pulsar/script/lib/backup-node-modules.js

const fs = require('fs-extra')
const path = require('path')

module.exports = function (packagePath) {
  const nodeModulesPath = path.join(packagePath, 'node_modules')
  const nodeModulesBackupPath = path.join(packagePath, 'node_modules.bak')

  if (fs.existsSync(nodeModulesBackupPath)) {
    throw new Error('Cannot back up ' + nodeModulesPath + '; ' + nodeModulesBackupPath + ' already exists')
  }

  // some packages may have no node_modules after deduping, but we still want
  // to "back-up" and later restore that fact
  if (!fs.existsSync(nodeModulesPath)) {
    const msg = 'Skipping backing up ' + nodeModulesPath + ' as it does not exist'
    console.log(msg.gray)

    const restore = function stubRestoreNodeModules () {
      if (fs.existsSync(nodeModulesPath)) {
        fs.removeSync(nodeModulesPath)
      }
    }

    return {restore, nodeModulesPath, nodeModulesBackupPath}
  }

  fs.copySync(nodeModulesPath, nodeModulesBackupPath)

  const restore = function restoreNodeModules () {
    if (!fs.existsSync(nodeModulesBackupPath)) {
      throw new Error('Cannot restore ' + nodeModulesPath + '; ' + nodeModulesBackupPath + ' does not exist')
    }

    if (fs.existsSync(nodeModulesPath)) {
      fs.removeSync(nodeModulesPath)
    }
    fs.renameSync(nodeModulesBackupPath, nodeModulesPath)
  }

  return {restore, nodeModulesPath, nodeModulesBackupPath}
}