cypress/cli/lib/exec/spawn.js

const _ = require('lodash')
const cp = require('child_process')
const Promise = require('bluebird')
const debug = require('debug')('cypress:cli')

const downloadUtils = require('../download/utils')
const xvfb = require('./xvfb')
const { throwDetailedError, errors } = require('../errors')

module.exports = {
  start (args, options = {}) {
    args = [].concat(args)

    _.defaults(options, {
      verify: false,
      detached: false,
      stdio: [process.stdin, process.stdout, 'ignore'],
    })

    const spawn = () => {
      return new Promise((resolve, reject) => {
        const cypressPath = downloadUtils.getPathToExecutable()
        debug('spawning Cypress %s', cypressPath)
        debug('args %j', args)
        debug('some of the options %j', _.pick(options, ['verify', 'detached']))

        const child = cp.spawn(cypressPath, args, options)
        child.on('exit', resolve)
        child.on('error', reject)

        if (options.detached) {
          child.unref()
        }
      })
    }

    const userFriendlySpawn = () =>
      spawn().catch(throwDetailedError(errors.unexpected))

    const needsXvfb = xvfb.isNeeded()
    if (needsXvfb) {
      return xvfb.start()
      .then(userFriendlySpawn)
      .finally(xvfb.stop)
    } else {
      return userFriendlySpawn()
    }
  },
}