Chris McDonough wrote:
I think this problem is actually easier to solve in the common case than
requring that people run a conversion script.  The ZGlobals data
structure is a cache, and can be blown away and recreated
indiscriminately.  It's recreated whenever a Product is added or
removed, and Zope already does this as a matter of course if anything
about the data structure is goofy.

Hm, OK. Then the question is how to decide that it's goofy.

I'll note that I certainly did not intend it to be a cache when
I added it a long time ago.  I'm a bit uncomfortable assuming that
it's always used that way, but you know more than I about the current usage.

I think the problem Sidnei has run into isn't so much that the BTree
module can't be imported, it's instead that the
Persistence.PersistentMapping module redefines PersistentMapping in
order to do something I don't quite understand, and the redefinition is
what appears to be causing the AttributeError, 'data' to appear.

Hm, I'll add a comment explaining what's going on.

> If
it's not used, everything works fine. Here's the module:

 import Persistence
 import persistent
 from persistent.mapping import PersistentMapping

if Persistence.Persistent is not persistent.Persistent:
class PersistentMapping(Persistence.Persistent, PersistentMapping):
"""Legacy persistent mapping class
This class mixes in ExtensionClass Base if it is present.
Unless you actually want ExtensionClass semantics, use
persistent.mapping.PersistentMapping instead.

If you comment out the "if" clause and everything underneath of it, make
a dummy module with the following and put in in the software

from Globals import Persistent

 class BTree(Persistent):

... and restart Zope with an "old" filestorage file, all is well:

There needs to be a cleaner solution than this. A Dummy BTree module is not acceptable.


I'm not sure what the redefinition is supposed to achieve?

persistent.Persistent is not an extension class. It's a pure new-style persistent base class.

Persistent.Persistent is an extension class if ExtensionClass is
installed.  If ExtensionClass is not installed, then a warning is issued and
it is set tp persistent.Persistent.  This is to ease the transition for
people who use ZODB outside of Zope.

The check above is to cause an extension-class-based PersistentMapping
is ExtensionClass is installed.


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