Merge pull request #38942 from joshmn/joshmn_fix_has_one_touch

Prevent has_one from touching parent record unless persisted

activerecord/CHANGELOG.md

+*   Prevent `build_association` from `touching` a parent record if the record isn't persisted for `has_one` associations.
+
+    Fixes #38219
+
+    *Josh Brody*
+    
 *   Add support for `if_not_exists` option for adding index.
 
     The `add_index` method respects `if_not_exists` option. If it is set to true

activerecord/lib/active_record/associations/has_one_association.rb

@@ -81,7 +81,9 @@ def remove_target!(method)
             target.delete
           when :destroy
             target.destroyed_by_association = reflection
-            target.destroy
+            if target.persisted?
+              target.destroy
+            end
           else
             nullify_owner_attributes(target)
             remove_inverse_instance(target)

activerecord/test/cases/associations/has_one_associations_test.rb

@@ -851,4 +851,22 @@ def test_dependency_should_halt_parent_destruction
       assert_not author.destroy
     end
   end
+
+  class SpecialCar < ActiveRecord::Base
+    self.table_name = "cars"
+    has_one :special_bulb, inverse_of: :car, dependent: :destroy, class_name: "SpecialBulb", foreign_key: "car_id"
+  end
+
+  class SpecialBulb < ActiveRecord::Base
+    self.table_name = "bulbs"
+    belongs_to :car, inverse_of: :special_bulb, touch: true, class_name: "SpecialCar"
+  end
+
+  def test_has_one_with_touch_option_on_nonpersisted_built_associations_doesnt_update_parent
+    car = SpecialCar.create(name: "honda")
+    assert_queries(1) do
+      car.build_special_bulb
+      car.build_special_bulb
+    end
+  end
 end