Allow default namespace inheritance

lib/action_controller/serialization.rb

@@ -85,8 +85,8 @@ module ActionController
         options[:scope] = serialization_scope unless options.has_key?(:scope)
 
         if resource.respond_to?(:to_ary)
-          options[:resource_name] = controller_name 
-          options[:namespace] = namespace_for_serializer if namespace_for_serializer
+          options[:resource_name] ||= controller_name 
+          options[:namespace] ||= namespace_for_serializer if namespace_for_serializer
         end
 
         serializer.new(resource, options)

lib/active_model/array_serializer.rb

@@ -35,7 +35,7 @@ module ActiveModel
 
     def serializer_for(item)
       serializer_class = @each_serializer || Serializer.serializer_for(item, namespace: @namespace) || DefaultSerializer
-      serializer_class.new(item, scope: scope, key_format: key_format, only: @only, except: @except, polymorphic: @polymorphic)
+      serializer_class.new(item, scope: scope, key_format: key_format, only: @only, except: @except, polymorphic: @polymorphic, namespace: @namespace)
     end
 
     def serializable_object

lib/active_model/serializer.rb

@@ -132,6 +132,7 @@ end
       @except        = options[:except] ? Array(options[:except]) : nil
       @key_format    = options[:key_format]
       @context       = options[:context]
+      @namespace     = options[:namespace]
     end
     attr_accessor :object, :scope, :root, :meta_key, :meta, :key_format, :context, :polymorphic
 
@@ -217,7 +218,8 @@ end
     end
 
     def association_options_for_serializer(association)
-      prefix = association.options[:prefix]
+      prefix    = association.options[:prefix]
+      namespace = association.options[:namespace] || @namespace || self.namespace
 
       { scope: scope }.tap do |opts|
         opts[:namespace] = namespace if namespace