stylus-loader.js

const { resolve } = require('path')
const autoprefixer = require('autoprefixer')
const stylusMixins = require('stylus-mixins')
const poststylus = require('poststylus')

module.exports = () => ([
  {
    loader: require.resolve('css-loader'),
    options: {
      minimize: true,
      modules: true,
      localIdentName: '[name]__[local]--[hash:base64:5]'
    }
  },
  {
    loader: require.resolve('stylus-loader'),
    options: {
      use: [
        stylusMixins(),
        poststylus([ autoprefixer ])
      ]
    }
  }
])

webpack.config.js

const path = require('path')
const createStylusLoader = require('../config/stylus-loader')

module.exports = {
  module: {
    rules: [
      {
        test: /\.styl$/,
        use: [ require.resolve('style-loader'), ...createStylusLoader() ]
      }
    ]
  },
  node: {
    fs: 'empty'
  }
}