Clear the context per request, and assign a controller reference that is used to create a new view context on demand if needed by draper outside of a template context. Fixes #287. Split out the system initialization into action_controller and action_mailer pieces for clarity. Guarded the view context lazy initialization to only attempt to create a test context if the proper test classes exist (as they won't outside of test mode).

lib/draper/railtie.rb

@@ -24,13 +24,13 @@ module Draper
 
     initializer "draper.extend_action_controller_base" do |app|
       ActiveSupport.on_load(:action_controller) do
-        Draper::System.setup(self)
+        Draper::System.setup_action_controller(self)
       end
     end
 
     initializer "draper.extend_action_mailer_base" do |app|
       ActiveSupport.on_load(:action_mailer) do
-        Draper::System.setup(self)
+        Draper::System.setup_action_mailer(self)
       end
     end
 

lib/draper/system.rb

@@ -1,10 +1,18 @@
 module Draper
   class System
-    def self.setup(component)
+    def self.setup_action_controller(component)
       component.class_eval do
         include Draper::ViewContext
-        extend  Draper::HelperSupport unless defined?(::ActionMailer) && self.is_a?(::ActionMailer::Base)
+        extend  Draper::HelperSupport
+        before_filter lambda {|controller|
+          Draper::ViewContext.current = nil
+          Draper::ViewContext.current_controller = controller
+        }
       end
     end
+
+    def self.setup_action_mailer(component)
+      include Draper::ViewContext
+    end
   end
 end

lib/draper/view_context.rb

@@ -1,11 +1,19 @@
 module Draper
   module ViewContext
+    def self.current_controller
+      Thread.current[:current_controller] || ApplicationController.new
+    end
+
+    def self.current_controller=(controller)
+      Thread.current[:current_controller] = controller
+    end
+
     def self.current
       Thread.current[:current_view_context] ||= build_view_context
     end
 
-    def self.current=(input)
-      Thread.current[:current_view_context] = input
+    def self.current=(context)
+      Thread.current[:current_view_context] = context
     end
 
     def view_context
@@ -17,10 +25,12 @@ module Draper
     private
 
     def self.build_view_context
-      ApplicationController.new.view_context.tap do |context|
-        context.controller.request ||= ActionController::TestRequest.new
-        context.request            ||= context.controller.request
-        context.params             ||= {}
+      current_controller.view_context.tap do |context|
+        if defined?(ActionController::TestRequest)
+          context.controller.request ||= ActionController::TestRequest.new
+          context.request            ||= context.controller.request
+          context.params             ||= {}
+        end
       end
     end
   end

spec/spec_helper.rb

@@ -32,7 +32,7 @@ require 'action_controller/test_case'
 
 module ActionController
   class Base
-    Draper::System.setup(self)
+    Draper::System.setup_action_controller(self)
   end
 end