SASS (asset) path/url functions patch to make sure non absolute /assets URLs are returned (e.g. for bootstrap-sass)

assets.rb

if File.basename($0) == 'rake' && ARGV.include?('assets:precompile') # Rails.env.production?

  puts "patching sass functions to return relative asset paths" if $VERBOSE

  begin
    require 'sprockets/sass/functions'
    sass_functions = Sprockets::Sass::Functions
    Autoload::Sass::Script rescue nil # loading
  rescue LoadError # 2.x
    require 'sprockets/sass_functions'
    sass_functions = Sprockets::SassFunctions
  end

  sass_functions.module_eval do

    # relativize path - called from sass (assuming a flat public/assets structure) :
    # e.g. src:url("/assets/glyphicons-halflings-regular-xxx.eot") will end up
    #   as src:url("glyphicons-halflings-regular-xxx.eot")

    # NOTE: currently this likely won't work for target assets not on assets.paths
    # ... or when an (including) asset that ends up in the /assets sub-directory !

    %w{ image_path font_path audio_path video_path javascript_path stylesheet_path }.each do |method|
      class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def #{method}(source, options = {})
          asset_prefix = Rails.application.config.assets.prefix
          path = sprockets_context.font_path(source.value)
          ::Sass::Script::String.new(path.sub(File.join(asset_prefix, '/'), ''), :string)
        end
      RUBY
    end

    %w{ image_url font_url audio_url video_url javascript_url stylesheet_url }.each do |method|
      class_eval <<-RUBY, __FILE__, __LINE__ + 1
        def #{method}(source, options = {})
          asset_prefix = Rails.application.config.assets.prefix
          path = sprockets_context.font_path(source.value)
          ::Sass::Script::String.new("url(" + path.sub(File.join(asset_prefix, '/'), '') + ")")
        end
      RUBY
    end

  end
end