicol-2	MDN
::picker()	open-ui/selectlist	MDN
::picker-icon	open-ui/selectlist	MDN
::scroll-button()	css-overflow-5	MDN
::scroll-marker	css-overflow-5	MDN
::scroll-marker-group	css-overflow-5	MDN

New pseudo-classes

Name	Spec	MDN
:active-view-transition-type()	css-view-transitions-2	MDN
:has-slotted	css-scoping-2	MDN
:target-current	css-overflow-5	MDN
:target-before	css-overflow-5	MDN
:target-after	css-overflow-5	MDN

New properties

Name	Spec	MDN
dynamic-range-limit	css-color-hdr	MDN
overlay	css-position-4	MDN
reading-flow	css-display-4	MDN
reading-order	css-display-4	MDN
scroll-marker-group	css-overflow-5	MDN
scroll-target-group	css-overflow-5	MDN

[changeset-bot]

🦋 Changeset detected

Latest commit: 264a0e5

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]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 2667584f-ec8e-479d-b8ca-51cc4019af91

📥 Commits

Reviewing files that changed from the base of the PR and between fe9ff6b and 6a1fed4.

⛔ Files ignored due to path filters (3)

• crates/biome_css_analyze/tests/specs/correctness/noUnknownProperty/valid.css.snap is excluded by !**/*.snap and included by **
• crates/biome_css_analyze/tests/specs/correctness/noUnknownPseudoClass/valid.css.snap is excluded by !**/*.snap and included by **
• crates/biome_css_analyze/tests/specs/correctness/noUnknownPseudoElement/valid.css.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (5)

• .changeset/modern-css-keywords.md
• crates/biome_css_analyze/src/keywords.rs
• crates/biome_css_analyze/tests/specs/correctness/noUnknownProperty/valid.css
• crates/biome_css_analyze/tests/specs/correctness/noUnknownPseudoClass/valid.css
• crates/biome_css_analyze/tests/specs/correctness/noUnknownPseudoElement/valid.css

---

Walkthrough

This PR extends CSS language support by introducing modern CSS keywords across properties, pseudo-elements, and pseudo-classes. It adds six new known properties (dynamic-range-limit, overlay, reading-flow, reading-order, scroll-marker-group, scroll-target-group), seven new pseudo-elements (including ::checkmark, ::picker, ::scroll-marker variants), and five new pseudo-classes (:has-slotted, :target-before, :target-after, :target-current, :active-view-transition-type). The keywords registry is updated alongside corresponding test files to validate these constructs.

Possibly related PRs

• fix(linter): add support for active-view-transition pseudo-class #8787 – Expands OTHER\_PSEUDO\_CLASSES with View Transitions-related pseudo-classes in the same keywords file.
• fix(css): allow navigation property for view-transition (fixes #7340)  #7353 – Extends KNOWN\_PROPERTIES in keywords.rs with additional CSS properties (navigation).
• fix(lint): regression of the noUnknownPseudoElement rule #9100 – Refines pseudo-element and pseudo-class recognition logic in the noUnknownPseudoElement rule.

Suggested reviewers

• ematipico
• siketyan

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarises the main change: adding support for modern CSS properties, pseudo-classes, and pseudo-elements to the codebase.
Description check	✅ Passed	The description is directly related to the changeset, providing clear details about which CSS keywords were added and why, along with comprehensive references to specifications and MDN documentation.

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[ematipico]

Lovely, thank you!

[ematipico]

It seems that not all tests were run. @willfarrell can you please look after it? CI is failing

[codspeed-hq]

Merging this PR will not alter performance

✅ 29 untouched benchmarks
⏩ 187 skipped benchmarks¹

---

_{Comparing willfarrell:feature/modern-css (264a0e5) with main (c311974)²}

Footnotes

1. 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. ↩

2. No successful run was found on main (9315453) during the generation of this report, so c311974 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[willfarrell]

Pushed an update, will watch for pass

[willfarrell]

We're all good :)