From 06c9e176ca1b74e99bc258295bfbd8d2f2f33563 Mon Sep 17 00:00:00 2001
From: Aaron Patterson <aaron.patterson@gmail.com>
Date: Sun, 29 Jul 2012 17:55:39 -0700
Subject: raise exceptions on header set after response committed

---
 actionpack/lib/action_controller/metal/live.rb | 21 +++++++++++++++++++++
 actionpack/lib/action_dispatch.rb              |  3 +++
 2 files changed, 24 insertions(+)

(limited to 'actionpack/lib')

diff --git a/actionpack/lib/action_controller/metal/live.rb b/actionpack/lib/action_controller/metal/live.rb
index aea00849d3..efeeefda9d 100644
--- a/actionpack/lib/action_controller/metal/live.rb
+++ b/actionpack/lib/action_controller/metal/live.rb
@@ -1,4 +1,5 @@
 require 'action_dispatch/http/response'
+require 'delegate'
 
 module ActionController
   module Live
@@ -30,6 +31,26 @@ module ActionController
         end
       end
 
+      class Header < DelegateClass(Hash)
+        def initialize(response, header)
+          @response = response
+          super(header)
+        end
+
+        def []=(k,v)
+          if @response.committed?
+            raise ActionDispatch::IllegalStateError, 'header already sent'
+          end
+
+          super
+        end
+      end
+
+      def initialize(status = 200, header = {}, body = [])
+        header = Header.new self, header
+        super(status, header, body)
+      end
+
       private
 
       def build_buffer(response, body)
diff --git a/actionpack/lib/action_dispatch.rb b/actionpack/lib/action_dispatch.rb
index 1e4ac70f3d..c259b865cc 100644
--- a/actionpack/lib/action_dispatch.rb
+++ b/actionpack/lib/action_dispatch.rb
@@ -36,6 +36,9 @@ end
 module ActionDispatch
   extend ActiveSupport::Autoload
 
+  class IllegalStateError < StandardError
+  end
+
   autoload_under 'http' do
     autoload :Request
     autoload :Response
-- 
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