Gulp 4.0 signal async completion error despite returning stream

Question

I have the following gulp task that returns a stream. It works fine in gulp 3.9.1, but converting to gulp 4.0, I get:

Did you forget to signal async completion?

const gulp = require('gulp');
const gulpif = require('gulp-if');
const plumber = require('gulp-plumber');
const rename = require('gulp-rename');
const buffer = require('vinyl-buffer');
const es = require('event-stream');
const browserify = require('browserify');
const browserifyInc = require('browserify-incremental');
const babelify = require('babelify');
const browserSync = require('browser-sync').create();

// Incrementally building the js
gulp.task('build-js-inc', () =>
  es.merge.apply(null, paths.entry.scripts.map(script => {
    const b = browserify(Object.assign({}, browserifyInc.args,
      {
        entries: script,
        extensions: ['.jsx'],
        debug: true
      }
    ));

    browserifyInc(b, { cacheFile: './browserify-cache.json' });

    return b.transform(babelify)
      .bundle()
        .on('error', handleErrors)
        .pipe(source(`./${script.split('/')[script.split('/').length - 1]}`))
        .pipe(buffer())
        .pipe(plumber())
        .pipe(rename(path => {
          path.extname = '.bundle.js';
        }))
        .pipe(gulp.dest('public/js'))
        .pipe(gulpif('*sw.bundle.js', gulp.dest('public')))
        .pipe(browserSync.reload({ stream: true }));
  }))
);

I've tried adding done() to my upstream tasks, but it still errors because I'm thinking it originates here and propogates through my subsequent tasks that rely on this one finishing.

Answer 1

The problem ended up being the module event-stream. Apparently it is no longer being maintained.

@phated:

Support for event-stream is deprecated. Everything is supposed to move to through2, et al. Maybe just fully deprecate this module?

I switched to merge-stream and now my gulpfile works fine.