Raise an error if Rails.root is nil.

doc-src/HAML_CHANGELOG.md

@@ -3,6 +3,14 @@
 * Table of contents
 {:toc}
 
+## 3.0.3 (Unreleased)
+
+### Rails 3 Support
+
+In order to make some Rails loading errors easier to debug,
+Sass will now raise an error if `Rails.root` is `nil` when Sass is loading.
+Previously, this would just cause the paths to be mis-set.
+
 ## 3.0.2
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.2).

doc-src/SASS_CHANGELOG.md

@@ -5,6 +5,12 @@
 
 ## 3.0.3 (Unreleased)
 
+### Rails 3 Support
+
+In order to make some Rails loading errors easier to debug,
+Sass will now raise an error if `Rails.root` is `nil` when Sass is loading.
+Previously, this would just cause the paths to be mis-set.
+
 ### Merb Support
 
 Merb, including 1.1.0 as well as earlier versions,

lib/haml/util.rb

@@ -260,7 +260,10 @@ module Haml
     #
     # @return [String, nil]
     def rails_root
-      return Rails.root.to_s if defined?(Rails.root)
+      if defined?(Rails.root)
+        return Rails.root.to_s if Rails.root
+        raise "ERROR: Rails.root is nil!"
+      end
       return RAILS_ROOT.to_s if defined?(RAILS_ROOT)
       return nil
     end