Revert "Remove update_attribute."

This reverts commit a7f4b0a1231bf3c65db2ad4066da78c3da5ffb01.

Conflicts:
	activerecord/lib/active_record/associations/has_one_association.rb
	activerecord/lib/active_record/persistence.rb
	activerecord/test/cases/base_test.rb
	activerecord/test/cases/dirty_test.rb
	activerecord/test/cases/timestamp_test.rb

2 files changed, 51 insertions, 1 deletions

diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index 92677b9926..9a2a5a4e3c 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -509,6 +509,16 @@ class DirtyTest < ActiveRecord::TestCase
     assert_not_nil pirate.previous_changes['updated_on'][1]
     assert !pirate.previous_changes.key?('parrot_id')
     assert !pirate.previous_changes.key?('created_on')
+
+    pirate = Pirate.find_by_catchphrase("Ahoy!")
+    pirate.update_attribute(:catchphrase, "Ninjas suck!")
+
+    assert_equal 2, pirate.previous_changes.size
+    assert_equal ["Ahoy!", "Ninjas suck!"], pirate.previous_changes['catchphrase']
+    assert_not_nil pirate.previous_changes['updated_on'][0]
+    assert_not_nil pirate.previous_changes['updated_on'][1]
+    assert !pirate.previous_changes.key?('parrot_id')
+    assert !pirate.previous_changes.key?('created_on')
   end
 
   if ActiveRecord::Base.connection.supports_migrations?
@@ -534,7 +544,7 @@ class DirtyTest < ActiveRecord::TestCase
 
       pirate = target.create(:created_on => created_on)
       pirate.reload # Here mysql truncate the usec value to 0
-      
+
       pirate.created_on = created_on
       assert !pirate.created_on_changed?
     end
diff --git a/activerecord/test/cases/persistence_test.rb b/activerecord/test/cases/persistence_test.rb
index 72b8219782..4ffa4836e0 100644
--- a/activerecord/test/cases/persistence_test.rb
+++ b/activerecord/test/cases/persistence_test.rb
@@ -371,10 +371,50 @@ class PersistencesTest < ActiveRecord::TestCase
     assert_raise(ActiveSupport::FrozenObjectError) { client.name = "something else" }
   end
 
+  def test_update_attribute
+    assert !Topic.find(1).approved?
+    Topic.find(1).update_attribute("approved", true)
+    assert Topic.find(1).approved?
+
+    Topic.find(1).update_attribute(:approved, false)
+    assert !Topic.find(1).approved?
+  end
+
   def test_update_attribute_does_not_choke_on_nil
     assert Topic.find(1).update_attributes(nil)
   end
 
+  def test_update_attribute_for_readonly_attribute
+    minivan = Minivan.find('m1')
+    assert_raises(ActiveRecord::ActiveRecordError) { minivan.update_attribute(:color, 'black') }
+  end
+
+  def test_update_attribute_with_one_updated
+    t = Topic.first
+    t.update_attribute(:title, 'super_title')
+    assert_equal 'super_title', t.title
+    assert !t.changed?, "topic should not have changed"
+    assert !t.title_changed?, "title should not have changed"
+    assert_nil t.title_change, 'title change should be nil'
+
+    t.reload
+    assert_equal 'super_title', t.title
+  end
+
+  def test_update_attribute_for_updated_at_on
+    developer = Developer.find(1)
+    prev_month = Time.now.prev_month
+
+    developer.update_attribute(:updated_at, prev_month)
+    assert_equal prev_month, developer.updated_at
+
+    developer.update_attribute(:salary, 80001)
+    assert_not_equal prev_month, developer.updated_at
+
+    developer.reload
+    assert_not_equal prev_month, developer.updated_at
+  end
+
   def test_update_column
     topic = Topic.find(1)
     topic.update_column("approved", true)