Add NullAdapater

lib/active_model/serializer/adapter.rb

@@ -3,6 +3,7 @@ module ActiveModel
     class Adapter
       extend ActiveSupport::Autoload
       autoload :SimpleAdapter
+      autoload :NullAdapter
 
       def initialize(serializer)
         @attributes = serializer.attributes

lib/active_model/serializer/adapter/null_adapter.rb

@@ -0,0 +1,15 @@
+module ActiveModel
+  class Serializer
+    class Adapter
+      class NullAdapter < Adapter
+        def serializable_hash(options = {})
+          {}
+        end
+
+        def to_json(options = {})
+          serializable_hash.to_json
+        end
+      end
+    end
+  end
+end