feat(v4): support CSS directives

[colinaaa]

Summary

Support using directives like @apply, @custom-variant, @variant and @utility in regular .css files.

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Summary of Changes

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This pull request introduces support for various Tailwind CSS v4 directives like @apply, @custom-variant, @variant, and @Utility within regular CSS files. This is achieved by integrating the official @tailwindcss/postcss plugin into the Rsbuild PostCSS pipeline, enhancing the plugin's capabilities for modern Tailwind CSS usage.

Highlights

• CSS Directives Support: Enabled the use of Tailwind CSS v4 directives such as @apply, @custom-variant, @variant, and @Utility directly in .css files.
• PostCSS Plugin Integration: Integrated the @tailwindcss/postcss plugin into the Rsbuild PostCSS pipeline to automatically process these new CSS directives.
• Improved Theme Resolution: Enhanced the theme path resolution logic to correctly handle relative paths for Tailwind CSS themes.
• Comprehensive Test Coverage: Added new test cases and example files to validate the functionality of the newly supported CSS directives.

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Changelog

• README.md
  • Added a new section detailing the automatic support for CSS directives like @apply and @plugin.
  • Included a CSS code example demonstrating @apply usage.
• package.json
  • Moved @tailwindcss/postcss from devDependencies to dependencies.
  • Added postcss as a devDependency.
• pnpm-lock.yaml
  • Updated the lockfile to reflect the changes in package.json, specifically moving @tailwindcss/postcss and adding postcss.
• src/index.ts
  • Imported tailwindPostCSSPlugins from the new postcss.ts file.
  • Modified the theme option resolution to ensure it's an absolute path.
  • Integrated the tailwindPostCSSPlugins into the Rsbuild PostCSS configuration, ensuring they run before other PostCSS plugins.
• src/postcss.ts
  • Added a new file defining injectTailwindThemePlugin and tailwindPostCSSPlugins.
  • Defined injectTailwindThemePlugin as a PostCSS plugin that prepends an @import rule for the Tailwind theme.
  • Exported tailwindPostCSSPlugins as an array containing injectTailwindThemePlugin and the main @tailwindcss/postcss plugin.
• test/css-directives/index.test.ts
  • Added a new test file to verify the correct application of @apply, @Utility, @custom-variant, and @variant directives using Playwright.
• test/css-directives/src/app.css
  • Added a new CSS file containing examples of @custom-variant, @Utility, @apply, and @variant usage for testing.
• test/css-directives/src/index.js
  • Added a new JavaScript file to create HTML elements and apply classes for testing the CSS directives.
• test/functions/config/functions-theme.css
  • Removed the layer(theme) from the @import statement for tailwindcss/theme.
  • Removed the @layer components block, which was moved to a separate file.
• test/functions/src/components.css
  • Added a new CSS file containing the @layer components block previously found in functions-theme.css.
• test/functions/src/index.js
  • Added an import statement for the new components.css file.

Activity

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Code Review

This pull request adds support for using Tailwind CSS directives like @apply in regular CSS files by integrating @tailwindcss/postcss. However, a CSS injection vulnerability was identified in src/postcss.ts where the theme option is not properly escaped when injected into an @import rule, potentially allowing arbitrary CSS injection. Additionally, I've found a potential runtime error in the new PostCSS plugin and a minor inconsistency in the README documentation.