Merge pull request #48491 from adrianna-chang-shopify/ac-fk-changed-f…

…or-cpk

Bugfix: Ensure has_one associations saved when part of CPK has changed

activerecord/lib/active_record/autosave_association.rb

@@ -482,7 +482,10 @@ def _record_changed?(reflection, record, key)
       def association_foreign_key_changed?(reflection, record, key)
         return false if reflection.through_reflection?
 
-        record._has_attribute?(reflection.foreign_key) && record._read_attribute(reflection.foreign_key) != key
+        foreign_key = Array(reflection.foreign_key)
+        return false unless foreign_key.all? { |key| record._has_attribute?(key) }
+
+        foreign_key.map { |key| record._read_attribute(key) } != Array(key)
       end
 
       def inverse_polymorphic_association_changed?(reflection, record)

activerecord/test/cases/associations/belongs_to_associations_test.rb

@@ -376,6 +376,16 @@ def test_belongs_to_with_inverse_association_for_composite_primary_key
     assert_equal order_id, book.order_id
   end
 
+  def test_should_set_composite_foreign_key_on_association_when_key_changes_on_associated_record
+    book = Cpk::Book.create!(id: [1, 2], title: "The Well-Grounded Rubyist")
+    order = Cpk::Order.create!(id: [1, 2], book: book)
+
+    order.shop_id = 3
+    order.save!
+
+    assert_equal 3, book.shop_id
+  end
+
   def test_building_the_belonging_object_with_implicit_sti_base_class
     account = Account.new
     company = account.build_firm