compiler.js

const path = require('path')
const webpack = require('webpack')
const Memoryfs = require('memory-fs')

module.exports = (fixture, options = {}) => {
  const compiler = webpack({
    stats: {
      // Examine all modules
      maxModules: Infinity,
      // Display bailout reasons
      optimizationBailout: true
    },
    mode: options.mode || 'development',
    context: __dirname,
    entry: `./${fixture}`,
    output: {
      path: path.resolve(__dirname),
      filename: 'bundle.js'
    },
    resolve: {
      extensions: ['.ts', '.tsx', '.js']
    },
    module: {
      rules: [
        ...(options.prerules || []),
        {
          test: /\.tsx?$/,
          use: {
            loader: path.resolve(__dirname, '../lib/index.js'),
            options: {
              tsconfig: path.resolve(__dirname, options.tsconfig != null ? options.tsconfig : 'tsconfig.json'),
              externDir: options.externDir
            }
          }
        }, ...(options.rules || [])
      ]
    },
    plugins: [
      new webpack.optimize.ModuleConcatenationPlugin()
    ],
    optimization: {
      minimize: true,
      // minimizer: options.minimizer,
      usedExports: true,
      splitChunks: {
        minSize: 0
      },
      concatenateModules: true
    }
  })

  const mfs = new Memoryfs()

  compiler.outputFileSystem = mfs

  const getCode = (stats) =>
    stats.toJson().modules[0].source

  return new Promise((resolve, reject) => {
    compiler.run((err, stats) => {
      if (err || stats.hasErrors()) {
        reject(err != null ? err : stats.compilation.errors)
        return
      }

      const result = mfs.readFileSync(path.resolve(__dirname, 'bundle.js')).toString()

      resolve([result, stats, getCode(stats)])
    })
  })
}