AW: [Zope3-dev] Re: [ZODB-Dev] Problems with ZODB3-3.9.0_dev_r77011

[Gary Poster]

On Jul 19, 2007, at 10:36 AM, Roger Ineichen wrote:

> Hi Tobias
>
>> Auftrag von Gary Poster
>> Gesendet: Donnerstag, 19. Juli 2007 15:53
>> An: Tobias Rodäbel
>
> [...]
>
>>>
>>> zope.app.keyreference-3.5.0_dev_r77018-py2.4.egg requires
>>> ZODB3>=3.9.0-dev-r77011
>>>
>>> But there might be a caching problem within ZODB3-3.9.0 dev
>> r77011,
>>> my debug session tells:
>>>
>>>> /development/Zope3/MyProject/eggs/ZODB3-3.9.0_dev_r77011-py2.4-
>>> macosx-10.4-ppc.egg/ZODB/Connection.py(644)_store_objects()
>>> -> raise
>>> (Pdb) obj
>>> <zope.app.file.image.Image object at 0x3faadb0>
>>> (Pdb) oid
>>> '\x00\x00\x00\x00\x00\x00\x00\xc6'
>>> (Pdb) self._cache[oid]
>>> *** KeyError: '\x00\x00\x00\x00\x00\x00\x00\xc6'
>>> (Pdb) self._cache[oid] = obj
>>> *** TypeError: Cache values must be persistent objects.
>>>
>>> But zope.app.file.image.Image should be persistent.
>
> [...]
>
>>> Looking forward to some hints or help,
>>
>> Hi Tobias.  The ZODB 3.9 dev version is only different from 3.8 in
>> some conflict resolution code, for which I am responsible.  Some
>> thoughts.
>
> I'm pretty shure you ve got a LocationProxy arround your object
> because the zope.app.file doesn't implement ILocation.

Hey Roger.  I bet you are right.

...

> Gary
> -----
>
> This happens because of the call in
>
> ZODB.Connection.py
> $Id: Connection.py 75693 2007-05-11 22:18:37Z jim $
> cool that we have the revision info in the file header ;-)
> line: 627
>
> except:
>     # Dang, I bet it's wrapped:
>     # TODO:  Deprecate, then remove, this.
>     if hasattr(obj, 'aq_base'):
>         self._cache[oid] = obj.aq_base
>     else:
>         raise
>
> My question is, can we improve the method:
> if hasattr(obj, 'aq_base')
> and remove the proxy with a method that works?


I mentioned this to Jim.  If the masking of the original exception  
doesn't appear to lose any useful information, he'd prefer something  
like

if type(obj) is not obj.__class__:
     raise ValueError('object appears to be proxied', obj)
else:
     raise

IOW, don't guess, but give a more helpful error message

Gary