Gulp.js event stream merge order

Question

I am trying to merge css and scss files into a main.css file that goes in my build directory. Its working, but not in the right order. The style attributes from the scss files n

Answer 1

I tried gulp-order without success: the order somehow wasn't taken into account.

The solution which worked for me was using stream-series, mentioned by Aperçu.

return streamSeries(
    cssTomincss,
    cssFromscss)
    .pipe(concat('main.css'))
    .pipe(minifyCSS())
    .pipe(gulp.dest('build/css'));

Answer 2

I failed with all provided answers, they produced some silent errors. Finally merge2 worked for me (seems like there was gulp-merge and later the project was renamed into merge2). I'm not sure why there is a need in streamify plugin, e.g. streams created with Rollup may produce "stream-not-supported-errors" with gulp-concat, gulp-uglify or gulp-insert.

const mergeStreams = require('merge2');
const streamify = require('streamify');
...
gulp.task('build', () => {
    const streams = sources.map(createJSFile);
    return mergeStreams(...streams)
        .pipe(streamify(concat('bundle.js')))
        .pipe(streamify(uglify()))
        .pipe(gulp.dest('./dist'));
});

Answer 3

It seems that the plugin gulp-order fits perfectly well in your case.

It allows you to re-order the passed stream with your own glob pattern, for example based on your code :

return es.merge(cssTomincss, cssFromscss)
    .pipe(order([
      'dev/css/reset.css',
      'dev/css/style.css',
      'dev/css/typography.css',
      'dev/css/sizes.css',
      'dev/css/*.css',
    ]))
    .pipe(concat('main.css'))
    .pipe(minifyCSS())
    .pipe(gulp.dest('build/css'))

One drawback of this is that you have to re-declare your globs, but you can get around by assign your globs to a value and then concat them in you order pipe, much cleaner.

You may have to set the base option to . of gulp-order as stated in their Readme if the files were not ordered correctly.

One another way would be to use stream-series, basically the same as event-stream, but the order of your stream is preserved, and you don't have to rewrite your globs.

Answer 4

Try streamqueue.

var streamqueue = require('streamqueue');

gulp.task('css', function () {
    return streamqueue({ objectMode: true },
            gulp.src(['dev/css/reset.css', 'dev/css/style.css', 'dev/css/typography.css', 'dev/css/sizes.css']),
            gulp.src(['dev/css/*.scss']).pipe(sass())
        )
        .pipe(concat('main.css'))
        .pipe(minifyCSS())
        .pipe(gulp.dest('build/css'))
});

This cheatsheet will help you. PDF is here.