Grunt task arguments do not work - gruntjs

Question

I'm trying to configure grunt to have 2 tasks (development and production). But for whatever reason, whenever I add an argument, the task gets run (as you will see) but there is not output/action:
module.exports = function(grunt) {
// Project configuration.
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
concat: {
dev: {
options: {
// define a string to put between each file in the concatenated output
separator: ';'
},
dist: {
// the files to concatenate
src: [
'public/js/jquery-1.10.2.min.js'
],
// the location of the resulting JS file
dest: 'public/js/aaaaa.src.js'
}
},
prod: {
options: {
// define a string to put between each file in the concatenated output
separator: ';'
},
dist: {
// the files to concatenate
src: [
'public/js/jquery-1.10.2.min.js'
],
// the location of the resulting JS file
dest: 'public/js/bbbbbb.src.js'
}
}
}
});
// Load Plugins
grunt.loadNpmTasks('grunt-contrib-concat');
// Default task(s).
grunt.registerTask('default', ['concat:dev']);
});
Output:
$ grunt
Running "concat:dev" (concat) task
Done, without errors.

Answer 1

The plugin does not support nested targets:
module.exports = function(grunt) {
// Project configuration.
grunt.initConfig({
pkg: grunt.file.readJSON('package.json'),
concat: {
dev: {
// the files to concatenate
src: [
'public/js/jquery-1.10.2.min.js'
],
// the location of the resulting JS file
dest: 'public/js/aaaaa.src.js'
},
prod: {
// the files to concatenate
src: [
'public/js/jquery-1.10.2.min.js'
],
// the location of the resulting JS file
dest: 'public/js/bbbbbb.src.js'
}
}
});
// Load Plugins
grunt.loadNpmTasks('grunt-contrib-concat');
// Default task(s).
grunt.registerTask('default', ['concat:dev']);
});