webpack.config.js

const path = require('path')
const fs = require('fs-extra')
const glob = require('glob')
const chokidar = require('chokidar')
const WatchExternalFilesPlugin = require('webpack-watch-files-plugin').default

const rootFolder = path.resolve(__dirname, '..')
const outputFolder = path.resolve(rootFolder, 'test-karma-webpack')
const testFolder = path.resolve(rootFolder, 'test')
const lockFile = path.resolve(rootFolder, 'package-lock.json')

// all our test files
const testGlob = testFolder + '/**/*.test.js'

// find all the browser test files and assign them to their own name, don't bundle them
const testFiles = glob.sync(testGlob).sort()
const testEntries = testFiles.reduce((acc, file) => {
  acc[file.replace(rootFolder, '')] = file
  return acc
}, {})

// debug build paths if needed
// console.log({rootFolder, testFiles, testEntries, outputFolder, testFolder, lockFile})
console.log('karma test files:')
console.log(Object.keys(testEntries))

module.exports = {
  // each test file is its own entry
  entry: testEntries,

  output: {
    // output each test entry to its own file name
    filename: '[name]',
    path: outputFolder,

    // clean the dist folder on each rebuild
    clean: true,
  },

  plugins: [
    // watch the entire test folder, not just our entries
    new WatchExternalFilesPlugin({
      files: [testGlob],
    }),
  ],

  module: {
    rules: [
      // plebbit-js doesn't need babel, but we should write our tests
      // with it to make sure it doesn't break for users who use it
      // like react users for example
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
          options: {
            // the most common option used by people
            presets: ['@babel/preset-env'],

            // fix ReferenceError: regeneratorRuntime is not defined
            plugins: ['@babel/plugin-transform-runtime'],
          },
        },
      },
    ],
  },

  /* 

    DO NOT USE FALLBACKS, ALIASES OR DEFINE/POLYFILL GLOBALS
    it will break using plebbit-js in projects that import it
    instead split the files that use node only code in:
      src/runtime/node
      src/runtime/browser
    resolve: {
        DO NOT USE
        fallback: {
            buffer: false,
            crypto: false,
            dns: false,
            fs: false,
            http: false,
            https: false,
            net: false,
            path: false,
            stream: false,
            util: false
        }

        DO NOT USE
        alias: {
            process: false
        }
    }
    */
}

// reset the webpack folder
fs.removeSync(outputFolder)

// if a new test file is found, restart webpack watcher
// this is needed because the webpack entries cannot be
// modified dynamically while watching, a new file is a new entry
chokidar.watch(testFolder, {persistent: false}).on('all', async (event, path) => {
  glob(testGlob, (err, files) => {
    if (JSON.stringify(files.sort()) !== JSON.stringify(testFiles)) {
      console.log('karma test files changed, restarting webpack watcher')
      process.exit()
    }
  })
})

// restart when a node package is installed otherwise bugs out
chokidar.watch(lockFile, {persistent: false}).on('all', async (event, path) => {
  if (event === 'change' || event === 'unlink') {
    console.log('lock file changed, restarting webpack watcher')
    process.exit()
  }
})