From dc94c095031036ffc0f9ac0ee98a1162e57062eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Johan=20S=C3=B6rensen?= <johan@johansorensen.com>
Date: Thu, 28 May 2009 09:22:35 -0500
Subject: [PATCH] The FlashHash and friends causes a lot of needless session
 storing, when we know for a fact that there's no content in the flash. By not
 storing the empty hash in the session we save a lot of communication with the
 various session backends, while still keeping the same interface to the
 flash. [#2703 state:resolved]

Signed-off-by: Joshua Peek <josh@joshpeek.com>
---
 actionpack/lib/action_controller/flash.rb | 14 +++++++++++---
 actionpack/test/controller/flash_test.rb  |  7 ++++++-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/actionpack/lib/action_controller/flash.rb b/actionpack/lib/action_controller/flash.rb
index 56ee9c67e25f5..93912073ec795 100644
--- a/actionpack/lib/action_controller/flash.rb
+++ b/actionpack/lib/action_controller/flash.rb
@@ -120,6 +120,11 @@ def sweep #:nodoc:
         (@used.keys - keys).each{ |k| @used.delete(k) }
       end
 
+      def store(session, key = "flash")
+        return if self.empty?
+        session[key] = self
+      end
+
       private
         # Used internally by the <tt>keep</tt> and <tt>discard</tt> methods
         #     use()               # marks the entire flash as used
@@ -139,7 +144,10 @@ module InstanceMethods #:nodoc:
       protected
         def perform_action_with_flash
           perform_action_without_flash
-          remove_instance_variable(:@_flash) if defined? @_flash
+          if defined? @_flash
+            @_flash.store(session)
+            remove_instance_variable(:@_flash)
+          end
         end
 
         def reset_session_with_flash
@@ -151,8 +159,8 @@ def reset_session_with_flash
         # read a notice you put there or <tt>flash["notice"] = "hello"</tt>
         # to put a new one.
         def flash #:doc:
-          unless defined? @_flash
-            @_flash = session["flash"] ||= FlashHash.new
+          if !defined?(@_flash)
+            @_flash = session["flash"] || FlashHash.new
             @_flash.sweep
           end
 
diff --git a/actionpack/test/controller/flash_test.rb b/actionpack/test/controller/flash_test.rb
index d8a892811ef58..81c724a55d556 100644
--- a/actionpack/test/controller/flash_test.rb
+++ b/actionpack/test/controller/flash_test.rb
@@ -121,7 +121,7 @@ def test_update_flash
     assert_nil                  @response.template.assigns["flash_copy"]["that"], "On second flash"
     assert_equal "hello again", @response.template.assigns["flash_copy"]["this"], "On second flash"
   end
-  
+
   def test_flash_after_reset_session
     get :use_flash_after_reset_session
     assert_equal "hello",    @response.template.assigns["flashy_that"]
@@ -139,4 +139,9 @@ def test_sweep_after_halted_filter_chain
     get :std_action
     assert_nil @response.template.assigns["flash_copy"]["foo"]
   end
+
+  def test_does_not_set_the_session_if_the_flash_is_empty
+    get :std_action
+    assert_nil session["flash"]
+  end
 end