Revert singular association breaking changes

activerecord/lib/active_record/associations/has_one_association.rb

@@ -92,10 +92,6 @@ def set_new_record(record)
           replace(record, false)
         end
 
-        def replace_keys(record, force: false)
-          # Has one association doesn't have foreign keys to replace.
-        end
-
         def remove_target!(method)
           case method
           when :delete

activerecord/lib/active_record/associations/singular_association.rb

@@ -54,13 +54,11 @@ def set_new_record(record)
         end
 
         def _create_record(attributes, raise_error = false, &block)
-          reflection.klass.transaction do
-            record = build(attributes, &block)
-            saved = record.save
-            replace_keys(record, force: true)
-            raise RecordInvalid.new(record) if !saved && raise_error
-            record
-          end
+          record = build_record(attributes, &block)
+          saved = record.save
+          set_new_record(record)
+          raise RecordInvalid.new(record) if !saved && raise_error
+          record
         end
     end
   end

activerecord/test/cases/associations/has_one_associations_test.rb

@@ -20,8 +20,6 @@
 require "models/membership"
 require "models/parrot"
 require "models/cpk"
-require "models/user"
-require "models/content"
 
 class HasOneAssociationsTest < ActiveRecord::TestCase
   self.use_transactional_tests = false unless supports_savepoints?
@@ -917,47 +915,6 @@ def test_has_one_with_touch_option_on_nonpersisted_built_associations_doesnt_upd
       car.build_special_bulb
     end
   end
-
-  class InvalidPost < Post
-    validate :always_fail
-
-    def always_fail
-      errors.add(:base, "Oops")
-    end
-  end
-
-  test "preserve old record if new one is invalid" do
-    author = Author.create!(id: 33, name: "Hank Moody")
-    author.create_post!(id: 1234, title: "Some title", body: "Some content")
-
-    assert_no_difference -> { Post.count } do
-      assert_raises ActiveRecord::RecordNotSaved do
-        author.post = InvalidPost.new(title: "Some title", body: "Some content")
-      end
-      author.save!
-    end
-  end
-
-  class SpecialContentPosition < ActiveRecord::Base
-    self.table_name = "content_positions"
-    belongs_to :content, class_name: name + "::SpecialContentPosition"
-    validates :content_id, presence: true, uniqueness: true
-  end
-
-  class SpecialContent < ActiveRecord::Base
-    self.table_name = "content"
-    has_one :content_position, dependent: :destroy, foreign_key: :content_id, class_name: SpecialContentPosition.name
-  end
-
-  test "uniqueness validator doesn't prevent from replacing the old record if dependent: :destroy is set" do
-    content = SpecialContent.create!
-    content.create_content_position!
-
-    assert_no_difference -> { ContentPosition.count } do
-      content.create_content_position!
-    end
-  end
-
   test "composite primary key malformed association class" do
     error = assert_raises(ActiveRecord::CompositePrimaryKeyMismatchError) do
       order = Cpk::BrokenOrder.new(id: [1, 2], book: Cpk::Book.new(title: "Some book"))