Serializer should be available wiithing adapter to inspect attributes and assotions

lib/active_model/serializer/adapter.rb

@@ -5,8 +5,10 @@ module ActiveModel
       autoload :SimpleAdapter
       autoload :NullAdapter
 
+      attr_reader :serializer
+
       def initialize(serializer)
-        @attributes = serializer.attributes
+        @serializer = serializer
       end
 
       def serializable_hash(options = {})

lib/active_model/serializer/adapter/simple_adapter.rb

@@ -3,7 +3,7 @@ module ActiveModel
     class Adapter
       class SimpleAdapter < Adapter
         def to_json(options={})
-          @attributes.each_with_object({}) do |(attr, value), h|
+          serializer.attributes.each_with_object({}) do |(attr, value), h|
             h[attr] = value
           end.to_json # FIXME: why does passing options here cause {}?
         end