Added #to_i to DateTime in ActiveSupport so #to_yaml works correctly on...

Added #to_i to DateTime in ActiveSupport so #to_yaml works correctly on ActiveRecord models with DateTime attributes.

activerecord/test/cases/yaml_serialization_test.rb

+require "cases/helper"
+require 'models/topic'
+
+class YamlSerializationTest < ActiveRecord::TestCase
+  def test_to_yaml_with_time_with_zone_should_not_raise_exception
+    Time.zone = ActiveSupport::TimeZone["Pacific Time (US & Canada)"]
+    ActiveRecord::Base.time_zone_aware_attributes = true
+    topic = Topic.new(:written_on => DateTime.now)
+    assert_nothing_raised { topic.to_yaml }
+  end
+end

activesupport/lib/active_support/core_ext/date_time/conversions.rb

@@ -78,7 +78,18 @@ def xmlschema
   
   # Converts self to a floating-point number of seconds since the Unix epoch 
   def to_f
-    days_since_unix_epoch = self - ::DateTime.civil(1970)
-    (days_since_unix_epoch * 86_400).to_f
+    seconds_since_unix_epoch.to_f
+  end
+
+  # Converts self to an integer number of seconds since the Unix epoch
+  def to_i
+    seconds_since_unix_epoch.to_i
+  end
+
+  private
+
+  def seconds_since_unix_epoch
+    seconds_per_day = 86_400
+    (self - ::DateTime.civil(1970)) * seconds_per_day
   end
 end

activesupport/test/core_ext/date_time_ext_test.rb

@@ -350,6 +350,10 @@ def test_to_f
     assert_equal 946684800.0, DateTime.civil(1999,12,31,19,0,0,Rational(-5,24)).to_f
   end
 
+  def test_to_i
+    assert_equal 946684800, DateTime.civil(2000).to_i
+  end
+
   protected
     def with_env_tz(new_tz = 'US/Eastern')
       old_tz, ENV['TZ'] = ENV['TZ'], new_tz