Description

This PR ports the fix from vitejs/vite#20585 to rolldown's builtin vite-css plugin. The issue was that CSS entry point names were being incorrectly transformed in the manifest output (e.g., foo.scss → foo.css), making it impossible to locate CSS entries by their original names.

Problem

When CSS files are used as entry points with custom names (e.g., styles/tailwind.scss or bar.custom), the manifest was:

1. Transforming the entry names to .css extension regardless of the original name
2. Only storing whether an asset was an entry (boolean), not preserving the actual entry name

This broke use cases where:

• Entry names had non-CSS extensions (.scss, .less, etc.)
• Custom entry names without extensions were used (e.g., bar.custom)
• The entry name needed to match the original input configuration

Solution

Changed the CSS entries tracking mechanism from a Set to a Map to preserve the original chunk names:

Key Changes

1. CSS Entries Storage: Changed from Set<referenceId> to Map<chunkName, referenceId>

   // Before
   pub struct CSSEntriesCache {
     pub inner: FxDashSet<ArcStr>,
   }
   
   // After
   pub struct CSSEntriesCache {
     pub inner: FxDashMap<String, ArcStr>,
   }

2. Entry Tracking: Store chunk name along with reference ID

   // Before
   css_entries_cache.inner.insert(reference_id);
   
   // After
   css_entries_cache.inner.insert(chunk.name.to_string(), reference_id);

3. Manifest Output: Added name field with the unmangled entry name

   pub struct ManifestChunk {
     // ... other fields
     pub name: Option<String>,         // NEW: preserves original entry name
     pub names: Option<Vec<String>>,   // Kept for backward compatibility
   }

Example

With an entry point named styles/tailwind.scss, the manifest will now include:

{
  "styles/tailwind.scss": {
    "file": "assets/tailwind-abc123.css",
    "src": "styles/tailwind.scss",
    "isEntry": true,
    "name": "styles/tailwind.scss",
    "names": ["styles/tailwind.css"]
  }
}

The name field preserves the original styles/tailwind.scss entry name, while names is kept for backward compatibility.

Backward Compatibility

• The names field is preserved in the manifest output for backward compatibility
• The new name field is added as an optional field
• Existing consumers will continue to work without changes

Testing

• ✅ All Rust clippy checks pass
• ✅ All Rust formatting checks pass
• ✅ TypeScript linting and type checking pass
• ✅ Build completes successfully

Related

• Vite PR: fix(build): replace names in the manifest with unmangled name for CSS assets vitejs/vite#20585
• Original Vite discussion: feat(build): provide names for asset entrypoints vitejs/vite#19912 (comment)

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.