Signal async completion warning upon upgrade to Gulp 4

Question

I use Gulp to run one simple task in a non-JavaScript project. I'm trying to upgrade from 3.9.1 to 4.0 to get rid of the flood of "deprecated" and "security" warnings. Together with articles like A quick guide for switching to gulp 4 I've upgraded locally, dropped gulp-util and ended up with this package.json:

{
  "name": "redacted",
  "main": "gulpfile.js",
  "private": true,
  "devDependencies": {
    "ansi-colors": "^3.0.5",
    "fancy-log": "^1.3.2",
    "gulp": "^4.0.0",
    "gulp-zip": "^4.2.0",
    "temp": "^0.8.3"
  }
}

But I'm not a Node.js expert and I'm clearly missing something. My old style tasks:

var gulp = require('gulp');
var log = require('fancy-log');
gulp.task('hi', function() {
    log('Hello, World!');
});

… trigger:

PS D:\Redacted> gulp hi
[10:25:58] Using gulpfile D:\Redacted\gulpfile.js
[10:25:58] Starting 'hi'...
[10:25:58] Hello, World!
[10:25:58] The following tasks did not complete: hi
[10:25:58] Did you forget to signal async completion?

If I inject gulp.series() and get rid of anonymous functions as the article recommends:

function hi() {
    log('Hello, World!');
}
gulp.task('hi', gulp.series(hi));

… then either the task runs twice or its output gets displayed twice (not sure) but the warning persists:

PS D:\Redacted> gulp hi
[10:28:47] Using gulpfile D:\Redacted\gulpfile.js
[10:28:47] Starting 'hi'...
[10:28:47] Starting 'hi'...
[10:28:47] Hello, World!
[10:28:47] The following tasks did not complete: hi, hi
[10:28:47] Did you forget to signal async completion?

What bit am I missing? Is there a better upgrade guide?

Answer 1

The old-fashioned syntax still works. I was apparently just missing a final call to the done callback that didn't seem to be required on Gulp/3:

gulp.task('hi', function(done){
    log('Hello, World!');
    done();
});

gulp.series() looks like overkill for running a single task.