[Bug]: Rspack ignores layers specified on imports in the main css file

[dnwhte]

Version

System:
    OS: Windows 10 10.0.19045
    CPU: (8) x64 Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz
    Memory: 5.32 GB / 15.92 GB
  Browsers:
    Chrome: 127.0.6533.89
    Edge: Chromium (127.0.2651.74)
  npmPackages:
    @rsbuild/core: ^1.0.1-beta.9 => 1.0.1-beta.9
    @rsbuild/plugin-react: ^1.0.1-beta.9 => 1.0.1-beta.9

Details

The builtin:lightningcss-loader ignores layers specified on imports in the root css file.

Index.css

@layer reset, base, components;

@import './a.css' layer(reset);
@import './b.css' layer(base);

Expected Output

@layer reset {
  .a {
    color: red;
  }
}

@layer base {
  .b {
    color: green;
  }
}

@layer components;

Actual Output

.a {
  color: red;
}

.b {
  color: green;
}

@layer reset, base, components;

Reproduce link

https://codesandbox.io/p/devbox/9lyypl?migrateFrom=7rj2zn

Reproduce Steps

1. Use the builtin:lightningcss-loader in your config
2. In the root css file import another css file and set a layer for it. - @import './component.css' layer(components)
3. Run the rsbuild
4. Check of the components are properly layered in the output css

[chenjiahan]

I think this is an unsupported CSS feature of Rspack and has nothing to do with lightningcss-loader.

• webpack + css-loader + mini-css-extract-plugin: the generated CSS bundle is as expected.
• Rspack + css-loader + CssExtractRspackPlugin: the generated CSS bundle is missing layers.

[chenjiahan]

Maybe related: #5340

[stale]

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[chenjiahan]

Fixed by #7583