gulpfile.babel.js

'use strict';
const gulp = require('gulp');
const babel = require('gulp-babel');
const plumber = require('gulp-plumber');
const gulpIf = require('gulp-if');
const del = require('del');
const lazypipe = require('lazypipe');
const runSequence = require('run-sequence');
const merge = require('merge-stream');

var watching = false;

const transpile = lazypipe()
  .pipe(babel);

gulp.task('clean', () => {
  return del(['generators/**/*', './test/**/*']);
});

gulp.task('babel', () => {
  let generators = gulp.src(['src/generators/**/*.js'])
  .pipe(gulpIf(watching, plumber()))
    .pipe(transpile())
    .pipe(gulp.dest('generators'));

  let test = gulp.src(['src/test/**/*.js'])
  .pipe(gulpIf(watching, plumber()))
    .pipe(transpile())
    .pipe(gulp.dest('test'));

  return merge(generators, test);
});

gulp.task('watch', () => {
  watching = true;
  return gulp.watch('src/**/*.js', ['babel']);
});

gulp.task('copy', () => {
  let nonJsGen = gulp.src(['src/generators/**/*', '!src/generators/**/*.js'], {dot: true})
    .pipe(gulp.dest('generators'));

  let nonJsTest = gulp.src(['src/test/**/*', '!src/test/**/*.js'], {dot: true})
    .pipe(gulp.dest('test'));

  return merge(nonJsGen, nonJsTest);
});

gulp.task('build', cb => {
  return runSequence(
    'clean',
    'babel',
    'copy',
    cb
  );
});