2 files changed, 28 insertions, 14 deletions
diff --git a/actionpack/lib/abstract_controller/collector.rb b/actionpack/lib/abstract_controller/collector.rb
index 09b9e7ddf0..ddd56b354a 100644
--- a/actionpack/lib/abstract_controller/collector.rb
+++ b/actionpack/lib/abstract_controller/collector.rb
@@ -23,7 +23,17 @@ module AbstractController
   protected
 
     def method_missing(symbol, &block)
-      mime_constant = Mime.const_get(symbol.upcase)
+      const_name = symbol.upcase
+
+      unless Mime.const_defined?(const_name)
+        raise NoMethodError, "To respond to a custom format, register it as a MIME type first: " \
+          "http://guides.rubyonrails.org/action_controller_overview.html#restful-downloads. " \
+          "If you meant to respond to a variant like :tablet or :phone, not a custom format, " \
+          "be sure to nest your variant response within a format response: " \
+          "format.html { |html| html.tablet { ... } }"
+      end
+
+      mime_constant = Mime.const_get(const_name)
 
       if Mime::SET.include?(mime_constant)
         AbstractController::Collector.generate_method_for_mime(mime_constant)
diff --git a/actionpack/lib/abstract_controller/rendering.rb b/actionpack/lib/abstract_controller/rendering.rb
index 6f6079d3c5..ce3a0316c4 100644
--- a/actionpack/lib/abstract_controller/rendering.rb
+++ b/actionpack/lib/abstract_controller/rendering.rb
@@ -1,5 +1,6 @@
 require 'active_support/concern'
 require 'active_support/core_ext/class/attribute'
+require 'set'
 
 module AbstractController
   class DoubleRenderError < Error
@@ -13,11 +14,6 @@ module AbstractController
   module Rendering
     extend ActiveSupport::Concern
 
-    included do
-      class_attribute :protected_instance_variables
-      self.protected_instance_variables = []
-    end
-
     # Normalize arguments, options and then delegates render_to_body and
     # sticks the result in self.response_body.
     # :api: public
@@ -55,21 +51,23 @@ module AbstractController
       Mime::TEXT
     end
 
-    DEFAULT_PROTECTED_INSTANCE_VARIABLES = %w(
+    DEFAULT_PROTECTED_INSTANCE_VARIABLES = Set.new %w(
       @_action_name @_response_body @_formats @_prefixes @_config
       @_view_context_class @_view_renderer @_lookup_context
-    )
+      @_routes @_db_runtime
+    ).map(&:to_sym)
 
     # This method should return a hash with assigns.
     # You can overwrite this configuration per controller.
     # :api: public
     def view_assigns
-      hash = {}
-      variables  = instance_variables
-      variables -= protected_instance_variables
-      variables -= DEFAULT_PROTECTED_INSTANCE_VARIABLES
-      variables.each { |name| hash[name[1..-1]] = instance_variable_get(name) }
-      hash
+      protected_vars = _protected_ivars
+      variables      = instance_variables
+
+      variables.reject! { |s| protected_vars.include? s }
+      variables.each_with_object({}) { |name, hash|
+        hash[name.slice(1, name.length)] = instance_variable_get(name)
+      }
     end
 
     # Normalize args by converting render "foo" to render :action => "foo" and
@@ -104,8 +102,14 @@ module AbstractController
     # :api: private
     def _normalize_render(*args, &block)
       options = _normalize_args(*args, &block)
+      #TODO: remove defined? when we restore AP <=> AV dependency
+      options[:variant] = request.variant if defined?(request) && request.variant.present?
       _normalize_options(options)
       options
     end
+
+    def _protected_ivars # :nodoc:
+      DEFAULT_PROTECTED_INSTANCE_VARIABLES
+    end
   end
 end