Task never defined: undefined - gulp

Question

I used a similar configuration to another project (with more tasks) but I'm not sure what I'm missing here to get this error:
AssertionError [ERR_ASSERTION]: Task never defined: undefined
So would like to use Gulp 4 and use 3 tasks (build HTML, minify JavaScript, and create a server). I'm dividing it into 2 processes: dev and build.
const gulp = require('gulp');
const jsmin = require('gulp-jsmin');
const browserSync = require('browser-sync').create();
function jsMinify () {
return gulp.src('./src/**/*.js')
.pipe(jsmin())
.pipe(gulp.dest('./dist'))
}
function buildHTML () {
return gulp.src('./src/html/**/*.html')
.pipe(gulp.dest('./dist'))
}
function buildServe () {
browserSync.init({
server: {
baseDir: "./dist/",
},
port: 9001
});
}
function watch (){
browserSync.init({
server: {
baseDir: "./src/",
},
port: 8080
});
gulp.watch('./src/**/*.html').on('change', browserSync.reload);
gulp.watch('./src/**/*.js').on('change', browserSync.reload);
};
const dev = gulp.series(watch);
const build = gulp.series(
gulp.parallel(buildHTML, jsMinify),
buildServe()
);
exports.dev = dev;
exports.build = build;
Am I missing something about Gulp 4 or this code should run without any issue?

Answer 1

This is an error:
const build = gulp.series(
gulp.parallel(buildHTML, jsMinify),
buildServe() // <= error here, don't call the function just list it like below
);
const build = gulp.series(
gulp.parallel(buildHTML, jsMinify),
buildServe // <= removed ()
);
gulp.series() arguments are function names or task names. By using buildServe() I imagine that it is returning undefined hence your error message about undefined never being defined as a task. I hope that makes sense.
[I haven't been able to test this change yet to see if it fixes your issue, but I don't see any other problems in your code.]