Methods that return nil should not be considered YAML

3 files changed, 9 insertions, 0 deletions

diff --git a/activemodel/lib/active_model/serializers/xml.rb b/activemodel/lib/active_model/serializers/xml.rb
index d4295e6afe..19639b1363 100644
--- a/activemodel/lib/active_model/serializers/xml.rb
+++ b/activemodel/lib/active_model/serializers/xml.rb
@@ -33,6 +33,7 @@ module ActiveModel
         protected
 
           def compute_type
+            return if value.nil?
             type = ActiveSupport::XmlMini::TYPE_NAMES[value.class.name]
             type ||= :string if value.respond_to?(:to_str)
             type ||= :yaml
diff --git a/activemodel/test/cases/serializers/xml_serialization_test.rb b/activemodel/test/cases/serializers/xml_serialization_test.rb
index b6a2f88667..8f5c196850 100644
--- a/activemodel/test/cases/serializers/xml_serialization_test.rb
+++ b/activemodel/test/cases/serializers/xml_serialization_test.rb
@@ -92,6 +92,10 @@ class XmlSerializationTest < ActiveModel::TestCase
   test "should serialize string" do
     assert_match %r{<name>aaron stack</name>}, @contact.to_xml
   end
+  
+  test "should serialize nil" do
+    assert_match %r{<pseudonyms nil=\"true\"></pseudonyms>}, @contact.to_xml(:methods => :pseudonyms)
+  end
 
   test "should serialize integer" do
     assert_match %r{<age type="integer">25</age>}, @contact.to_xml
diff --git a/activemodel/test/models/contact.rb b/activemodel/test/models/contact.rb
index f4f3078473..7bfc542afb 100644
--- a/activemodel/test/models/contact.rb
+++ b/activemodel/test/models/contact.rb
@@ -16,6 +16,10 @@ class Contact
     options.each { |name, value| send("#{name}=", value) }
   end
 
+  def pseudonyms
+    nil
+  end
+
   def persisted?
     id
   end