title: Gulp watch - not working
body: <p>I have gulpfile.js from <a href="https://github.com/gulpjs/gulp" rel="nofollow noreferrer">https://github.com/gulpjs/gulp</a>.
  I just change folders name for mine. 
  Task 'gulp' work normally, first 'gulp watch' too. But any another save any less file don't do anything. Just "Finished 'styles' after 1.34 s"
  (JS works good)</p>
  
  <p>Any advice?
  main.less have less imports with all filles
  Folders looks like:</p>
  
  <pre><code>/www
      /js
      /css
          main.less
          file.less
          file2.less
          /lib
              file3.less
  
  
  
  
  var gulp = require('gulp');
  var less = require('gulp-less');
  var babel = require('gulp-babel');
  var concat = require('gulp-concat');
  var uglify = require('gulp-uglify');
  var rename = require('gulp-rename');
  var cleanCSS = require('gulp-clean-css');
  var del = require('del');
  
  var paths = {
      styles: {
          src: 'www/css/main.less',
          dest: 'www/css/'
      },
      scripts: {
          src: 'www/js/js/**/*.js',
          dest: 'www/js/'
      }
  };
  
  function clean() {
    return del([ 'assets' ]);
  }
  
  function styles() {
    return gulp.src(paths.styles.src)
      .pipe(less())
      .pipe(cleanCSS())
      // pass in options to the stream
      .pipe(rename({
        basename: 'main',
        suffix: '.min'
      }))
      .pipe(gulp.dest(paths.styles.dest));
  }
  
  function scripts() {
    return gulp.src(paths.scripts.src, { sourcemaps: true})
      .pipe(babel())
      .pipe(uglify())
      .pipe(concat('all.min.js'))
      .pipe(gulp.dest(paths.scripts.dest));
  }
  
  function watch() {
    gulp.watch("www/js/js**/*.js", scripts);
    gulp.watch("www/css/**/*.less", styles);
  }
  
  exports.clean = clean;
  exports.styles = styles;
  exports.scripts = scripts;
  exports.watch = watch;
  
  var build = gulp.series(clean, gulp.parallel(styles, scripts));
  
  gulp.task('build', build);
  
  gulp.task('default', build);
  </code></pre>