Dump and load rack-cache stuff.

actionpack/lib/action_dispatch/http/rack_cache.rb

@@ -14,11 +14,15 @@ def initialize(store = RAILS_CACHE)
     end
 
     def read(key)
-      @store.read(key) || []
+      if data = @store.read(key)
+        Marshal.load(data)
+      else
+        []
+      end
     end
 
     def write(key, value)
-      @store.write(key, value)
+      @store.write(key, Marshal.dump(value))
     end
 
     ::Rack::Cache::MetaStore::RAILS = self

actionpack/test/dispatch/rack_cache_test.rb

+require 'abstract_unit'
+require 'action_dispatch/http/rack_cache'
+
+class RackCacheMetaStoreTest < ActiveSupport::TestCase
+  class ReadWriteHash < ::Hash
+    alias :read  :[]
+    alias :write :[]=
+  end
+
+  setup do
+    @store = ActionDispatch::RailsMetaStore.new(ReadWriteHash.new)
+  end
+
+  test "stuff is deep duped" do
+    @store.write(:foo, { :bar => :original })
+    hash = @store.read(:foo)
+    hash[:bar] = :changed
+    hash = @store.read(:foo)
+    assert_equal :original, hash[:bar]
+  end
+end