Merge lp:~mhall119/apps-brancher/fix-1010507 into lp:~dholbach/apps-brancher/trunk

[Michael Hall]

Use a copy of the app data, not the app data itself, before converting the timestamp to a serializable form

Well this was a fun one to track down, and has everything to do with how Python objects work.

When you use:
 data = app.__dict__
You aren't getting new dictionary with a copy of app's fields and data, it's actually the app itself in dictionary form.

So when you do:
 data['tarball_timestamp'] = 'foo'
You're actually changing app.tarball_timestamp as well.

Now, app was placed into the self.cache list. Not a copy of app, but a reference to the actual app instance. So, when you changed the dictionary form of the app instance, you also changed it in the cache.

So essentially, when saving the cache to a file, you were changing the in-memory cache so that the app instance it held had it's tarball_timestamp field converted from a datetime to an str.

Fun huh?

[Daniel Holbach (dholbach)]

WOW. Let me try this out.

=== modified file 'brancher/appcache.py'
--- brancher/appcache.py	2012-06-08 16:25:59 +0000
+++ brancher/appcache.py	2012-06-08 22:01:17 +0000
@@ -24,7 +24,7 @@
     def save(self):
         data = []
         for app in self.cache:
-            d = app.__dict__
+            d = dict(app.__dict__)
             if isinstance(d['tarball_timestamp'], datetime):
                 d['tarball_timestamp'] = app.tarball_timestamp.strftime("%Y-%m-%d %H:%M:%S")
             data += [ d ]