Use controller name as root when serializing an array and not root is defined

lib/action_controller/serialization.rb

@@ -71,6 +71,7 @@ module ActionController
       return unless serializer
 
       options[:scope] = serialization_scope unless options.has_key?(:scope)
+      options[:resource_name] = self.controller_name if resource.respond_to?(:to_ary)
 
       serializer.new(resource, options)
     end

lib/active_model/array_serializer.rb

@@ -16,6 +16,7 @@ module ActiveModel
       @object          = object
       @root            = options[:root]
       @root            = self.class._root if @root.nil?
+      @root            = options[:resource_name] if @root.nil?
       @meta_key        = options[:meta_key] || :meta
       @meta            = options[@meta_key]
       @each_serializer = options[:each_serializer]

test/integration/action_controller/serialization_test.rb

@@ -131,5 +131,21 @@ module ActionController
         assert_equal '{"hello":"world"}', @response.body
       end
     end
+
+    class ArraySerializerTest < ActionController::TestCase
+      class MyController < ActionController::Base
+        def render_array
+          render json: [Profile.new({ name: 'Name 1', description: 'Description 1', comments: 'Comments 1' })]
+        end
+      end
+
+      tests MyController
+
+      def test_render_array
+        get :render_array
+        assert_equal 'application/json', @response.content_type
+        assert_equal '{"my":[{"name":"Name 1","description":"Description 1"}]}', @response.body
+      end
+    end
   end
 end