Fix destroying belongs_to associations for CPK

activerecord/lib/active_record/autosave_association.rb

@@ -501,7 +501,8 @@ def save_belongs_to_association(reflection)
           autosave = reflection.options[:autosave]
 
           if autosave && record.marked_for_destruction?
-            self[reflection.foreign_key] = nil
+            foreign_key = Array(reflection.foreign_key)
+            foreign_key.each { |key| self[key] = nil }
             record.destroy
           elsif autosave != false
             saved = record.save(validate: !autosave) if record.new_record? || (autosave && record.changed_for_autosave?)

activerecord/test/cases/autosave_association_test.rb

@@ -1028,6 +1028,18 @@ def test_should_destroy_a_parent_association_as_part_of_the_save_transaction_if_
     assert_nil Pirate.find_by_id(id)
   end
 
+  # belongs_to for CPK
+  def test_autosave_cpk_association_should_destroy_parent_association_when_marked_for_destruction
+    book = Cpk::Book.new(title: "Book", author_id: 1, number: 2)
+    Cpk::Order.create!(id: [3, 4], book: book)
+
+    book.order.mark_for_destruction
+
+    assert book.save
+    assert_nil book.reload.order
+    assert_nil Cpk::Order.find_by(id: 4, shop_id: 3)
+  end
+
   def test_should_skip_validation_on_a_parent_association_if_marked_for_destruction
     @ship.pirate.catchphrase = ""
     assert_not_predicate @ship, :valid?

activerecord/test/models/cpk/book.rb

@@ -5,6 +5,7 @@ class Book < ActiveRecord::Base
     self.table_name = :cpk_books
     self.primary_key = [:author_id, :number]
 
+    belongs_to :order, autosave: true, query_constraints: [:shop_id, :order_id]
     belongs_to :author, class_name: "Cpk::Author"
   end