Hackily fix the Rails 3 routing errors we were seeing in 3.0.11.

Closes gh-194

doc-src/HAML_CHANGELOG.md

@@ -3,6 +3,14 @@
 * Table of contents
 {:toc}
 
+## 3.0.12 (Unreleased)
+
+## Rails 3 Support
+
+Apparently the last version broke in new and exciting ways under Rails 3,
+due to the inconsistent load order caused by certain combinations of gems.
+3.0.12 hacks around that inconsistency, and *should* be fully Rails 3-compatible.
+
 ## 3.0.11
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.11).

doc-src/SASS_CHANGELOG.md

@@ -3,6 +3,14 @@
 * Table of contents
 {:toc}
 
+## 3.0.12 (Unreleased)
+
+## Rails 3 Support
+
+Apparently the last version broke in new and exciting ways under Rails 3,
+due to the inconsistent load order caused by certain combinations of gems.
+3.0.12 hacks around that inconsistency, and *should* be fully Rails 3-compatible.
+
 ## 3.0.11
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/3.0.11).

lib/sass/plugin/rails.rb

@@ -12,8 +12,17 @@ unless defined?(Sass::RAILS_LOADED)
   if defined?(ActionController::Metal)
     # Rails >= 3.0
     require 'sass/plugin/rack'
-    Rails.application.instance_variable_set('@app',
+    if Rails.application.instance_variable_get('@app')
-      Sass::Plugin::Rack.new(Rails.application.app))
+      # The application has already been built,
+      # so we need to hack the middleware in
+      Rails.application.instance_variable_set('@app',
+        Sass::Plugin::Rack.new(Rails.application.app))
+    else
+      # The application hasn't been built yet,
+      # so we can just add Sass::Plugin::Rack
+      # to the pending middleware stack.
+      Rails.configuration.middleware.use(Sass::Plugin::Rack)
+    end
   elsif defined?(ActionController::Dispatcher) &&
       defined?(ActionController::Dispatcher.middleware)
     # Rails >= 2.3