How to loop through an array and run a Grunt task

Question

I have an array similar to the following:

var themes = grunt.option('themes') || [
    'theme1',
    'theme2',
    'theme3'
];

And another variable:

var theme = grunt.option('theme') || 'theme1';

This value is used in various places in my grunt file for things such as determining the path to some assets etc.

To cut a long story short, I run the following command to compile the assets for a single theme:

grunt compile --theme=theme2

I'm looking for a way to loop through the array of themes and run the compile grunt task with the appropriate grunt.option. Essentially, what I'm looking to achieve would be the equivalent of this:

grunt compile --theme=theme1 && grunt compile --theme=theme2 && grunt compile --theme=theme3

I have tried the following:

grunt.registerTask('compile:all', function() {
    themes.forEach(function(currentTheme) {
        grunt.option('theme', currentTheme);
        grunt.task.run('compile');
    });
});

This runs the compile task the appropriate number of times, but the theme option doesn't seem to get set. So my Scss files get generated, but they are empty.

I've also tried this:

grunt.registerTask('compile:all', function() {
    themes.forEach(function(currentTheme) {
        grunt.util.spawn({
            grunt : true,
            args  : ['compile', '--theme=' + currentTheme]
        });
    });
});

The task finishes almost instantly with a "success" message, but it doesn't appear to do anything.

The last thing I've tried is similar to the above, except I attempt to use async:

grunt.registerTask('compile:all', function() {
    themes.forEach(function(currentTheme) {
        var done = grunt.task.current.async();
        grunt.util.spawn({
            grunt : true,
            args  : ['compile', '--theme=' + currentTheme]
        }, done);
    });
});

But this task fails. I'm not really sure where I'm going wrong,

Thanks for any help

Answer 1

If you want to use the forEach method to build out a series of tasks, push the tasks to a task array instead of running within the forEach block:

grunt.registerTask('buildAll', function() {
    var tasks = [];
    themes.forEach(function(currentTheme) {
        tasks.push('compile:' + currentTheme);
    });

    grunt.tasks.run(tasks);
});

Within your compile task, you can pass currentTheme to the task using this.args[0] for normal tasks, or this.target for multitasks:

grunt.registerTask('compile', function() {
    var theme = this.args[0];  // sets local variable for use within task.
    grunt.option('theme', this.args[0]);  //sets option that can be referenced within this instance of `compile` 
});

Answer 2

I think your problem is that your individual compile tasks are getting queued-up by grunt.task.run('compile');, but, by the time they execute, your themes.forEach loop has completed and your theme option is set to the last value in themes.

I think you will need to register a separate task that is responsible for setting the theme option and running the compile task.

grunt.registerTask('compile_theme', function (theme) {
    grunt.option('theme', theme);
    grunt.task.run('compile');
});

You would enqueue this task within your compile:all task for each of your themes:

themes.forEach(function(currentTheme) {
    grunt.task.run('compile_theme:' + currentTheme);
});

If you want to be able to specify at the command-line which themes to compile, you would need to update your compile:all task to read all --theme= parameters and enforce that the value is an array:

grunt.registerTask('compile:all', function () {
    var compileThemes = grunt.option('theme') || 'theme1';

    if (grunt.util.kindOf(compileThemes) === 'string') {
        compileThemes = [compileThemes];
    }

    compileThemes.forEach(function(currentTheme) {
        grunt.task.run('compile_theme:' + currentTheme);
    });
});

You would call the command as follows:

grunt compile:all // compiles 'theme1'
grunt compile:all --theme=theme2 // compiles 'theme2'
grunt compile:all --theme=theme2 --theme=theme3 // compiles 'theme2' and 'theme3'

Note: You would probably want to rename your compile:all task at this point because it no longer necessarily compiles all themes.

EDIT

It is not working because we are expecting too much of the theme option. We are trying to use this to get the themes entered at the command-line and to compose values dynamically in our configuration (like, dest: theme + '/app.js'. With the way I have structured my answer, theme cannot be used in the configuration.

I would instead use a configuration variable for theme that will be used in the config. This would mean updating the compile_theme task:

grunt.registerTask('compile_theme', function (theme) {
    grunt.config('theme', theme);
    grunt.task.run('compile');
});

We would need to update our configuration by substituting template strings for theme. For example:

dest: '<%= theme %>/app.js'

Answer 3

Using for each never worked for me, but this did based off of this help doc from grunt: https://gruntjs.com/creating-tasks#multi-tasks

I added the list to my initConfig, ie

grunt.initConfig({
    run_themes: {
        theme1: 'sdi',
        theme2: 'syd',
        theme3: 'phl'
    }});

Then:

//register task to loop through the themes
grunt.task.registerMultiTask('run_themes', 'Compile themes.', function() {
    //grunt.themes.writeln(this.target + ': ' + this.data);
    grunt.log.writeln(this.target + ': ' + this.data);
    grunt.option('theme', this.data);
    grunt.task.run('sass');
});

And my sass definition makes use of grunt.option('theme') like this to put a copy of the same compiled css in each theme directory like sdi/default/... syd/default... phl/default...

// compile our sass to css
sass: {
    // sass compilation for "dev", unminified files
    dev: {
        options: {
            style: 'expanded'
        },
        files: [{
            expand: true,
            cwd:'shared-resources/css/sass',
            src: ['*.scss', 'standalone/*.scss'],
            dest: "../<%= grunt.option('theme') %>/default/template-resources/css/dev",
            ext: '.css'
        }]
    }},