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

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": "[email protected]"
    },
    "author": "Css Ninja <[email protected]> (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']);

Otha

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/

Gravesend

This changes my error from Task must be specified to Task never defined. – Ashtray

@Ashtray I hope you got this sorted in the end but I had the same problem until I moved the definition of the gulp.task with the series() / parallel() calls below where the tasks named there were defined. It seemed like the classic javascript error of trying to use a function before it was defined. – Alduino

@Alduino This is exactly what happened in my case, I moved the task series definition below the section where I defined my tasks and it worked. (This wasn't a problem in v3). – Bigotry

@Ashtray I moved such as task to the same file as the default task was defined inside (before it) and it solved the issue, so it's some loading order issue – Dela

If you look at the last line number mentioned in the error, e.g. [...] at Object.<anonymous> (/path/to/gulpfile.js:209:25) that tells you line 209 is the context at which the task is being referenced. If the task is not declared above this line, you'll get Task never defined. – Ingaingaberg

Answer 2

Try replacing your last line of gulpfile.js

gulp.task('default', ['server', 'watch']);

with

gulp.task('default', gulp.series('server', 'watch'));

Rebarebah

makes no difference – Sectional

Answer 3

Lower your gulp version in package.json file to 3.9.1-

"gulp": "^3.9.1",

Chicane

Don't do this if you're on Node v10. – Mallette

@Mallette could you elaborate on that, please? – Killie

@Henri Version 4 changed how tasks are run, so for his current code to work he needs to run gulp 3.9.1. But the better answer is to update his code to be compatible with gulp 4+ – Plage

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.

Alar

This was close enough. Had to check Gulp website to get the syntax right and add exports. – Tankard

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.

Auria

Answer 6

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

Rakes

Answer 7

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 [email protected]

Run in the project's folder

npm install [email protected]

Bulgarian

Answer 8

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:

1. First define task
2. Use return
3. 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'));

Beller

Answer 9

Replace the array in:

gulp.task('default', ['task1', 'task2','task3']); 

with gulp.series()

gulp.task('default', gulp.series('task1', 'task2','task3'));

Schottische

Would you mind elaborating on how this is different from this answer? – Granvillegranvillebarker

Answer 10

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.

1. 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));

2. 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));

Thousand

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

Augustus

You may need to move it around the tasks by order of definition. – Illegality

Answer 12

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

Eustoliaeutectic

Answer 13

Steps:

1. "gulp": "^3.9.1",
2. npm install
3. gulp styles

Kliment