Add Promise to gulp task with forEach

Question

I have a svg-sprites gulp task looping through my Sprites. Some of them need to be minified, so I have an if running the minify task on those sprites.

I'd like it to show as finished when the forEach is finished. Right now it says "Finished" way too early. I guess I should add a promise, but I am not sure how to approach it. Help appreciated.

var gulp =        require('gulp');
var svgSprite =   require('gulp-svg-sprite');
var svgmin =      require('gulp-svgmin');

gulp.task('svg-sprites', function() {

  var stream = '';

  config.svgSprites.forEach(function (item) {

    stream = gulp.src(item.src + '/**/*.svg');

    if(item.doMinify) {
      stream.pipe(svgmin({
        plugins: [
          {
            removeAttrs: {
              attrs: ['path:fill', 'g:fill']
            }
          }
        ]
      }))
    }

    stream.pipe(svgSprite())
      .pipe(gulp.dest(normalizePath(item.dest)));
  });

  return stream;
});

Answer 1

I apparently needed to push my streams to an array of streams and merging all streams at the end, all the time "updating" my stream variable when piping. I ended up with this:

var gulp =        require('gulp');
var svgSprite =   require('gulp-svg-sprite');
var svgmin =      require('gulp-svgmin');
var merge =       require('merge-stream');

gulp.task('svg-sprites', function() {
  var streams = [];

  config.svgSprites.forEach(function (item) {
    var stream = gulp.src(item.src + '/**/*.svg');

    if(item.doMinify) {
      // "Update" stream to be a reference to the output of the task
      stream = stream.pipe(svgmin({
        plugins: [
          {
            removeAttrs: {
              attrs: ['path:fill', 'g:fill']
            }
          }
        ]
      }))
    }

    // "Update" stream to be a reference to the output of the task
    stream = stream.pipe(svgSprite()).pipe(gulp.dest(normalizePath(item.dest)));

    streams.push(stream);
  });

  return merge.apply(this, streams);
});