gulp 4.0 simplified with child_process spawn

gulpfile.js

'use strict'

require('./backend/extensions')

let gulp = require('gulp'),
  argv = require('yargs').argv,
  del = require('del'),
  $ = require('gulp-load-plugins')(),
  spawn = require('child_process').spawn,
  os = require('os'),
  path = require('path'),
  osCMD = os.platform() === 'win32' ? '.cmd' : '',
  APP_NAME = require('./backend/config/config').APP_NAME,
  INSTANCES =  require('./backend/config/config').INSTANCES,
  entry = `./backend/${APP_NAME}.js`

let paths = {
  frontend: './frontend',
  backend: './backend',
  dist: './dist'
}

function getShellCmd(cliName, args) {
  let cmd = path.resolve('./node_modules/.bin/' + cliName + osCMD)
  return spawn(cmd, args)
}

function gulpShellCmd(done, cliName, args, steamRoll){
  let cmd = getShellCmd(cliName, args)

  cmd.stderr.pipe(process.stderr)

  cmd.stdout.on('data', (data) => $.util.log(String(data)));

  ['close', 'exit', 'error'].forEach((listName) => {
    if(steamRoll){
      return cmd.on(listName, () => done())
    }
    cmd.on(listName, done)
  })
}

let gsc = gulpShellCmd

function lint(done, doWatch, toWatch) {
  // easy way to interact with CLI of esw
  // (learned from inside of esw on how it interacts with eslint)
  toWatch = toWatch || ['./backend/*.js', './backend/**/*.js']

  if (doWatch)
    toWatch.push('-w')

  gsc(done, 'esw', toWatch)

}

gulp.task('lint', (done) => lint(done))

gulp.task('lint:watch', (done) => lint(done, true))

gulp.task('serve', (done) => {
    let args = []
    if(argv.debug)
      args.push('--debug')
    args.push(entry)
    gsc(done, 'nodemon', args)
})

gulp.task('serve:prod', (done) => gsc(done, 'pm2', ['start', '-i', INSTANCES, entry]))

gulp.task('assets', (done) => gsc(done, 'webpack', ['--progress', '-c', '-w']))

gulp.task('assets:prod', (done) => gsc(done, 'webpack', ['-p', '--config', 'webpack.production.js']))

gulp.task('clean', (done) => {
  del([paths.dist, '*.log']).then(() => done()).catch((err) => done(err))
})

gulp.task('html', () => {
  return gulp.src(`${paths.frontend}/*.html`)
    .pipe(gulp.dest(paths.dist))
})

gulp.task('default', gulp.series('clean', gulp.parallel('html', 'assets', 'lint:watch', 'serve')))