uppy/bin/build-lib.js

const chalk = require('chalk')
const babel = require('@babel/core')
const { promisify } = require('util')
const glob = promisify(require('glob'))
const mkdirp = promisify(require('mkdirp'))
const fs = require('fs')
const path = require('path')

const transformFile = promisify(babel.transformFile)
const writeFile = promisify(fs.writeFile)
const stat = promisify(fs.stat)

const SOURCE = 'packages/{*,@uppy/*}/src/**/*.js'
// Files not to build (such as tests)
const IGNORE = /\.test\.js$|__mocks__|companion\//
// Files that should trigger a rebuild of everything on change
const META_FILES = [
  'babel.config.js',
  'package.json',
  'package-lock.json',
  'bin/build-lib.js'
]

function lastModified (file) {
  return stat(file).then((s) => s.mtime)
}

async function buildLib () {
  const metaMtimes = await Promise.all(META_FILES.map((filename) =>
    lastModified(path.join(__dirname, '..', filename))
  ))
  const metaMtime = Math.max(...metaMtimes)

  const files = await glob(SOURCE)
  for (const file of files) {
    if (IGNORE.test(file)) continue
    const libFile = file.replace('/src/', '/lib/')

    // on a fresh build, rebuild everything.
    if (!process.env.FRESH) {
      const srcMtime = await lastModified(file)
      const libMtime = await lastModified(libFile)
        .catch(() => 0) // probably doesn't exist
      // Skip files that haven't changed
      if (srcMtime < libMtime && metaMtime < libMtime) {
        continue
      }
    }

    const { code, map } = await transformFile(file, { sourceMaps: true })
    await mkdirp(path.dirname(libFile))
    await Promise.all([
      writeFile(libFile, code),
      writeFile(libFile + '.map', JSON.stringify(map))
    ])
    console.log(chalk.green('Compiled lib:'), chalk.magenta(libFile))
  }
}

console.log('Using Babel version:', require('@babel/core/package.json').version)
buildLib().catch((err) => {
  console.error(err.stack)
  process.exit(1)
})