#28613: GenericForeignKey silently returns None when referring to non-existent
pk.
-------------------------------------+-------------------------------------
Reporter: Sjoerd | Owner: nobody
Job Postmus |
Type: | Status: new
Uncategorized |
Component: | Version: master
contrib.contenttypes |
Severity: Normal | Keywords: genericforeignkey
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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We have a model as follows.
{{{
class RemoteIdentifierToLocal(models.Model):
remote_id = models.UUIDField(primary_key=True)
local_object_content_type = models.ForeignKey(ContentType)
local_object_object_id = models.PositiveIntegerField()
local_object = GenericForeignKey(ct_field='local_object_content_type',
fk_field='local_object_object_id')
}}}
which is used as follows:
{{{
if guid is not None:
local_object =
RemoteIdentifierToLocal.objects.get(remote_id=guid).local_object
}}}
To my surprise, we found a case where `guid` was not-None, and
`local_object` was None.
This was traced back to the implementation of `GenericForeignKey`
containing a try/except-pass:
https://github.com/django/django/blob/master/django/contrib/contenttypes/fields.py#L241
(now)
https://github.com/django/django/commit/bca5327b21eb2e3ee18292cbe532d6d0071201d8
#diff-cc83843e623c1ab07a24317073330058R62 (initial commit, 11 years ago)
Now, apparently this has been this way for 11 years already, so must be
the "correct" behaviour. However I have not found any documentation of
this fact, and would (myself) expect the attribute-access to *do* raise an
exception or warning of some sort.
--
Ticket URL: <https://code.djangoproject.com/ticket/28613>
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