Merge pull request rails#48363 from gmcgibbon/has_one_autosave_cpk

Fix has_one autosaving for CPK associations

Author: eileencodes

activerecord/lib/active_record/autosave_association.rb

@@ -453,7 +453,9 @@ def save_has_one_association(reflection)
 
             if (autosave && record.changed_for_autosave?) || _record_changed?(reflection, record, key)
               unless reflection.through_reflection
-                record[reflection.foreign_key] = key
+                Array(key).zip(Array(reflection.foreign_key)).each do |primary_key, foreign_key_column|
+                  record[foreign_key_column] = primary_key
+                end
                 association.set_inverse_instance(record)
               end
 

activerecord/test/cases/autosave_association_test.rb

@@ -486,6 +486,12 @@ def test_validation_does_not_validate_non_dirty_association_target
     assert_equal true, squeak.mouse.present?
     assert_equal true, squeak.valid?
   end
+
+  test "composite primary key autosave" do
+    assert_nothing_raised do
+      Cpk::Order.create!(id: [1, 2], book: Cpk::Book.new(title: "Book", author_id: 3, number: 4))
+    end
+  end
 end
 
 class TestDefaultAutosaveAssociationOnAHasManyAssociationWithAcceptsNestedAttributes < ActiveRecord::TestCase

activerecord/test/models/cpk/order.rb

@@ -7,6 +7,7 @@ class Order < ActiveRecord::Base
 
     has_many :order_agreements, primary_key: :id
     has_many :books, query_constraints: [:shop_id, :order_id]
+    has_one :book, query_constraints: [:shop_id, :order_id]
   end
 
   class BrokenOrder < Order