Merge pull request #9141 from adamgamble/issue-9091

belongs_to :touch should touch old record when transitioning.

4 files changed, 62 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c6ce77a9cc..438064a403 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -598,6 +598,28 @@
     *Aaron Stone + Rafael Mendonça França*
 
 *   `Relation#merge` now only overwrites where values on the LHS of the
+=======
+*   Belongs_to :touch behavior now touches old association when
+    transitioning to new association
+
+        class Passenger < ActiveRecord::Base
+           belongs_to :car, touch: true
+        end
+
+        car_1 = Car.create
+        car_2 = Car.create
+
+        passenger = Passenger.create :car => car_1
+
+        passenger.car = car_2
+        passenger.save
+
+    Previously only car_2 would be touched. Now both car_1 and car_2
+    will be touched.
+
+    *Adam Gamble*
+
+*   Relation#merge now only overwrites where values on the LHS of the
     merge. Consider:
 
         left  = Person.where(age: [13, 14, 15])
diff --git a/activerecord/lib/active_record/associations/builder/belongs_to.rb b/activerecord/lib/active_record/associations/builder/belongs_to.rb
index 9ac561b997..579d7789bd 100644
--- a/activerecord/lib/active_record/associations/builder/belongs_to.rb
+++ b/activerecord/lib/active_record/associations/builder/belongs_to.rb
@@ -68,6 +68,16 @@ module ActiveRecord::Associations::Builder
         def belongs_to_touch_after_save_or_destroy_for_#{name}
           record = #{name}
 
+          foreign_key_field   = #{reflection.foreign_key}
+          if changed_attributes.key?(foreign_key_field)
+            reflection_klass  = #{reflection.klass}
+            old_foreign_id    = changed_attributes[foreign_key_field]
+            old_record        = reflection_klass.where(foreign_key_field.to_sym => old_foreign_id).first
+            if old_record
+              old_record.touch #{options[:touch].inspect if options[:touch] != true}
+            end
+          end
+
           unless record.nil? || record.new_record?
             record.touch #{options[:touch].inspect if options[:touch] != true}
           end
diff --git a/activerecord/test/cases/timestamp_test.rb b/activerecord/test/cases/timestamp_test.rb
index 777a2b70dd..0c13bb946a 100644
--- a/activerecord/test/cases/timestamp_test.rb
+++ b/activerecord/test/cases/timestamp_test.rb
@@ -176,6 +176,32 @@ class TimestampTest < ActiveRecord::TestCase
     assert_not_equal time, owner.updated_at
   end
 
+  def test_changing_parent_of_a_record_touches_both_new_and_old_parent_record
+    klass = Class.new(ActiveRecord::Base) do
+      def self.name; 'Toy'; end
+      belongs_to :pet, touch: true
+    end
+
+    toy1 = klass.find(1)
+    old_pet = toy1.pet
+
+    toy2 = klass.find(2)
+    new_pet = toy2.pet
+    time = 3.days.ago
+
+    old_pet.update_columns(updated_at: time)
+    new_pet.update_columns(updated_at: time)
+
+    toy1.pet = new_pet
+    toy1.save!
+
+    old_pet.reload
+    new_pet.reload
+
+    assert_not_equal time, new_pet.updated_at
+    assert_not_equal time, old_pet.updated_at
+  end
+
   def test_timestamp_attributes_for_create
     toy = Toy.first
     assert_equal toy.send(:timestamp_attributes_for_create), [:created_at, :created_on]
diff --git a/activerecord/test/fixtures/toys.yml b/activerecord/test/fixtures/toys.yml
index 037e335e0a..07ed75e98e 100644
--- a/activerecord/test/fixtures/toys.yml
+++ b/activerecord/test/fixtures/toys.yml
@@ -2,3 +2,7 @@ bone:
   toy_id: 1
   name: Bone
   pet_id: 1
+doll:
+  toy_id: 2
+  name: Doll
+  pet_id: 2