Simplify attribute and callback calculation by extracting order of processing to separate method

lib/factory_girl/attribute_list.rb

@@ -19,9 +19,7 @@ module FactoryGirl
     end
 
     def apply_attributes(attributes_to_apply)
-      attributes_to_apply.each do |attribute|
-        add_attribute(attribute) unless attribute_defined?(attribute.name)
-      end
+      attributes_to_apply.each {|attribute| add_attribute(attribute) }
     end
 
     private

lib/factory_girl/factory.rb

@@ -95,27 +95,27 @@ module FactoryGirl
 
     def class_name #:nodoc:
       @class_name || parent.class_name || name
-
     end
 
     def attributes
       compile
       AttributeList.new(@name).tap do |list|
-        traits.each do |trait|
-          list.apply_attributes(trait.attributes)
+        processing_order.each do |factory|
+          list.apply_attributes factory.attributes
         end
-
-        list.apply_attributes(@definition.attributes)
-        list.apply_attributes(parent.attributes)
       end
     end
 
     def callbacks
-      [parent.callbacks, traits.map(&:callbacks).reverse, @definition.callbacks].flatten
+      processing_order.map {|factory| factory.callbacks }.flatten
     end
 
     private
 
+    def processing_order
+      [parent, traits.reverse, @definition].flatten
+    end
+
     def assert_valid_options(options)
       options.assert_valid_keys(:class, :parent, :default_strategy, :aliases, :traits)