client.js

var styles = require('./error.styl');

error.styl

body
  width 10px;

package.json

{
  "name": "error",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "extract-text-webpack-plugin": "^0.8.2"
  }
}

webpack.config.js

var path    = require('path');
var extract = require('extract-text-webpack-plugin');

module.exports = {
  entry: {
    main: [
      './client.js'
    ]
  }
, output: {
    path: path.resolve(__dirname, '../assets')
  , filename: '[name].js'
  , chunkFilename: '[name]-[chunkhash].js'
  }

, progress: true
, devtool: 'sourcemap'

, module: {
    loaders: [
      {
        test: /\.styl$/
      , loader: 'style!extract-text-webpack-plugin/loader!css!stylus'
      , exclude: /node_modules/
      }
    ]
  , preLoaders: [
      {
        test: /\.styl$/
      , loader: 'stylint?{"reporter":"stylint-stylish","semicolons":{"expect":"never","error":true}}'
      , exclude: /node_modules/
      }
    ]
  }
  , plugins: [
    new extract('main.css', {
      allChunks: true
    })
  ]
};