compass.rb

# Extension in my Rails lib dir
require 'lib/extensions/sass_widget_image_url'

# This configuration file works with both the Compass command line tool and within Rails.

project_type = :rails

# Require any additional compass plugins here.
require 'susy'

# HTTP paths
http_path = "/"
http_stylesheets_path = "/stylesheets"
http_images_path = "/images"
http_javascripts_path = "/javascripts"

# File system locations
sass_dir = "app/assets/stylesheets"
css_dir = "public/stylesheets"
images_dir = "public/images"
javascripts_dir = "public/javascripts"

# Set to true for easier debugging
line_comments = false

# CSS output style - :nested, :expanded, :compact, or :compressed
output_style = :nested

# To enable relative paths to assets via compass helper functions. Uncomment:
relative_assets = true

# If you prefer the indented syntax, you might want to regenerate this
# project again passing --syntax sass, or you can uncomment this:
preferred_syntax = :sass

# Disable the asset cache buster:
asset_cache_buster :none

# Learn more:
#   http://compass-style.org/help/tutorials/configuration-reference/

gistfile1.txt

# Running compass compile generates this:
$ compass compile
Nothing to compile. If you're trying to start a new project, you have left off the directory argument.
Run "compass -h" to get help.

# If I remove the line from the config file and just try it on the command line I get this:
$ compass compile -r lib/extensions/sass_widget_image_url.rb
LoadError on line ["161"] of /Users/jlong/.rvm/gems/ruby-1.9.3-p286-perf@uservoice/gems/compass-0.12.2/lib/compass/configuration/data.rb: cannot load such file -- lib/extensions/sass_widget_image_url.rb
Run with --trace to see the full backtrace

sass_widget_image_url.rb

module SassWidgetImageUrl
  def widget_image_url(path)
    Sass::Script::String.new("url(//#{WIDGET2_DOMAIN}/images/#{path.value})")
  end
end

module Sass::Script::Functions
  include SassWidgetImageUrl
end