atom/build/lib/transpile-babel-paths.js

'use strict'

const babel = require('babel-core')
const fs = require('fs')
const glob = require('glob')
const path = require('path')

const CONFIG = require('../config')
const BABEL_OPTIONS = require('../../static/babelrc.json')
const BABEL_PREFIXES = [
  "'use babel'",
  '"use babel"',
  '/** @babel */',
  '/* @flow */'
]
const PREFIX_LENGTH = Math.max.apply(null, BABEL_PREFIXES.map(prefix => prefix.length))
const BUFFER = Buffer(PREFIX_LENGTH)

module.exports = function () {
  console.log(`Transpiling Babel paths in ${CONFIG.intermediateAppPath}...`);
  for (let path of getPathsToTranspile()) {
    if (usesBabel(path)) {
      transpileBabelPath(path)
    }
  }
}

function getPathsToTranspile () {
  let paths = []
  paths = paths.concat(glob.sync(path.join(CONFIG.intermediateAppPath, 'src', '**', '*.js')))
  for (let packageName of Object.keys(CONFIG.appMetadata.packageDependencies)) {
    paths = paths.concat(glob.sync(
      path.join(CONFIG.intermediateAppPath, 'node_modules', packageName, '**', '*.js'),
      {ignore: path.join(CONFIG.intermediateAppPath, 'node_modules', packageName, 'spec', '**', '*.js')}
    ))
  }
  return paths
}

function usesBabel (path) {
  const file = fs.openSync(path, 'r')
  fs.readSync(file, BUFFER, 0, PREFIX_LENGTH)
  fs.closeSync(file)
  const filePrefix = BUFFER.toString('utf8', 0, PREFIX_LENGTH).trim()
  return BABEL_PREFIXES.indexOf(filePrefix) !== -1
}

function transpileBabelPath (path) {
  const options = Object.assign({}, BABEL_OPTIONS)
  options.sourceMap = null
  fs.writeFileSync(path, babel.transformFileSync(path, options).code)
}