Using Sprockets 2 in Rails 3.0.x with CoffeeScript & SASS

0_instructions.md

Some brief instructions on how to use Sprocket 2 in Rails to get CoffeeScript powered JS and SASS powered CSS with YUI compression all via the magic of rack.

This stuff will be native in Rails 3.1 and the layout of the files on the filesystem will be different but this guide will get you working with it while we wait for all that to finalize.

Ignore the number prefixes on each file. This is just to ensure proper order in the Gist.

Note from suranyami:

I had issues with sprockets (2.0.0.beta.13) because the paths array was being duplicated and returned, so adding things to it did nothing.

Instead use:

append_path 'javascripts'
append_path 'stylesheets'

in the AssetServer class.

I have also created a simple example Rails 3 app at:

https://github.com/suranyami/sprocket_sample

1_Gemfile.rb

gem 'coffee-script'
gem 'yui-compressor', :require => 'yui/compressor'
gem 'sass'
gem 'json' # sprocket dependency for Ruby 1.8 only
gem 'sprockets', :git => 'git://github.com/sstephenson/sprockets.git'

2_asset_server.rb

# Config a Sprockets::Environment to mount as a Rack end-point. I like to use a subclass
# as it allows the config to be easily reusable. Since I use the same instance for
# all mount points I make it a singleton class. I just add this as an initializer to my
# project since it is really just configuration.

class AssetServer < Sprockets::Environment
  include Singleton

  def initialize
    super Rails.public_path
    append_path 'javascripts'
    append_path 'stylesheets'
    if Rails.env.production?
      self.js_compressor = YUI::JavaScriptCompressor.new :munge => true, :optimize => true
      self.css_compressor = YUI::CssCompressor.new
    end
  end

end

3_routes.rb

# Mount the rack end-point for JavaScript and CSS.
MyApp::Application.routes.draw do
  mount AssetServer.instance => 'javascripts'
  mount AssetServer.instance => 'stylesheets'
end

4_application.js.coffee

# Put this in your
#     public/javascripts
# directory and call:
#         <%= javascript_include_tag 'application' %>
# in your browser

alert 'hello world'

5_application.css.scss

// Put this in your
//     public/stylesheets
// directory and call:
//         <%= stylesheet_link_tag 'application' %>
// in your browser

h1 {color: red}
body {margin: 2px + 5px}

6_conclusion.txt

Sprockets 2 has a lot more under the hood but this gets you started.

A few things not covered:

1. Anything supported by Tilt can be used as a template engine
   (not just Sass and CoffeeScript).
2. Although Sass has native abilities to include other files, Sprockets 2
   gives the ability to all formats through special comments like:
     // =require "foo"
   It's special commands can be fairly powerful (like requiring an entire
   directory or tree). NOTE: Use the comment character relevant for the
   language. So coffescript should be:
     # =require 'foo.js'
   Then you can create 'foo.js.coffee' and when served it will be as one
   file.
3. Sprockets 2 has the ability to pre-compile the assets for maximum speed.
   Also useful when the deployment environment doesn't support a template
   language (like CoffeeScript).