Allow for the dirty tracking to work with the aliased name of aliased attributes.

Signed-off-by: Michael Koziarski <michael@koziarski.com>
[#812 state:committed]

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 +46,8 @@ module ActiveRecord
 
       base.superclass_delegating_accessor :partial_updates
       base.partial_updates = true
+
+      base.send(:extend, ClassMethods)
     end
 
     # Do any attributes have unsaved changes?
@@ -161,5 +165,19 @@ module ActiveRecord
         old != value
       end
 
+    module ClassMethods
+      def self.extended(base)
+        base.metaclass.alias_method_chain(:alias_attribute, :dirty)
+      end
+
+      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

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
 

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