[Zope3-dev] Weird error within __cmp__ method of KeyReferenceToPersistent

[Dominik Huber]

Hi,

Today I got a weird error caused by the __cmp__ method of 
KeyReferenceToPersistent. Unfortunately I couldn't setup a dedicated 
environment to reproduce the error within a test :(. The only evidence 
is this traceback:

Traceback (most recent call last):
  File "E:\workspace\bopp.ms\src\perse\generic\csv\base.py", line 208, 
in __call__
    importhandler(configuration)
[...]
  File "E:\workspace\bopp.ms\Zope3\src\zope\interface\adapter.py", line 
535, in subscribers
    subscription(*objects)
  File "E:\workspace\bopp.ms\Zope3\src\zope\app\intid\__init__.py", line 
165, in addIntIdSubscriber
    utility.register(key)
  File "E:\workspace\bopp.ms\Zope3\src\zope\app\intid\__init__.py", line 
112, in register
    if key in self.ids:
  File 
"E:\workspace\bopp.ms\Zope3\src\zope\app\keyreference\persistent.py", 
line 57, in __cmp__
    return cmp(
AttributeError: 'NoneType' object has no attribute 'db'

I would propose the following fix, but I'm not aware about all possible 
impacts. Therefore I'm asking for supervision.

class KeyReferenceToPersistent(object):
    [...]
    def _database_name(self):
        try:
            return self.object._p_jar.db().database_name
        except AttributeError:
            return ''

    def __cmp__(self, other):
        if self.key_type_id == other.key_type_id:
            return cmp(
                (self._database_name(),  self.object._p_oid),
                (other._database_name(), other.object._p_oid),
                )

        return cmp(self.key_type_id, other.key_type_id)

If there are no objections, I'm going to commit the fix tomorrow.

Regards,
Dominik

Internet www.perse.ch