Everytime I run gulp anything, I get a assertion error. - Task function must be specified - gulp

Question

I'm trying to run the command below but unfortunately I run into errors.
$ gulp build
In my terminal and I get this assertion error. I've uninstalled node and NPM and reinstalled again using brew - How do I completely uninstall Node.js, and reinstall from beginning (Mac OS X) with these steps. My node version is v10.5.0 and npm version is 6.1.0.
My system is MacOS High Sierra 10.13.2
assert.js:269
throw err;
^
AssertionError [ERR_ASSERTION]: Task function must be specified
at Gulp.set [as _setTask] (bulkit/startup-kit/node_modules/undertaker/lib/set-task.js:10:3)
at Gulp.task (startup-kit/node_modules/undertaker/lib/task.js:13:8)
at Object.<anonymous>
at Module._compile (internal/modules/cjs/loader.js:702:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:713:10)
at Module.load (internal/modules/cjs/loader.js:612:32)
at tryModuleLoad (internal/modules/cjs/loader.js:551:12)
at Function.Module._load (internal/modules/cjs/loader.js:543:3)
at Module.require (internal/modules/cjs/loader.js:650:17)
at require (internal/modules/cjs/helpers.js:20:18)
package.json
{
"name": "bulkit-startup",
"version": "0.0.1",
"description": "Bulkit Startup Kit",
"main": "Gruntfile.js",
"devDependencies": {
"autoprefixer": "^6.3.6",
"browser-sync": "^2.24.5",
"gulp": "^4.0.0",
"gulp-clean": "^0.3.2",
"gulp-concat": "^2.6.0",
"gulp-postcss": "^6.1.0",
"gulp-sass": "^2.2.0",
"gulp-sourcemaps": "^1.6.0",
"jquery": "^3.3.1",
"mq4-hover-shim": "^0.3.0",
"panini": "^1.3.0",
"rimraf": "^2.5.2"
},
"engines": {
"node": ">=0.10.1"
},
"scripts": {
"start": "gulp",
"build": "gulp build"
},
"repository": {
"type": "git",
"url": "https://github.com/cssninjaStudio/bulkit.git"
},
"bugs": {
"url": "https://github.com/cssninjaStudio/bulkit/issues",
"email": "support#cssninja.io"
},
"author": "Css Ninja <hello#cssninja.io> (https://cssninja.io/themes/bulkit)",
"license": "Commercial",
"private": true,
"dependencies": {
"bulma": "^0.7.0",
"del": "^3.0.0",
"jquery-waypoints": "^2.0.5",
"jquery.counterup": "^2.1.0",
"scrollreveal": "^3.4.0",
"slick-carousel": "^1.8.1",
"wallop": "^2.4.1"
}
}
gulpfile.js
var gulp = require('gulp');
var clean = require('gulp-clean');
var sass = require('gulp-sass');
var sourcemaps = require('gulp-sourcemaps');
var postcss = require('gulp-postcss');
var autoprefixer = require('autoprefixer');
var mq4HoverShim = require('mq4-hover-shim');
var rimraf = require('rimraf').sync;
var browser = require('browser-sync');
var panini = require('panini');
var concat = require('gulp-concat');
var port = process.env.SERVER_PORT || 8080;
var nodepath = 'node_modules/';
var assetspath = 'assets/';
// Starts a BrowerSync instance
gulp.task('server', ['build'], function(){
browser.init({server: './_site', port: port});
});
// Watch files for changes
gulp.task('watch', function() {
gulp.watch('scss/**/*', ['compile-scss', browser.reload]);
gulp.watch('sass/**/*', ['compile-sass', browser.reload]);
gulp.watch('js/**/*', ['copy-js', browser.reload]);
gulp.watch('images/**/*', ['copy-images', browser.reload]);
gulp.watch('html/pages/**/*', ['compile-html']);
gulp.watch(['html/{layouts,includes,helpers,data}/**/*'], ['compile-html:reset','compile-html']);
gulp.watch(['./src/{layouts,partials,helpers,data}/**/*'], [panini.refresh]);
});
// Erases the dist folder
gulp.task('reset', function() {
rimraf('bulma/*');
rimraf('scss/*');
rimraf('assets/css/*');
rimraf('assets/fonts/*');
rimraf('images/*');
});
// Erases the dist folder
gulp.task('clean', function() {
rimraf('_site');
});
// Copy Bulma filed into Bulma development folder
gulp.task('setupBulma', function() {
//Get Bulma from node modules
gulp.src([nodepath + 'bulma/*.sass']).pipe(gulp.dest('bulma/'));
