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

test/adapter_test.rb

@@ -5,8 +5,8 @@ module ActiveModel
     class AdapterTest < Minitest::Test
       def setup
         profile = Profile.new
-        serializer = ProfileSerializer.new(profile)
-        @adapter = ActiveModel::Serializer::Adapter.new(serializer)
+        @serializer = ProfileSerializer.new(profile)
+        @adapter = ActiveModel::Serializer::Adapter.new(@serializer)
       end
 
       def test_serializable_hash_is_abstract_method
@@ -20,6 +20,10 @@ module ActiveModel
           @adapter.to_json(only: [:name])
         end
       end
+
+      def test_serializer
+        assert_equal @serializer, @adapter.serializer
+      end
     end
 
     class AdapterForTest < Minitest::Test