rails--rails/actionpack/lib/sprockets/railtie.rb

module Sprockets
  class Railtie < Rails::Railtie
    def self.using_coffee?
      require 'coffee-script'
      defined?(CoffeeScript)
    rescue LoadError
      false
    end

    def self.using_scss?
      require 'sass'
      defined?(Sass)
    rescue LoadError
      false
    end

    config.app_generators.javascript_engine :coffee if using_coffee?
    config.app_generators.stylesheet_engine :scss   if using_scss?

    # Configure ActionController to use sprockets.
    initializer "sprockets.set_configs", :after => "action_controller.set_configs" do |app|
      ActiveSupport.on_load(:action_controller) do
        self.use_sprockets = app.config.assets.enabled
      end
    end

    # We need to configure this after initialization to ensure we collect
    # paths from all engines. This hook is invoked exactly before routes
    # are compiled.
    config.after_initialize do |app|
      assets = app.config.assets
      next unless assets.enabled

      app.assets = asset_environment(app)

      ActiveSupport.on_load(:action_view) do
        app.assets.context.instance_eval do
          include ::ActionView::Helpers::SprocketsHelper
        end
      end

      app.routes.prepend do
        mount app.assets => assets.prefix
      end

      if config.action_controller.perform_caching
        app.assets = app.assets.index
      end
    end

    protected

    def asset_environment(app)
      require "sprockets"
      assets = app.config.assets
      env = Sprockets::Environment.new(app.root.to_s)
      env.static_root = File.join(app.root.join("public"), assets.prefix)
      env.paths.concat assets.paths
      env.logger = Rails.logger
      env.js_compressor = expand_js_compressor(assets.js_compressor)
      env.css_compressor = expand_css_compressor(assets.css_compressor)
      env
    end

    def expand_js_compressor(sym)
      case sym
      when :closure
        require 'closure-compiler'
        Closure::Compiler.new
      when :uglifier
        require 'uglifier'
        Uglifier.new
      when :yui
        require 'yui/compressor'
        YUI::JavaScriptCompressor.new
      else
        sym
      end
    end

    def expand_css_compressor(sym)
      case sym
      when :scss
        require 'sass'
        compressor = Object.new
        def compressor.compress(source)
          Sass::Engine.new(source,
            :syntax => :scss, :style => :compressed
          ).render
        end
        compressor
      when :yui
        require 'yui/compressor'
        YUI::JavaScriptCompressor.new(:munge => true)
      else
        sym
      end
    end
  end
end