sources field of map does not contain path.

[WearyMonkey]

• Operating System:
  OSX 10.14.6 (18G95)

• Node Version:
  v10.16.0

• NPM Version:
  yarn 1.21.1

• webpack Version:
  4.41.5

• css-loader Version:
  3.4.1

Expected Behavior

Sources field of the sourcemap contains the path relative to the context. e.g. "sources":["src/foo/index.css"]

Actual Behavior

Sources field of the sourcemap contains just the file name. e.g. "sources":["index.css"]

Code

// webpack.config.js
const MiniCssExtractPlugin = require('mini-css-extract-plugin');
const path = require('path');

module.exports = {
  entry: './src/foo/index.css',
  devtool: 'source-map',
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader?sourceMap',
        ]
      }
    ]
  },
  plugins: [new MiniCssExtractPlugin()],
};

How Do We Reproduce?

1. Create a webpack project with the above configuration.
2. yarn webpack
3. cat dist/main.css.map

Note, the sources field is "sources":["webpack:///index.css"]

[alexander-akait]

Bug on css-loader side webpack-contrib/css-loader#622 because postcss generate relative source maps, not absolute, so we can't contexity them in the right now, anyway it is fixed in postcss@8 (I help release will be near future - next week) and we will fix it, close in favor webpack-contrib/css-loader#622

[alexander-akait]

Just note - postcss-loader has the same bug