gulp-uglifyjs error when gulp.src returns no files

Question

I have a unknown number of folders inside a directory called app that I am looping through to create a folderName.min.js for each.

Gulp script:

var es = require('event-stream');
var uglify = require('gulp-uglifyjs');
var fs = require('fs');
var path = require('path');

function getFolders(dir) {
  return fs.readdirSync(dir)
    .filter(function (file) {
      return fs.statSync(path.join(dir, file)).isDirectory();
  })
}

gulp.task('js', function () {
  var folders = getFolders('./src/app/');

  var streams = folders.map(function (folder) {

    return gulp.src(folder + '**/*.js')
      .pipe(uglify(folder + '.min.js', {
        mangle: true
      }))
      .pipe(gulp.dest('./dist/js'))
  });

  return es.concat.apply(null, streams);
});

The problem I am running in to is that not every folder contains *.js files. When gulp-uglifyjs encounters this case, I get

gulp-uglifyjs - No files given; aborting minification

and the stream aborts and all subsequent tasks do not get run. Am I able to

a) tell uglifyjs to proceed anyway if it runs in to this case

b) skip the task if gulp.src returned no files?

Answer 1

The solution was to modify my getFolders function to only return folders that contained JavaScript files. I did this by walking each subdirectory inside app and checking if any *.js files were found.

function getJSFolders(dir) {
  return fs.readdirSync(dir)
    .filter(function (file) {
      var files;
      var isDir = fs.statSync(path.join(dir, file)).isDirectory();
      var hasJs = false;

      if (isDir) {
        files = getFiles(path.join(dir, file));

        for (var i = 0; i < files.length; i++) {
          if (path.extname(files[i]) === '.js') {
            hasJs = true;
            break;
          }
        }
      }

      return isDir && hasJs;
    });
}

function getFiles(dir, filesArr) {
  var files = fs.readdirSync(dir);
  filesArr = filesArr || [];

  for (var i in files) {
    if (!files.hasOwnProperty(i)) continue;
    var name = dir + '/' + files[i];
    if (fs.statSync(name).isDirectory()) {
      getFiles(name, filesArr);
    } else {
      filesArr.push(name);
    }
  }

  return filesArr;
}