Referring to Grunt targets resulting in Warning: Object true has no method 'indexOf'

Question

My Code:

'use strict';
module.exports = function(grunt) {

    // Project configuration.
    grunt.initConfig({
        pkg: grunt.file.readJSON('package.json'),

        //Define paths
        js_src_path:    'webapp/js',
        js_build_path:  'webapp/js',
        css_src_path:   'webapp/css',
        css_build_path: 'webapp/css',
        less_src_path:  'webapp/less',
        less_build_path:'webapp/less',
//Convert Less to CSS and minify if compress = true
        less: {
            development: {
                options: {
                    path: ['<%= less_src_path %>'],
                },
                files: {
                    //'<%= less_build_path %>/app.css':'<%= concat.less.dest %>',
                    //Dynamic expansion 1:1 
                    expand: true,
                    cwd:    '<%= less_src_path %>',
                    dest:   '<%= less_build_path %>',
                    src:    '*.less',
                    ext:    '.less.css'
                }
            },
            production: {
                options: {
                    path: ['<%= less_src_path %>'],
                    //compress: true 
                    yuicompress: true
                },
                files: {
                    //'<%= less_build_path %>/app.css':'<%= concat.less.dest %>',
                    //Dynamic expansion 1:1 
                    expand: true,
                    cwd:    '<%= less_src_path %>',
                    dest:   '<%= less_build_path %>',
                    src:    '*.less',
                    ext:    '.less.min.css'
                }
            }
        }
    });

    // Load the plugin that provides the tasks.
    grunt.loadNpmTasks('grunt-lib-contrib');
    grunt.loadNpmTasks('grunt-contrib-less');

    // Task(s).
    grunt.registerTask('les', ['less']);
    grunt.registerTask('proless', ['less:production']);
    grunt.registerTask('devless', ['less:devevelopment']);
};

Running each of the following:

grunt les
grunt proless
grunt devless

Results in:

Warning: Object true has no method 'indexOf' Use --force to continue

If I remove the task development:{ ... } and production: { .... } and leave the interior and just change my les call to hit less it works fine.

Answer 1

I ran into a similar problem with contrib-concat. I think it's a syntax error on both our parts.

Try adding an array literal around your development target's "files" property, like so:

files: [{
    //'<%= less_build_path %>/app.css':'<%= concat.less.dest %>',
    //Dynamic expansion 1:1
    expand: true,
    cwd:    '<%= less_src_path %>',
    dest:   '<%= less_build_path %>',
    src:    '*.less',
    ext:    '.less.css'
}]

Here's the doc: http://gruntjs.com/configuring-tasks#building-the-files-object-dynamically

Hope that helps!