I started building a Rails 3.1 app that runs on Heroku using the Cedar stack. In this app I really want to take advantage of the Rails 3.1 Asset Pipeline. I’m using CoffeeScript, Sass, and Compass. The former two come with Rails 3.1 but I needed to add Compass myself. I used the instructions here, but used the latest version of Compass because it now works, and I added a check in the initializer to see if sass was loaded. The check in the initializer is needed because Heroku only runs with the asset gems from the Gemfile when it compiles the assets, and it only compiles the assets when a new slug is loaded. So what happened is that the Rails 3.1 initializer, sass.rb, tried setting a configuration parameter in sass when sass wasn’t loaded.

Here’s the relevant code. The asset section of my Gemfile now contains compass:

group :assets do
  gem 'sass-rails', "  ~> 3.1.0"
  gem 'coffee-rails', "~> 3.1.0"
  gem 'uglifier'
  gem 'compass'

…and I added config/initializers/sass.rb:

if Rails.configuration.respond_to?(:sass)
  Rails.configuration.sass.tap do |config|
    config.load_paths << "#{Gem.loaded_specs['compass'].full_gem_path}/frameworks/compass/stylesheets"

It uses respond_to? to see if it there is a sass configuration object.

Right now I’m using Compass to set a border radius.