serve *.sass using Rack::File

sass_stylesheets.rb

# app/metal/sass_stylesheets.rb
#
# This Rails metal keeps Sass stylesheets up-to-date, and serves them using Rack.
#
# Unlike the default Sass/Rails integration, this happily supports a 
# Sass::Plugin.options[:css_location] outside the Rails.public_path.
#
class SassStylesheets

  class << self

    def call(env)
      Sass::Plugin.check_for_updates
      sass_file_server.call(env)
    end

    private

    def sass_file_server
      stylesheets_dir = Sass::Plugin.options[:css_location]
      @sass_file_server ||= ::Rack::File.new(File.dirname(stylesheets_dir))
    end

  end

end