Refactor and consolidate serializer option setup

lib/active_model/serializer/responder.rb

@@ -1,39 +1,16 @@
 module ActiveModel
   class Serializer
     class Responder < ::ActionController::Responder #:nodoc:
-      attr_reader :serializer
 
     protected
       def display(resource, given_options = {})
         if format != :json
           super
         else
-          default_options = controller.send(:default_serializer_options)
-          options = self.options.reverse_merge(default_options || {})
+          json = Serializer.build_json(controller, resource, options)
 
-          serializer = options[:serializer] ||
-            (resource.respond_to?(:active_model_serializer) &&
-             resource.active_model_serializer)
-
-          if resource.respond_to?(:to_ary)
-            unless serializer <= ActiveModel::ArraySerializer
-              raise ArgumentError.new("#{serializer.name} is not an ArraySerializer. " +
-                 "You may want to use the :each_serializer option instead.")
-            end
-
-            if options[:root] != false && serializer.root != false
-              # default root element for arrays is serializer's root or the controller name
-              # the serializer for an Array is ActiveModel::ArraySerializer
-              options[:root] ||= serializer.root || controller.send(:controller_name)
-            end
-          end
-
-          if serializer
-            serialization_scope = controller.send(:serialization_scope)
-            options[:scope] = serialization_scope unless options.has_key?(:scope)
-            options[:scope_name] = controller.send(:_serialization_scope)
-            options[:url_options] = controller.send(:url_options)
-            render(given_options.merge(self.options).merge(:json => serializer.new(resource, options)))
+          if json
+            render given_options.merge(options).merge(:json => json)
           else
             super
           end