Failed to extacrt source with @import external resources and source mapping

[OpportunityLiu]

• Operating System: Windows 10 1904
• Node Version: v12.18.1
• NPM Version: 6.14.5
• webpack Version: 5.1.3
• css-loader Version: 5.0.0

Expected Behavior

Build with no error.

Actual Behavior

ERROR in ./src/components/elements/icon.scss?module
Module build failed (from ./node_modules/extract-loader/lib/extractLoader.js):
TypeError: Cannot read property 'sources' of undefined
    at cssWithMappingToString (node_modules\css-loader\dist\runtime\cssWithMappingToString.js:26:33)
    at node_modules\css-loader\dist\runtime\api.js:14:21
    at Array.map (<anonymous>)
    at Array.toString (node_modules\css-loader\dist\runtime\api.js:13:17)
    at extractExports (node_modules\extract-loader\lib\extractLoader.js:182:269)
    at node_modules\extract-loader\lib\extractLoader.js:171:45
    at Generator.next (<anonymous>)
    at step (node_modules\babel-runtime\helpers\asyncToGenerator.js:17:30)
    at babel-runtime\helpers\asyncToGenerator.js:28:13

Code

// webpack.config.js
// If your code blocks are over 20 lines, please paste a link to a gist
// (https://gist.github.com).
module.exports = (env = {}, argv = {}) => {
  const config = {
    target: "web",
    entry: "./index.js",
    module: {
      rules: [
        {
          test: /\.css$/i,
          use: [
            "file-loader",
            "extract-loader",
            {
              loader: "css-loader",
              options: {
                importLoaders: 1,
              },
            },
            {
              loader: "postcss-loader",
              options: {
                postcssOptions: { plugins: ["postcss-preset-env"] },
              },
            },
          ],
        },
      ],
    },
    devtool: 'inline-source-map'
  };

  return config;
};

@import url('https://cdn.bootcss.com/material-design-icons/3.0.2/iconfont/material-icons.css');

span {
  font-family: 'Material Icons';
}

How Do We Reproduce?

git clone https://github.com/OpportunityLiu/css-extract-with-url
yarn
yarn build

[alexander-akait]

Report the problem to extract-loader, my recommendation is migrate on mini-css-extract-plugin (official plugin)

[OpportunityLiu]

Thank you for your response. I'm using it with lit-scss-loader, can't migrate to mini-css-extract-plugin.

[alexander-akait]

Sorry nothing to fix here