gulp.src([nodepath + 'bulma/**/*.sass']).pipe(gulp.dest('bulma/'));
});
// Copy static assets
gulp.task('copy', function() {
//Copy other external font and data assets
gulp.src(['assets/fonts/**/*']).pipe(gulp.dest('_site/assets/fonts/'));
gulp.src([nodepath + 'slick-carousel/slick/fonts/**/*']).pipe(gulp.dest('_site/assets/css/fonts/'));
gulp.src([nodepath + 'slick-carousel/slick/ajax-loader.gif']).pipe(gulp.dest('_site/assets/css/'));
});
//Theme Sass variables
var sassOptions = {
errLogToConsole: true,
outputStyle: 'compressed',
includePaths: [nodepath + 'bulma/sass']
};
//Theme Scss variables
var scssOptions = {
errLogToConsole: true,
outputStyle: 'compressed',
includePaths: ['./scss/partials']
};
// Compile Bulma Sass
gulp.task('compile-sass', function () {
var processors = [
mq4HoverShim.postprocessorFor({ hoverSelectorPrefix: '.is-true-hover ' }),
autoprefixer({
browsers: [
"Chrome >= 45",
"Firefox ESR",
"Edge >= 12",
"Explorer >= 10",
"iOS >= 9",
"Safari >= 9",
"Android >= 4.4",
"Opera >= 30"
]
})//,
//cssnano(),
];
//Watch me get Sassy
return gulp.src('./bulma/bulma.sass')
.pipe(sourcemaps.init())
.pipe(sass(sassOptions).on('error', sass.logError))
.pipe(postcss(processors))
.pipe(sourcemaps.write())
.pipe(gulp.dest('./_site/assets/css/'));
});
// Compile Theme Scss
gulp.task('compile-scss', function () {
var processors = [
mq4HoverShim.postprocessorFor({ hoverSelectorPrefix: '.is-true-hover ' }),
autoprefixer({
browsers: [
"Chrome >= 45",
"Firefox ESR",
"Edge >= 12",
"Explorer >= 10",
"iOS >= 9",
"Safari >= 9",
"Android >= 4.4",
"Opera >= 30"
]
})//,
//cssnano(),
];
//Watch me get Sassy
return gulp.src('./scss/core.scss')
.pipe(sourcemaps.init())
.pipe(sass(sassOptions).on('error', sass.logError))
.pipe(postcss(processors))
.pipe(sourcemaps.write())
.pipe(gulp.dest('./_site/assets/css/'));
});
// Compile Html
gulp.task('compile-html', function() {
gulp.src('html/pages/**/*.html')
.pipe(panini({
root: 'html/pages/',
layouts: 'html/layouts/',
partials: 'html/includes/',
helpers: 'html/helpers/',
data: 'html/data/'
}))
.pipe(gulp.dest('_site'))
.on('finish', browser.reload);
});
gulp.task('compile-html:reset', function(done) {
panini.refresh();
done();
});
// Compile css from node modules
gulp.task('compile-css', function() {
return gulp.src([
nodepath + 'slick-carousel/slick/slick.css',
nodepath + 'slick-carousel/slick/slick-theme.css',
nodepath + 'wallop/css/wallop.css',
//Additional static css assets
assetspath + 'css/icons.min.css',
])
.pipe(concat('app.css'))
.pipe(gulp.dest('./_site/assets/css/'));
});
// Compile js from node modules
gulp.task('compile-js', function() {
return gulp.src([
nodepath + 'jquery/dist/jquery.min.js',
nodepath + 'slick-carousel/slick/slick.min.js',
nodepath + 'scrollreveal/dist/scrollreveal.min.js',
nodepath + 'waypoints/lib/jquery.waypoints.min.js',
nodepath + 'waypoints/lib/shortcuts/sticky.min.js',
nodepath + 'jquery.counterup/jquery.counterup.min.js',
nodepath + 'wallop/js/Wallop.min.js',
//Additional static js assets
assetspath + 'js/ggpopover/ggpopover.min.js',
assetspath + 'js/ggpopover/ggtooltip.js',
assetspath + 'js/embed/embed.js',
assetspath + 'js/gmap/gmap.min.js',
])
.pipe(concat('app.js'))
.pipe(gulp.dest('./_site/assets/js/'));
});
//Copy Theme js to production site
gulp.task('copy-js', function() {
gulp.src('js/**/*.js')
.pipe(gulp.dest('./_site/assets/js/'));
});
//Copy images to production site
gulp.task('copy-images', function() {
gulp.src('images/**/*')
.pipe(gulp.dest('./_site/assets/images/'));
});
gulp.task('init', ['setupBulma']);
gulp.task('build', ['clean','copy', 'compile-js', 'compile-css', 'copy-js', 'compile-sass', 'compile-scss', 'compile-html', 'copy-images']);
gulp.task('default', ['server', 'watch']);

