Modular Grunt.js config

alias.json

{
  "production": [
    "task:production",
    "uninstalled:production"
  ],
  "development": [
    "task"
  ]
}

grunt-contrib-task.js

var path = require('path');

module.exports = {
  task: {
    development: {
      options: {
        path: [ '.tmp', '<%= pkg.app %>' ]
      }
    },
    production: {
      options: {
        path: path.resolve('./path/to.js')
      }
    }
  }
};

Gruntfile.js

'use strict';

var path = require('path'),
    fs = require('fs'),
    matchdep = require('matchdep');

module.exports = function (grunt) {
  var gruntConfig = {
    pgk: grunt.file.readJSON('package.json');
  };

  // load all installed grunt tasks
  matchdep.filterDev('grunt-*').forEach(function(name){
    // create file path to task config with the same name
    var gruntTaskFile = path.resolve('grunt/' + name + '.js');

    // load the task
    grunt.loadNpmTasks(name);

    // check if config file exists
    if(fs.existsSync(gruntTaskFile)) {
      // load config file
      var taskConfig = require(gruntTaskFile);
      for(var task in taskConfig){
        if(taskConfig.hasOwnProperty(task)){
          // add the tasks to the final config object
          gruntConfig[task] = taskConfig[task];
        }
      }
    }
  });

  // load the combined config object
  grunt.initConfig(gruntConfig);

  var gruntTasks = grunt.file.readJSON('grunt/tasks.json');

  // Filter tasks of uninstalled packages off the tasks.json object
  // and register the alias tasks
  function filterTaskList() {
    // loop through config object with format { "aliasTaskName": [ "taskName" ] } 
    for(var aliasTaskName in gruntTasks) {
      if(gruntTasks.hasOwnProperty(aliasTask)) {
        var aliasTaskList = gruntTasks[aliasTaskName],
            out = [];

        for(var index in aliasTaskList){
          if(aliasTaskList.hasOwnProperty(index)) {
            var taskString = aliasTaskList[index],
                // extract task name from taskString with format 'task:targets:args'
                taskName = taskString.split(':')[0];

            if(grunt.config.data[taskName] !== undefined || aliasTaskList[taskName] !== undefined){
              out.push(taskString);
            }
          }
        }
        grunt.registerTask(aliasTaskName, out);
      }
    }
  }
  filterTaskList();
};