helper: file_exist (in sass-extension)

core/lib/compass/core/sass_extensions/functions.rb

@@ -11,7 +11,7 @@ def declare(*args)
   inline_image image_size constants gradient_support
   font_files   lists      colors    math
   env          cross_browser_support configuration
-  files
+  files        file_exist
 ).each do |func|
   require "compass/core/sass_extensions/functions/#{func}"
 end
@@ -33,6 +33,7 @@ module Sass::Script::Functions
   include Compass::Core::SassExtensions::Functions::Math
   include Compass::Core::SassExtensions::Functions::CrossBrowserSupport
   include Compass::Core::SassExtensions::Functions::Env
+  include Compass::Core::SassExtensions::Functions::FileExist
 end
 
 # Wierd that this has to be re-included to pick up sub-modules. Ruby bug?

core/lib/compass/core/sass_extensions/functions/file_exist.rb

@@ -0,0 +1,24 @@
+module Compass::SassExtensions::Functions::FileExist
+  def file_exist(image_file)
+    image_file = image_file.value # get to the string value of the literal.
+
+    # Compute the real path to the image on the file stystem if the generated_images_dir is set.
+    real_path = if Compass.configuration.images_path
+      images_path = Compass.configuration.images_path
+      if Pathname.new(images_path).relative? && Rails.present? && Rails.root.present?
+        File.join(Rails.root, "app", "assets", images_path, image_file)
+      else
+        File.join(images_path, image_file)
+      end
+    else
+      images_path = Compass.configuration.project_path
+      if Pathname.new(images_path).relative? && Rails.present? && Rails.root.present?
+        File.join(Rails.root, "public", images_path, image_file)
+      else
+        File.join(images_path, image_file)
+      end
+    end
+
+    return Sass::Script::Bool.new(File.exist?(real_path))
+  end
+end