[Bug]: css.experiments prefers-color-scheme at import not being applied

[daveskybet]

System Info

System:
OS: macOS 14.6.1
CPU: (10) arm64 Apple M1 Pro
Memory: 87.59 MB / 16.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 20.9.0 - ~/.asdf/installs/nodejs/20.9.0/bin/node
npm: 10.1.0 - ~/.asdf/installs/nodejs/20.9.0/bin/npm
pnpm: 9.15.2 - ~/.asdf/installs/nodejs/20.9.0/bin/pnpm
Watchman: 2024.01.22.00 - /opt/homebrew/bin/watchman
Browsers:
Chrome: 132.0.6834.160
Safari: 17.6
npmPackages:
@rspack/cli: ^1.2.2 => 1.2.2
@rspack/core: ^1.2.2 => 1.2.2

Details

On using the native css.experiments in Rspack, attempting to use the (prefers-color-scheme) syntax on css @import, the css file gets included at compilation without being wrapped in an @media query, causing the expected conditional not to be applied.

I'm not sure whether this is a bug or an expected unimplemented feature as per https://github.com/web-infra-dev/rspack/blob/cc5e3f6a49073b354c08ec4b8c75142e602d02ee/crates/rspack_plugin_css/webpack_css_cases_to_be_migrated/at-import-layer/style.css

Can you advise? Out of a large application i have one instance of this syntax causing me to revert to css-loader over handling everything in Rspack, bumping up the build time significantly.

Reproduce link

https://github.com/daveskybet/repro-import-prefers-color-scheme

Reproduce Steps

1. @import a css file using the (prefers-color-scheme) syntax
2. On compilation see that the css file has been included without being wrapped in a @media query