Cssnano: Sourcemap gets minified with Webpack + postcss + miniextractcssplugin

[aryaroudi]

Hi Guys,

I have a problem, When I use cssnano with postcss-loader in Webpack 4 and mini extract CSS plugin the Sourcemap gets minified too. Example:

#### webpack.config.js

module.exports = {
  devtool: 'source-map',
  entry: {
    foo: [
      './base.css',
      './basic.css'
    ]
  },
  optimization: {
    splitChunks: {
      cacheGroups: {
        fooStyles: {
          name: 'foo',
          test: (m,c,entry = 'foo') => m.constructor.name === 'CssModule' && recursiveIssuer(m) === entry,
          chunks: 'all',
          enforce: true
        }
      }
    }
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
    })
  ],
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          MiniCssExtractPlugin.loader,
          {
            loader: 'css-loader',
            options: {
              url: false,
      }
    },
    {
      loader: 'postcss-loader',
      options: {
        sourceMap: true,
        ident: 'postcss',
        plugins: [
          require('autoprefixer')({
                        browsers: [
                          '>1%',
                          'last 4 versions',
                          'Firefox ESR',
                          'not ie < 9', // React doesn't support IE8 anyway
                        ],
                        flexbox: 'no-2009',
                      }),
                      require('cssnano')({ preset: 'default' })
        ]
      }
    }
        ],
      }
    ]
  }
}

What it is wrong here?

[aryaroudi]

Ok. It turns out that the sourcemap option should be set inside the css-loader also:

        {
            loader: 'css-loader',
            options: {
              url: false,
              sourceMap: true
      }

[alexander-akait]

@aryaroudi don't use cssnano in postcss-loader, use https://github.com/intervolga/optimize-cssnano-plugin, using on postcss-loader makes impossible same optimization, also css-loader can rewrite some css stuff

[aryaroudi]

@aryaroudi don't use cssnano in postcss-loader, use https://github.com/intervolga/optimize-cssnano-plugin, using on postcss-loader makes impossible same optimization, also css-loader can rewrite some css stuff

Very Good point. It would be great if you guys update the postcss-loader documentation, many people choose the bad approach.

Thanks