AssertionError [ERR_ASSERTION] - gulp

Question

I have gulp file that is having issues with latest update to gulp 4 I am getting assertion errors (AssertionError [ERR_ASSERTION]: Task function must be specified) and it seems (from googling) to have to do with how tasks are defined, but not sure if this is the case here and what needs to change.
Node: node -v
v14.16.0
CLI version: 2.3.0
Local version: 4.0.2
NPM: 6.14.11
Here is the code
// ### CSS processing pipeline
// Example
// ```
// gulp.src(cssFiles)
// .pipe(cssTasks('main.css')
// .pipe(gulp.dest(path.dist + 'styles'))
// ```
var cssTasks = function(filename) {
return lazypipe()
.pipe(function() {
return gulpif(!enabled.failStyleTask, plumber());
})
.pipe(function() {
return gulpif(enabled.maps, sourcemaps.init());
})
.pipe(function() {
return gulpif('*.less', less());
})
.pipe(function() {
return gulpif('*.scss', sass({
outputStyle: 'nested', // libsass doesn't support expanded yet
precision: 10,
includePaths: ['.'],
errLogToConsole: !enabled.failStyleTask
}));
})
.pipe(concat, filename)
.pipe(autoprefixer, {
browsers: [
'last 2 versions',
'android 4',
'opera 12'
]
})
.pipe(cssNano, {
safe: true
})
.pipe(function() {
return gulpif(enabled.rev, rev());
})
.pipe(function() {
return gulpif(enabled.maps, sourcemaps.write('.', {
sourceRoot: 'assets/styles/'
}));
})();
};
// ### JS processing pipeline
// Example
// ```
// gulp.src(jsFiles)
// .pipe(jsTasks('main.js')
// .pipe(gulp.dest(path.dist + 'scripts'))
// ```
var jsTasks = function(filename) {
return lazypipe()
.pipe(function() {
return gulpif(enabled.maps, sourcemaps.init());
})
.pipe(concat, filename)
.pipe(uglify, {
compress: {
'drop_debugger': enabled.stripJSDebug
}
})
.pipe(function() {
return gulpif(enabled.rev, rev());
})
.pipe(function() {
return gulpif(enabled.maps, sourcemaps.write('.', {
sourceRoot: 'assets/scripts/'
}));
})();
};
// ### Write to rev manifest
// If there are any revved files then write them to the rev manifest.
// See https://github.com/sindresorhus/gulp-rev
var writeToManifest = function(directory) {
return lazypipe()
.pipe(gulp.dest, path.dist + directory)
.pipe(browserSync.stream, {match: '**/*.{js,css}'})
.pipe(rev.manifest, revManifest, {
base: path.dist,
merge: true
})
.pipe(gulp.dest, path.dist)();
};
// ## Gulp tasks
// Run `gulp -T` for a task summary
// ### Styles
// `gulp styles` - Compiles, combines, and optimizes Bower CSS and project CSS.
// By default this task will only log a warning if a precompiler error is
// raised. If the `--production` flag is set: this task will fail outright.
gulp.task('styles', ['wiredep'], function() {
var merged = merge();
manifest.forEachDependency('css', function(dep) {
var cssTasksInstance = cssTasks(dep.name);
if (!enabled.failStyleTask) {
cssTasksInstance.on('error', function(err) {
console.error(err.message);
this.emit('end');
});
}
merged.add(gulp.src(dep.globs, {base: 'styles'})
.pipe(plumber({errorHandler: onError}))
.pipe(cssTasksInstance));
});
return merged
.pipe(writeToManifest('styles'));
});
// ### Scripts
// `gulp scripts` - Runs JSHint then compiles, combines, and optimizes Bower JS
// and project JS.
gulp.task('scripts', function() {
var merged = merge();
manifest.forEachDependency('js', function(dep) {
merged.add(
gulp.src(dep.globs, {base: 'scripts'})
.pipe(plumber({errorHandler: onError}))
.pipe(jsTasks(dep.name))
);
});
return merged
.pipe(writeToManifest('scripts'));
});
// ### Fonts
// `gulp fonts` - Grabs all the fonts and outputs them in a flattened directory
// structure. See: https://github.com/armed/gulp-flatten
gulp.task('fonts', function() {
return gulp.src(globs.fonts)
//.pipe(flatten())
