Steps to reproduce

• Run npm install
• Run npm run build
• Inspect the runtime file in dist/runtime~main.303.43e9c511529c185ee664.js

Example output

/******/ 		__webpack_require__.miniCssF = (chunkId) => {
/******/ 			// return url for filenames based on template
/******/ 			return "" + ({"179":"main","303":"runtime~main"}[chunkId] || chunkId) + "." + chunkId + "." + {"179":"c539139b868f46f81e90","229":"31d6cfe0d16ae931b73c","851":"31d6cfe0d16ae931b73c"}[chunkId] + ".css";
/******/ 		};

Bug 1 - Extra chunkId

__webpack_require__.miniCssF contains a mapping "303":"runtime~main", however chunk#303 does not have a CSS file.

Bug 2 - Extra content hashes

__webpack_require__.miniCssF contains mappings for "229":"31d6cfe0d16ae931b73c" and "851":"31d6cfe0d16ae931b73c", however those chunks don't have CSS files.

Correct output

The output should be:

/******/ 		__webpack_require__.miniCssF = (chunkId) => {
/******/ 			// return url for filenames based on template
/******/ 			return "" + ({"179":"main"}[chunkId] || chunkId) + "." + chunkId + "." + {"179":"c539139b868f46f81e90"}[chunkId] + ".css";
/******/ 		};

As chunk#179 (i.e. main) is the only chunk with a CSS file, main.179.c539139b868f46f81e90.css

Variations

This don't fix the problem:

  plugins: [new MiniCssExtractPlugin({
    filename: '[name].[id].[chunkhash].css',
    chunkFilename: '[name].[id].[chunkhash].css',
  })],

This fixes bug#2, but not bug#1

  plugins: [new MiniCssExtractPlugin()],