Save has_one associations only if record has changes

Prevents save related callbacks such as `after_commit` being
triggered when `has_one` objects are already persisted and have no
changes.

1 files changed, 15 insertions, 0 deletions

diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 517d2674a7..acb19032ea 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -626,10 +626,25 @@ class TestDestroyAsPartOfAutosaveAssociation < ActiveRecord::TestCase
       end
     end
 
+    @ship.pirate.catchphrase = "Changed Catchphrase"
+
     assert_raise(RuntimeError) { assert !@pirate.save }
     assert_not_nil @pirate.reload.ship
   end
 
+  def test_should_save_changed_has_one_changed_object_if_child_is_saved
+    @pirate.ship.name = "NewName"
+    @pirate.ship.expects(:save).once.returns(true)
+
+    assert @pirate.save
+  end
+
+  def test_should_not_save_changed_has_one_unchanged_object_if_child_is_saved
+    @pirate.ship.expects(:save).never
+
+    assert @pirate.save
+  end
+
   # belongs_to
   def test_should_destroy_a_parent_association_as_part_of_the_save_transaction_if_it_was_marked_for_destroyal
     assert !@ship.pirate.marked_for_destruction?