empty css rollup input generates empty js output

[MoritzLoewenstein]

What I am doing

Empty CSS (or SCSS) file as input in vite rollupOptions config.

export default {
  build: {
    manifest: true,
    rollupOptions: {
      input: [/* 'test.scss', */ 'test.css'],
    },
  },
};

What i expect to happen

I expected either no output for this file (and no manifest entry),
or an empty css file output and a manifest entry like this:

{
  "test.css": {
    "file": "assets/test-l0sNRNKZ.css",
    "name": "test",
    "src": "test.css",
    "isEntry": true
  }
}

What is actually happening

Vite generates an empty js file as output when running vite build, e.g. this manifest entry:

{
  "test.css": {
    "file": "assets/test-l0sNRNKZ.js",
    "name": "test",
    "src": "test.css",
    "isEntry": true
  }
}

Note: the stackblitz reproduction does error when compiling scss, but the same thing happens when building an empty scss file.

Reproduction

https://stackblitz.com/edit/vite-empty-css-fzjoe4md?file=vite.config.js

Steps to reproduce

Run npm install followed by npm run build

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    vite: ^6.3.3 => 6.3.3

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
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• The provided reproduction is a minimal reproducible example of the bug.

[nakul-py]

Hey @MoritzLoewenstein, Vite skips empty CSS files during build. You can add a dummy class (like :root {}) to make sure it's processed and output as a .css file.

Results

Before adding dummy class.

After adding dummy class.

[MoritzLoewenstein]

Hey @nakul-py ,
this is true, but when using lightningcss as the css transformer the same thing happens for every css file that minifies to an empty file (which may not always be obvious): vite-empty-css-fzjoe4md-k3rcgpsn
Note: lightningcss does not seem to work on stackblitz, only the vite config changed from the previous reproduction.

[nakul-py]

Hey @MoritzLoewenstein If test.css is empty or only has comments, LightningCSS might be stripping it all out. I hope this works vite-empty-css

[MoritzLoewenstein]

This will "work" in the sense that it will generate a css output file, my issue is that I am building a custom vite php integration which will read the manifest. It just seems illogical that a css/scss entry can generate a js output in any case. If that is expected I will handle it in my integration, I was just thinking that it seems unintuitive / appears to be a bug.