From cec1e4e40fdacc7a1ccd87381ce8c991b299c596 Mon Sep 17 00:00:00 2001
From: Rich Cavanaugh <rich@withoutscope.com>
Date: Fri, 15 Aug 2008 21:49:22 -0400
Subject: [PATCH] Overrode alias_attribute in the Dirty module to allow for the dirty tracking to work on aliased attributes.

---
 activerecord/lib/active_record/dirty.rb |   19 +++++++++++++++++--
 activerecord/test/cases/dirty_test.rb   |   13 +++++++++++++
 activerecord/test/models/parrot.rb      |    1 +
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/activerecord/lib/active_record/dirty.rb b/activerecord/lib/active_record/dirty.rb
index 63bf8c8..9cb32cd 100644
--- a/activerecord/lib/active_record/dirty.rb
+++ b/activerecord/lib/active_record/dirty.rb
@@ -34,8 +34,10 @@ module ActiveRecord
   #   person.name << 'by'
   #   person.name_change    # => ['uncle bob', 'uncle bobby']
   module Dirty
+    DIRTY_SUFFIXES = ['_changed?', '_change', '_will_change!', '_was']
+    
     def self.included(base)
-      base.attribute_method_suffix '_changed?', '_change', '_will_change!', '_was'
+      base.attribute_method_suffix *DIRTY_SUFFIXES
       base.alias_method_chain :write_attribute, :dirty
       base.alias_method_chain :save,            :dirty
       base.alias_method_chain :save!,           :dirty
@@ -44,6 +46,9 @@ module ActiveRecord
 
       base.superclass_delegating_accessor :partial_updates
       base.partial_updates = true
+      
+      base.send(:extend, ClassMethods)
+      base.metaclass.alias_method_chain(:alias_attribute, :dirty)
     end
 
     # Do any attributes have unsaved changes?
@@ -157,6 +162,16 @@ module ActiveRecord
 
         old != value
       end
-
+    
+    module ClassMethods
+      def alias_attribute_with_dirty(new_name, old_name)
+        alias_attribute_without_dirty(new_name, old_name)
+        DIRTY_SUFFIXES.each do |suffix|
+          module_eval <<-STR, __FILE__, __LINE__+1
+            def #{new_name}#{suffix}; self.#{old_name}#{suffix}; end
+          STR
+        end
+      end
+    end
   end
 end
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index feb47a1..821195f 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -45,6 +45,19 @@ class DirtyTest < ActiveRecord::TestCase
     assert_nil pirate.catchphrase_change
   end
 
+  def test_aliased_attribute_changes
+    # the actual attribute here is name, title is an
+    # alias setup via alias_attribute
+    parrot = Parrot.new
+    assert !parrot.title_changed?
+    assert_nil parrot.title_change
+    
+    parrot.name = 'Sam'
+    assert parrot.title_changed?
+    assert_nil parrot.title_was
+    assert_equal parrot.name_change, parrot.title_change
+  end
+  
   def test_nullable_integer_not_marked_as_changed_if_new_value_is_blank
     pirate = Pirate.new
 
diff --git a/activerecord/test/models/parrot.rb b/activerecord/test/models/parrot.rb
index 65191c1..b9431fd 100644
--- a/activerecord/test/models/parrot.rb
+++ b/activerecord/test/models/parrot.rb
@@ -3,6 +3,7 @@ class Parrot < ActiveRecord::Base
   has_and_belongs_to_many :pirates
   has_and_belongs_to_many :treasures
   has_many :loots, :as => :looter
+  alias_attribute :title, :name
 end
 
 class LiveParrot < Parrot
-- 
1.5.6.2