Support stale state detections in CPK through associations

activerecord/lib/active_record/associations/through_association.rb

@@ -81,7 +81,9 @@ def construct_join_attributes(*records)
         # to try to properly support stale-checking for nested associations.
         def stale_state
           if through_reflection.belongs_to?
-            owner[through_reflection.foreign_key] && owner[through_reflection.foreign_key].to_s
+            Array(through_reflection.foreign_key).map do |foreign_key_column|
+              owner[foreign_key_column] && owner[foreign_key_column].to_s
+            end
           end
         end
 

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -1639,6 +1639,17 @@ def test_loading_cpk_association_with_unpersisted_owner
     assert_equal([order_agreement], book.order_agreements.to_a)
   end
 
+  def test_cpk_stale_target
+    order = Cpk::Order.create!(shop_id: 1)
+    book = Cpk::BookWithOrderAgreements.create!(id: [1, 2], order: order)
+    Cpk::OrderAgreement.create!(order: order)
+
+    book.order_agreements.load
+    book.order = Cpk::Order.new
+
+    assert_predicate(book.association(:order_agreements), :stale_target?)
+  end
+
   private
     def make_model(name)
       Class.new(ActiveRecord::Base) { define_singleton_method(:name) { name } }

activerecord/test/cases/associations/has_one_through_associations_test.rb

@@ -454,4 +454,15 @@ def test_loading_cpk_association_with_unpersisted_owner
 
     assert_equal(order_agreement, book.order_agreement)
   end
+
+  def test_cpk_stale_target
+    order = Cpk::Order.create!(shop_id: 1)
+    book = Cpk::BookWithOrderAgreements.create!(id: [1, 2], order: order)
+    Cpk::OrderAgreement.create!(order: order)
+
+    book.order_agreement
+    book.order = Cpk::Order.new
+
+    assert_predicate(book.association(:order_agreement), :stale_target?)
+  end
 end