[kupfer] puid: Check "class version number" in SerializedObject

[Ulrik Sverdrup <usverdrup src gnome org>]

commit a281daaacdc77b276978386e3d1904ea8410f05d
Author: Ulrik Sverdrup <ulrik sverdrup gmail com>
Date:   Sat Jan 9 15:32:01 2010 +0100

    puid: Check "class version number" in SerializedObject

 kupfer/puid.py |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/kupfer/puid.py b/kupfer/puid.py
index 897d746..a6b32b8 100644
--- a/kupfer/puid.py
+++ b/kupfer/puid.py
@@ -17,12 +17,18 @@ from kupfer import pretty
 SERIALIZABLE_ATTRIBUTE = "serilizable"
 
 class SerializedObject (object):
+	# treat the serilizable attribute as a version number, defined on the class
 	def __init__(self, obj):
 		self.data = pickle.dumps(obj, pickle.HIGHEST_PROTOCOL)
+		self.version = getattr(obj, SERIALIZABLE_ATTRIBUTE)
 	def __eq__(self, other):
-		return isinstance(other, type(self)) and self.data == other.data
+		return (isinstance(other, type(self)) and self.data == other.data and
+		        self.version == other.version)
 	def reconstruct(self):
-		return pickle.loads(self.data)
+		obj = pickle.loads(self.data)
+		if self.version != getattr(obj, SERIALIZABLE_ATTRIBUTE):
+			raise ValueError("Version mismatch for reconstructed %s" % obj)
+		return obj
 
 def get_unique_id(obj):
 	if obj is None: