Specify type of singular association during serialization

When serialising a class, specify the type of any singular associations, if
necessary. Rails already correctly specifies the :type of any enumerable
association (e.g. a has_many association), but made no attempt to do so for
non-enumerables (e.g. a has_one association).
We must specify the :type of any STI association. A has_one
association to a class which uses single-table inheritance is an example of
this type of association.

Fixes #7471

1 files changed, 10 insertions, 2 deletions

diff --git a/activemodel/test/cases/serializers/xml_serialization_test.rb b/activemodel/test/cases/serializers/xml_serialization_test.rb
index 90ddf8ff0c..99a9c1fe33 100755
--- a/activemodel/test/cases/serializers/xml_serialization_test.rb
+++ b/activemodel/test/cases/serializers/xml_serialization_test.rb
@@ -6,12 +6,12 @@ require 'ostruct'
 class Contact
   include ActiveModel::Serializers::Xml
 
-  attr_accessor :address, :friends
+  attr_accessor :address, :friends, :contact
 
   remove_method :attributes if method_defined?(:attributes)
 
   def attributes
-    instance_values.except("address", "friends")
+    instance_values.except("address", "friends", "contact")
   end
 end
 
@@ -56,6 +56,9 @@ class XmlSerializationTest < ActiveModel::TestCase
     @contact.address.zip = 11111
     @contact.address.apt_number = 35
     @contact.friends = [Contact.new, Contact.new]
+    @related_contact = SerializableContact.new
+    @related_contact.name = "related"
+    @contact.contact = @related_contact
   end
 
   test "should serialize default root" do
@@ -256,4 +259,9 @@ class XmlSerializationTest < ActiveModel::TestCase
     assert_match %r{<address>}, xml
     assert_match %r{<apt-number type="integer">}, xml
   end
+
+  test "association with sti" do
+    xml = @contact.to_xml(include: :contact)
+    assert xml.include?(%(<contact type="SerializableContact">))
+  end
 end