1 files changed, 38 insertions, 27 deletions

diff --git a/activerecord/lib/active_record/timestamp.rb b/activerecord/lib/active_record/timestamp.rb
index 5531d12a41..1511c71ffc 100644
--- a/activerecord/lib/active_record/timestamp.rb
+++ b/activerecord/lib/active_record/timestamp.rb
@@ -1,72 +1,83 @@
+require 'active_support/core_ext/class/attribute'
+
 module ActiveRecord
   # = Active Record Timestamp
-  # 
+  #
   # Active Record automatically timestamps create and update operations if the
-  # table has fields named <tt>created_at/created_on</tt> or 
+  # table has fields named <tt>created_at/created_on</tt> or
   # <tt>updated_at/updated_on</tt>.
   #
   # Timestamping can be turned off by setting:
   #
-  #   <tt>ActiveRecord::Base.record_timestamps = false</tt>
+  #   config.active_record.record_timestamps = false
   #
   # Timestamps are in the local timezone by default but you can use UTC by setting:
   #
-  #   <tt>ActiveRecord::Base.default_timezone = :utc</tt>
+  #   config.active_record.default_timezone = :utc
   #
   # == Time Zone aware attributes
   #
   # By default, ActiveRecord::Base keeps all the datetime columns time zone aware by executing following code.
   #
-  #   ActiveRecord::Base.time_zone_aware_attributes = true
+  #   config.active_record.time_zone_aware_attributes = true
   #
   # This feature can easily be turned off by assigning value <tt>false</tt> .
   #
-  # If your attributes are time zone aware and you desire to skip time zone conversion for certain 
-  # attributes then you can do following:
+  # If your attributes are time zone aware and you desire to skip time zone conversion to the current Time.zone
+  # when reading certain attributes then you can do following:
   #
-  #   Topic.skip_time_zone_conversion_for_attributes = [:written_on]
+  #   class Topic < ActiveRecord::Base
+  #     self.skip_time_zone_conversion_for_attributes = [:written_on]
+  #   end
   module Timestamp
     extend ActiveSupport::Concern
 
     included do
-      class_inheritable_accessor :record_timestamps, :instance_writer => false
+      class_attribute :record_timestamps, :instance_writer => false
       self.record_timestamps = true
     end
 
   private
 
     def create #:nodoc:
-      if record_timestamps
+      if self.record_timestamps
         current_time = current_time_from_proper_timezone
 
-        timestamp_attributes_for_create.each do |column|
+        all_timestamp_attributes.each do |column|
           write_attribute(column.to_s, current_time) if respond_to?(column) && self.send(column).nil?
         end
-
-        timestamp_attributes_for_update_in_model.each do |column|
-          write_attribute(column.to_s, current_time) if self.send(column).nil?
-        end
       end
 
       super
     end
 
     def update(*args) #:nodoc:
-      record_update_timestamps if !partial_updates? || changed?
+      if should_record_timestamps?
+        current_time = current_time_from_proper_timezone
+
+        timestamp_attributes_for_update_in_model.each do |column|
+          column = column.to_s
+          next if attribute_changed?(column)
+          write_attribute(column, current_time)
+        end
+      end
       super
     end
 
-    def record_update_timestamps #:nodoc:
-      return unless record_timestamps
-      current_time = current_time_from_proper_timezone
-      timestamp_attributes_for_update_in_model.inject({}) do |hash, column|
-        hash[column.to_s] = write_attribute(column.to_s, current_time)
-        hash
-      end
+    def should_record_timestamps?
+      self.record_timestamps && (!partial_updates? || changed? || (attributes.keys & self.class.serialized_attributes.keys).present?)
+    end
+
+    def timestamp_attributes_for_create_in_model
+      timestamp_attributes_for_create.select { |c| self.class.column_names.include?(c.to_s) }
+    end
+
+    def timestamp_attributes_for_update_in_model
+      timestamp_attributes_for_update.select { |c| self.class.column_names.include?(c.to_s) }
     end
 
-    def timestamp_attributes_for_update_in_model #:nodoc:
-      timestamp_attributes_for_update.select { |elem| respond_to?(elem) }
+    def all_timestamp_attributes_in_model
+      timestamp_attributes_for_create_in_model + timestamp_attributes_for_update_in_model
     end
 
     def timestamp_attributes_for_update #:nodoc:
@@ -78,9 +89,9 @@ module ActiveRecord
     end
 
     def all_timestamp_attributes #:nodoc:
-      timestamp_attributes_for_update + timestamp_attributes_for_create
+      timestamp_attributes_for_create + timestamp_attributes_for_update
     end
-    
+
     def current_time_from_proper_timezone #:nodoc:
       self.class.default_timezone == :utc ? Time.now.utc : Time.now
     end