Duplicated css module file when using @value ... from ... inside <style module> block

[fnlctrl]

Version

14.2.1
Webpack 4.1.1

Reproduction link

https://github.com/fnlctrl/vue-loader-duplicate-cssm-import-repro

Steps to reproduce

1. npm install

2. npm run build
   Check dist/bundle.js, using js imported style works fine, colors.css is not duplicated`

3. Uncomment the @value Red-500 from './colors.css'; line in app.vue, and npm run build
   Check dist/bundle.js, you'll now see colors.css duplicated.
   This bug causes colors.css to be duplicated every time a component
   uses @value ... from ... inside <style module> block

What is expected?

Only one colors.css

What is actually happening?

Duplicated colors.css

[yyx990803]

The root cause of this is that css-loader appends the importing module's inline loader request prefixes to all imported modules. So for import 'css-loader?foo!colors.css' and import 'css-loader?bar!colors.css', any files imported by colors.css will be duplicated because technically they might need to be processed with different options.

This is unfortunately unfixable in v14. But I managed to get it resolved in v15.