`@vitest/coverage-istanbul` breaks when running tests in `@vitest/browser` with `scss`

[alecgibson]

Describe the bug

Trying to run coverage with:

• @vitest/browser@3.2.3
• @vitest/coverage-istanbul@3.2.3
• sass-embedded@1.89.2

Will accidentally try to instrument the SASS in an SFC.

This worked fine in @vitest/coverage-istanbul@3.1.4

I suspect this bug was introduced by #7939 and we're running into issues because the transformed id looks like App.vue?vue&type=style&index=0&lang.scss, but the check is ignoring files that end in .css (which doesn't match .scss).

Reproduction

1. Clone https://github.com/alecgibson/vitest-coverage-bug
2. npm i
3. npm test
4. See errors in console about coverage trying to parse SCSS, when I would expect no errors

System Info

System:
    OS: macOS 15.5
    CPU: (10) arm64 Apple M1 Pro
    Memory: 124.19 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.9.0 - ~/.nvm/versions/node/v20.9.0/bin/node
    Yarn: 1.22.22 - ~/.yarn/bin/yarn
    npm: 10.1.0 - ~/.nvm/versions/node/v20.9.0/bin/npm
    pnpm: 10.5.2 - ~/.nvm/versions/node/v20.9.0/bin/pnpm
    bun: 1.0.15 - ~/.bun/bin/bun
  Browsers:
    Chrome: 137.0.7151.70
    Safari: 18.5
  npmPackages:
    @vitejs/plugin-vue: ^5.2.4 => 5.2.4 
    @vitest/browser: ^3.2.3 => 3.2.3 
    @vitest/coverage-istanbul: ^3.2.3 => 3.2.3 
    playwright: ^1.53.0 => 1.53.0 
    vite: ^6.3.5 => 6.3.5

Used Package Manager

npm

Validations

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• 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.
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• The provided reproduction is a minimal reproducible example of the bug.

[AriPerkkio]

These are quite difficult to detect. The file is .vue but it's not Vue. 🤷

We need to add the extension here:

vitest/packages/coverage-istanbul/src/provider.ts

Lines 63 to 69 in 3414692

	onFileTransform(sourceCode: string, id: string, pluginCtx: any): { code: string; map: any } | undefined {
	// Istanbul/babel cannot instrument CSS - e.g. Vue imports end up here.
	// File extension itself is .vue, but it contains CSS.
	// e.g. "Example.vue?vue&type=style&index=0&scoped=f7f04e08&lang.css"
	if (id.endsWith('.css')) {
	return
	}