Answer 1

Gulp 4.0 has changed the way that tasks should be defined if the task depends on another task to execute. The list parameter has been deprecated.
An example from your gulpfile.js would be:
// Starts a BrowerSync instance
gulp.task('server', ['build'], function(){
browser.init({server: './_site', port: port});
});
Instead of the list parameter they have introduced gulp.series() and gulp.parallel().
This task should be changed to something like this:
// Starts a BrowerSync instance
gulp.task('server', gulp.series('build', function(){
browser.init({server: './_site', port: port});
}));
I'm not an expert in this. You can see a more robust example in the gulp documentation for running tasks in series or these following excellent blog posts by Jhey Thompkins and Stefan Baumgartner
https://codeburst.io/switching-to-gulp-4-0-271ae63530c0
https://fettblog.eu/gulp-4-parallel-and-series/

Answer 2

Try replacing your last line of gulpfile.js
gulp.task('default', ['server', 'watch']);
with
gulp.task('default', gulp.series('server', 'watch'));

Answer 3

Lower your gulp version in package.json file to 3.9.1-
"gulp": "^3.9.1",

Answer 4

You don't need to downgrade your gulp from gulp 4. Use gulp.series() to combine multiple tasks. At first install gulp globally with
npm install --global gulp-cli
and then install locally on your working directory with
npm install --save-dev gulp
see details here
Example:
package.json
{
"name": "gulp-test",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"devDependencies": {
"browser-sync": "^2.26.3",
"gulp": "^4.0.0",
"gulp-sass": "^4.0.2"
},
"dependencies": {
"bootstrap": "^4.3.1",
"jquery": "^3.3.1",
"popper.js": "^1.14.7"
}
}
gulpfile.js
var gulp = require("gulp");
var sass = require('gulp-sass');
var browserSync = require('browser-sync').create();
// Specific Task
function js() {
return gulp
.src(['node_modules/bootstrap/dist/js/bootstrap.min.js', 'node_modules/jquery/dist/jquery.min.js', 'node_modules/popper.js/dist/umd/popper.min.js'])
.pipe(gulp.dest('src/js'))
.pipe(browserSync.stream());
}
gulp.task(js);
// Specific Task
function gulpSass() {
return gulp
.src(['src/scss/*.scss'])
.pipe(sass())
.pipe(gulp.dest('src/css'))
.pipe(browserSync.stream());
}
gulp.task(gulpSass);
// Run multiple tasks
gulp.task('start', gulp.series(js, gulpSass));
Run gulp start to fire multiple tasks & run gulp js or gulp gulpSass for specific task.

Answer 5

https://fettblog.eu/gulp-4-parallel-and-series/
Because
gulp.task(name, deps, func) was replaced by gulp.task(name, gulp.{series|parallel}(deps, func)).
You are using the latest version of gulp but older code. Modify the code or downgrade.

Answer 6

I get the same error when using Gulp. The solution is to switch to Gulp version 3.9.1, both for the local version and the CLI version.
sudo npm install -g gulp#3.9.1
Run in the project's folder
npm install gulp#3.9.1

Answer 7

The problem is that you are using gulp 4 and the syntax in gulfile.js is of gulp 3. So either downgrade your gulp to 3.x.x or make use of gulp 4 syntaxes.
Syntax Gulp 3:
gulp.task('default', ['sass'], function() {....} );
Syntax Gulp 4:
gulp.task('default', gulp.series(sass), function() {....} );
You can read more about gulp and gulp tasks on:
https://medium.com/#sudoanushil/how-to-write-gulp-tasks-ce1b1b7a7e81

Answer 8

Replace the array in:
gulp.task('default', ['task1', 'task2','task3']);
with gulp.series()
gulp.task('default', gulp.series('task1', 'task2','task3'));

Answer 9

It's not good to keep changing the gulp & npm versions in-order to fix the errors. I was getting several exceptions last days after reinstall my working machine. And wasted tons of minutes to re-install & fixing those.
So, I decided to upgrade all to latest versions:
npm -v : v12.13.0
node -v : 6.13.0
gulp -v : CLI version: 2.2.0 Local version: 4.0.2
This error is getting because of the how it has coded in you gulpfile but not the version mismatch.
So, Here you have to change 2 things in the gulpfile to aligned with Gulp version 4.
Gulp 4 has changed how initiate the task than Version 3.
In version 4, you have to defined the task as a function, before call it as a gulp task by it's string name. In V3:
gulp.task('serve', ['sass'], function() {..});
But in V4 it should be like:
function serve() {
...
}
gulp.task('serve', gulp.series(sass));
As #Arthur has mentioned, you need to change the way of passing arguments to the task function. It was like this in V3:
gulp.task('serve', ['sass'], function() {
...
});
But in V4, it should be:
gulp.task('serve', gulp.series(sass));

Answer 10

While migrating from Gulp 3.x to Gulp 4.x, these are the common errors we are getting:
Errors:
AssertionError [ERR_ASSERTION]: Task function must be specified
AssertionError [ERR_ASSERTION]: Task never defined:
The following tasks did not complete: Did you forget to signal async completion?
Here are few points to take care regarding task definition and execution:
First define task
Use return
Then execute with gulp.series()
Here, is the quick Gulp code which is working with Gulp v4:
// First define task with Return
gulp.task('css-minify', function () {
return gulp.src('assets/images/*.*')
.pipe(smushit({verbose: true}))
.pipe(gulp.dest('assets/images'));
});
// Then execute task with bracket '()' instead of '[]'
gulp.task('default', gulp.series('css-minify'));

Answer 11

Replacing [] with gulp.series() definitely worked to me, and another change I've needed to do was to move my main task 'Ex. gulp main-task' to the end of the Gulp file using Gulp v4.02

Answer 12

worked after updating gulp.task() with gulp.task( gulp.series() );

Answer 13

Steps:
"gulp": "^3.9.1",
npm install
gulp styles