Revert "Merge pull request #8017 from jcoglan/objectless_sessions"

This reverts commit 36376560fdd02f955ae3bf6b7792b784443660ad, reversing
changes made to 3148ed9a4bb7efef30b846dc945d73ceebcc3f0f.

Conflicts:
	actionpack/lib/action_dispatch/middleware/flash.rb

Reason: it broke Sam's CI

https://github.com/rails/rails/pull/8017#issuecomment-10210655

1 files changed, 9 insertions, 24 deletions

diff --git a/actionpack/lib/action_dispatch/middleware/flash.rb b/actionpack/lib/action_dispatch/middleware/flash.rb
index a162b791e5..9928b7cc3a 100644
--- a/actionpack/lib/action_dispatch/middleware/flash.rb
+++ b/actionpack/lib/action_dispatch/middleware/flash.rb
@@ -4,7 +4,7 @@ module ActionDispatch
     # read a notice you put there or <tt>flash["notice"] = "hello"</tt>
     # to put a new one.
     def flash
-      @env[Flash::KEY] ||= Flash::FlashHash.from_session_value(session["flash"])
+      @env[Flash::KEY] ||= (session["flash"] || Flash::FlashHash.new).tap(&:sweep)
     end
   end
 
@@ -70,31 +70,16 @@ module ActionDispatch
       end
     end
 
+    # Implementation detail: please do not change the signature of the
+    # FlashHash class. Doing that will likely affect all Rails apps in
+    # production as the FlashHash currently stored in their sessions will
+    # become invalid.
     class FlashHash
       include Enumerable
 
-      def self.from_session_value(value)
-        flash = case value
-                when FlashHash # Rails 3.1, 3.2
-                  new(value.instance_variable_get(:@flashes), value.instance_variable_get(:@used))
-                when Hash # Rails 4.0
-                  new(value['flashes'], value['discard'])
-                else
-                  new
-                end
-
-        flash.sweep
-        flash
-      end
-
-      def to_session_value
-        return nil if empty?
-        { 'discard' => @discard.to_a, 'flashes' => @flashes }
-      end
-
-      def initialize(flashes = {}, discard = []) #:nodoc:
-        @discard = Set.new(discard)
-        @flashes = flashes
+      def initialize #:nodoc:
+        @discard = Set.new
+        @flashes = {}
         @now     = nil
       end
 
@@ -238,7 +223,7 @@ module ActionDispatch
 
       if flash_hash
         if !flash_hash.empty? || session.key?('flash')
-          session["flash"] = flash_hash.to_session_value
+          session["flash"] = flash_hash
           new_hash = flash_hash.dup
         else
           new_hash = flash_hash