index.js

import styles from './styles.scss';

styles.scss

@import "~bulma/sass/utilities/all";
@import "src/config";
@import "~bulma/sass/grid/columns";

.summaryContainer {
  @extend .columns;
  padding: 2rem 0;
  margin: 0;
}

webpack.dev.js

const extractTextPluginOptions = shouldUseRelativeAssetPaths
  ? // Making sure that the publicPath goes back to to build folder.
    { publicPath: Array(cssFilename.split('/').length).join('../') }
  : {};

{
  test: /\.css$/,
  loader: ExtractTextPlugin.extract(
    Object.assign(
      {
        fallback: require.resolve('style-loader'),
        use: [
          {
            loader: require.resolve('css-loader'),
            options: {
              importLoaders: 1,
              modules: true,
              minimize: true,
              sourceMap: true,
            },
          },
          {
            loader: require.resolve('postcss-loader'),
            options: {
              // Necessary for external CSS imports to work
              // https://github.com/facebookincubator/create-react-app/issues/2677
              ident: 'postcss',
              plugins: () => [
                cssnano({
                  discardDuplicates: true,
                  discardUnused: true,
                  discardEmpty: true,
                }),
                require('postcss-flexbugs-fixes'),
                autoprefixer({
                  browsers: [
                    '>1%',
                    'last 4 versions',
                    'Firefox ESR',
                    'not ie < 9', // React doesn't support IE8 anyway
                  ],
                  flexbox: 'no-2009',
                }),
              ],
            },
          },
        ],
      },
      extractTextPluginOptions
    )
  ),
  // Note: this won't work without `new ExtractTextPlugin()` in `plugins`.
},
{
  test: /\.(scss|sass)$/,
  loader: ExtractTextPlugin.extract(
    Object.assign(
      {
        fallback: require.resolve('style-loader'),
        use: [
          {
            loader: require.resolve('css-loader'),
            options: {
              importLoaders: 1,
              modules: true,
              minimize: true,
              sourceMap: true,
              localIdentName: '[name]__[local]___[hash:base64:5]',
            },
          },
          {
            loader: require.resolve('sass-loader'), // compiles Sass to CSS
          },
        ],
      },
      extractTextPluginOptions
    )
  ),
},