dirty.rb in mongomodel-0.2.18

- old
+ new

@@ -8,17 +8,40 @@
       included do
         before_save { @previously_changed = changes }
         after_save { changed_attributes.clear }
       end
       
+      def write_attribute(key, value)
+        attr = key.to_sym
+        
+        # The attribute already has an unsaved change.
+        if changed_attributes.include?(attr)
+          old = changed_attributes[attr]
+          changed_attributes.delete(attr) if value == old
+        else
+          old = clone_attribute_value(attr)
+          changed_attributes[attr] = old unless value == old
+        end
+        
+        super
+      end
+      
       # Returns the attributes as they were before any changes were made to the document.
       def original_attributes
         {}.with_indifferent_access.merge(attributes).merge(changed_attributes)
       end
-    
+      
     protected
       def changed_attributes
-        attributes.changed
+        @changed_attributes ||= {}.with_indifferent_access
+      end
+    
+    private
+      def clone_attribute_value(attribute_name)
+        value = self[attribute_name.to_sym]
+        value.duplicable? ? value.clone : value
+      rescue TypeError, NoMethodError
+        value
       end
     end
   end
 end