Added a rake task to compile js for non Asset Pipeline users

Gemfile

@@ -26,7 +26,7 @@ group :development, :test do
   gem 'haml',           '~> 3.1.1', :require => false
   gem 'yard'
   gem 'rdiscount' # For yard
-  gem "guard-sprockets"
+  gem "sprockets"
   gem 'rails-i18n' # Gives us default i18n for many languages
 end
 

app/assets/javascripts/active_admin/application.js

@@ -0,0 +1,4 @@
+//= require_tree  ./lib/
+//= require_tree  ./components/
+//= require_tree  ./pages/
+//= require_directory ./

app/assets/javascripts/active_admin/base.js

@@ -2,7 +2,4 @@
 //= require jquery-ui
 //= require jquery_ujs
 
-//= require_tree  ./lib/
-//= require_tree  ./components/
-//= require_tree  ./pages/
-//= require_directory ./
+//= require active_admin/application

lib/generators/active_admin/assets/assets_generator.rb

@@ -20,7 +20,7 @@ def install_assets
           template '3.1/active_admin.js', 'app/assets/javascripts/active_admin.js'
           template '3.1/active_admin.css.scss', 'app/assets/stylesheets/active_admin.css.scss'
         else
-          template '../../../../../app/assets/javascripts/active_admin/application.js', 'public/javascripts/active_admin.js'
+          template '3.0/active_admin.js', 'public/javascripts/active_admin.js'
           directory '../../../../../app/assets/images/active_admin', 'public/images/active_admin'
           generate "jquery:install --ui" if options.jquery?
           install_bourbon if options.bourbon?

tasks/js.rake

@@ -0,0 +1,32 @@
+namespace :js do
+
+  desc "Compile the JS for Rails apps without Asset Pipeline"
+  task :compile do
+    require 'sprockets'
+    require 'uglifier'
+    require 'fileutils'
+
+    root_dir = File.expand_path(File.join("..", ".."), __FILE__)
+    js_dir = File.join(root_dir, "app", "assets", "javascripts", "active_admin")
+    generated_file = File.join(root_dir, 'lib', 'generators', 'active_admin', 'assets', 'templates', '3.0', 'active_admin.js')
+
+    # The base.js file requires jquery. We don't need jquery to
+    # compile the assets, however Sprockets will try to look it up
+    # and raise an exception. Insteaad, we move the file out of the directory
+    # then put it back after we compile.
+    base_js = File.join(js_dir, "base.js")
+    tmp_base_js = File.join(root_dir, "base.js")
+    FileUtils.mv base_js, tmp_base_js
+
+    env = Sprockets::Environment.new
+    env.js_compressor = ::Uglifier.new
+    env.append_path js_dir
+
+    File.open generated_file, "w+" do |f|
+      f << env["application"]
+    end
+
+    FileUtils.mv tmp_base_js, base_js
+  end
+
+end