.pipe(gulp.dest(path.dist + 'fonts'))
.pipe(browserSync.stream());
});
// ### Images
// `gulp images` - Run lossless compression on all the images.
gulp.task('images', function() {
return gulp.src(globs.images)
.pipe(imagemin([
imagemin.jpegtran({progressive: true}),
imagemin.gifsicle({interlaced: true}),
imagemin.svgo({plugins: [
{removeUnknownsAndDefaults: false},
{cleanupIDs: false}
]})
]))
.pipe(gulp.dest(path.dist + 'images'))
.pipe(browserSync.stream());
});
// ### JSHint
// `gulp jshint` - Lints configuration JSON and project JS.
gulp.task('jshint', function() {
return gulp.src([
'bower.json', 'gulpfile.js'
].concat(project.js))
.pipe(jshint())
.pipe(jshint.reporter('jshint-stylish'))
.pipe(gulpif(enabled.failJSHint, jshint.reporter('fail')));
});
// ### Clean
// `gulp clean` - Deletes the build folder entirely.
gulp.task('clean', require('del').bind(null, [path.dist]));
// ### Watch
// `gulp watch` - Use BrowserSync to proxy your dev server and synchronize code
// changes across devices. Specify the hostname of your dev server at
// `manifest.config.devUrl`. When a modification is made to an asset, run the
// build step for that asset and inject the changes into the page.
// See: http://www.browsersync.io
gulp.task('watch', function() {
browserSync.init({
files: ['{lib,templates}/**/*.php', '*.php'],
proxy: config.devUrl,
snippetOptions: {
whitelist: ['/wp-admin/admin-ajax.php'],
blacklist: ['/wp-admin/**']
}
});
gulp.watch([path.source + 'styles/**/*'], ['styles']);
gulp.watch([path.source + 'scripts/**/*'], ['scripts']);
gulp.watch([path.source + 'fonts/**/*'], ['fonts']);
gulp.watch([path.source + 'images/**/*'], ['images']);
gulp.watch(['bower.json', 'assets/manifest.json'], ['build']);
});
// ### Build
// `gulp build` - Run all the build tasks but don't clean up beforehand.
// Generally you should be running `gulp` instead of `gulp build`.
gulp.task('build', function(callback) {
runSequence('styles',
'scripts',
['fonts', 'images'],
callback);
});
// ### Wiredep
// `gulp wiredep` - Automatically inject Less and Sass Bower dependencies. See
// https://github.com/taptapship/wiredep
gulp.task('wiredep', function() {
var wiredep = require('wiredep').stream;
return gulp.src(project.css)
.pipe(wiredep())
.pipe(changed(path.source + 'styles', {
hasChanged: changed.compareSha1Digest
}))
.pipe(gulp.dest(path.source + 'styles'));
});
Any help is greatly appreciated.

Answer 1

So there are a few things wrong with your code.
gulp.task('styles', ['wiredep'], function() {
for example should be
gulp.task('styles', gulp.series('wiredep', function() { etc.
gulp.task only takes three arguments. You may have more places in your code like this.
gulp.watch([path.source + 'styles/**/*'], ['styles']); might actually be fine but lets be careful and make it a little more future-proof:
gulp.watch([path.source + 'styles/**/*'], gulp.series('styles'));
Etc. change all of these in your watch task.
With gulp.series and gulp.parallel you no longer need something like runSequence. So replace
gulp.task('build', function(callback) {
runSequence('styles',
'scripts',
['fonts', 'images'],
callback);
});
with
gulp.task('build', gulp.series(
'styles',
'scripts',
gulp.parallel('fonts', 'images')
// callback); // see below
);
Make these changes and you'll see if you need the `callback` in the `build` task - if you get a message about signaling async completion.
-----------
And you may have to move your `wiredep` task before your `styles` task. Since you are using `gulp.task` rather than functions to create your tasks, you cannot refer to a task that hasn't been created yet. That wouldn't be an issue if you used all named functions to create each task.