Refactor CSS node types with reusable type builders

[bartveneman]

Summary

This refactor introduces reusable type builders (Toggle, WithClone, and Leaf) to reduce duplication across ~40 CSS node type definitions. These are pure type-level utilities that compile away entirely, improving maintainability without runtime cost.

Key Changes

• Added Toggle<HasKey, ValueKey, T> type: A discriminated union pattern for optional fields gated by boolean flags (e.g., has_prelude / prelude). Replaces repeated inline union patterns throughout the file.

• Added WithClone<T> type: Wraps a node type to add a clone() method with proper return type inference (ToPlain<T>). Eliminates repetitive clone method declarations.

• Added Leaf<Type, Name, Extra> type: Combines CSSNode, type tag, and optional extra fields for leaf nodes (nodes without children). Significantly reduces boilerplate for simple node types.

• Refactored all node type definitions to use these builders:

  • Structural nodes: StyleSheet, Rule, Atrule, Declaration, Selector, SelectorList, Block, Comment, Raw
  • Value nodes: Identifier, Number, Dimension, String, Hash, Function, Operator, Parenthesis, Url, UnicodeRange, Value
  • Selector nodes: TypeSelector, ClassSelector, IdSelector, AttributeSelector, PseudoClassSelector, PseudoElementSelector, Combinator, UniversalSelector, NestingSelector, NthSelector, NthOfSelector, LangSelector
  • At-rule prelude nodes: AtrulePrelude, MediaQuery, MediaFeature, MediaType, ContainerQuery, SupportsQuery, SupportsDeclaration, LayerName, PreludeSelectorList, PreludeOperator, FeatureRange

Implementation Details

• The Toggle type replaces verbose union patterns like ({ readonly has_X: true } & { readonly X: T }) | ({ readonly has_X: false } & { readonly X: null }) with a single, reusable construct.
• BlockChild now uses Toggle for its has_next / next_sibling pattern.
• All type definitions maintain identical semantics and exported interfaces—this is purely a refactoring for code clarity and maintainability.
• The builders are documented with JSDoc comments explaining their purpose and usage.

https://claude.ai/code/session_01FuvCERnifYS6ggHAXMwVkD

[github-actions]

⚠️ Duplicate Dependencies (found: 11, threshold: 1)

📦 Package	📋 Versions
tinybench	2 versions root@ @vitest/coverage-v8@4.1.10 vitest@4.1.10 tinybench@2.9.0 root@ tinybench@6.0.2
js-tokens	2 versions root@ @vitest/coverage-v8@4.1.10 ast-v8-to-istanbul@1.0.5 js-tokens@10.0.0 root@ tailwindcss@2.2.19 cosmiconfig@7.1.0 parse-json@5.2.0 @babel/code-frame@7.27.1 js-tokens@4.0.0
@emnapi/core	2 versions root@ knip@6.27.0 oxc-resolver@11.21.3 @oxc-resolver/binding-wasm32-wasi@11.21.3 @emnapi/core@1.11.0 root@ @vitest/coverage-v8@4.1.10 ... rolldown@1.1.5 @rolldown/binding-wasm32-wasi@1.1.5 @emnapi/core@1.11.1
@emnapi/runtime	2 versions root@ knip@6.27.0 oxc-resolver@11.21.3 @oxc-resolver/binding-wasm32-wasi@11.21.3 @emnapi/runtime@1.11.0 root@ @vitest/coverage-v8@4.1.10 ... rolldown@1.1.5 @rolldown/binding-wasm32-wasi@1.1.5 @emnapi/runtime@1.11.1
picomatch	2 versions root@ tailwindcss@2.2.19 chokidar@3.6.0 anymatch@3.1.3 picomatch@2.3.2 root@ @vitest/coverage-v8@4.1.10 vitest@4.1.10 @vitest/mocker@4.1.10 vite@8.1.4 picomatch@4.0.5
postcss-value-parser	2 versions root@ tailwindcss@2.2.19 reduce-css-calc@2.1.8 postcss-value-parser@3.3.1 root@ tailwindcss@2.2.19 autoprefixer@10.4.23 postcss-value-parser@4.2.0
glob-parent	2 versions root@ tailwindcss@2.2.19 chokidar@3.6.0 glob-parent@5.1.2 root@ tailwindcss@2.2.19 glob-parent@6.0.2
yaml	2 versions root@ tailwindcss@2.2.19 cosmiconfig@7.1.0 yaml@1.10.3 root@ @vitest/coverage-v8@4.1.10 vitest@4.1.10 @vitest/mocker@4.1.10 vite@8.1.4 yaml@2.9.0
is-arrayish	2 versions root@ tailwindcss@2.2.19 cosmiconfig@7.1.0 parse-json@5.2.0 error-ex@1.3.4 is-arrayish@0.2.1 root@ tailwindcss@2.2.19 color@4.2.3 color-string@1.9.1 simple-swizzle@0.2.4 is-arrayish@0.3.4
get-tsconfig	2 versions root@ knip@6.27.0 get-tsconfig@4.14.0 root@ tsdown@0.22.8 rolldown-plugin-dts@0.27.9 get-tsconfig@5.0.0-beta.5
@oxc-project/types	2 versions root@ knip@6.27.0 oxc-parser@0.137.0 @oxc-project/types@0.137.0 root@ @vitest/coverage-v8@4.1.10 ... vite@8.1.4 rolldown@1.1.5 @oxc-project/types@0.139.0

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🎉 Package Size Decrease

📦 Package	📏 Base Size	📏 Source Size	📈 Size Change
@projectwallace/css-parser	41.3 kB	41.2 kB	-100 B