#18416 closed Bug (wontfix)
Query fails when SimpleLazyObject evaluates to None
Reported by: | Bouke Haarsma | Owned by: | nobody |
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Component: | Database layer (models, ORM) | Version: | 1.4 |
Severity: | Normal | Keywords: | |
Cc: | dougvanhorn | Triage Stage: | Unreviewed |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
Relevant excerpt from model definition:
class Event(models.Model): season = models.ForeignKey(Season)
Expected result:
>>> Event.objects.filter(season=None) []
Actual result:
>>> from django.utils.functional import SimpleLazyObject >>> lazy = SimpleLazyObject(lambda: None) >>> lazy <django.utils.functional.SimpleLazyObject object at 0x10203cd90> >>> print lazy None >>> Event.objects.filter(season=lazy) Traceback (most recent call last): File "<console>", line 1, in <module> File "django/db/models/manager.py", line 143, in filter return self.get_query_set().filter(*args, **kwargs) File "django/db/models/query.py", line 621, in filter return self._filter_or_exclude(False, *args, **kwargs) File "django/db/models/query.py", line 639, in _filter_or_exclude clone.query.add_q(Q(*args, **kwargs)) File "django/db/models/sql/query.py", line 1250, in add_q can_reuse=used_aliases, force_having=force_having) File "django/db/models/sql/query.py", line 1185, in add_filter connector) File "django/db/models/sql/where.py", line 69, in add value = obj.prepare(lookup_type, value) File "django/db/models/sql/where.py", line 320, in prepare return self.field.get_prep_lookup(lookup_type, value) File "django/db/models/fields/related.py", line 137, in get_prep_lookup return self._pk_trace(value, 'get_prep_lookup', lookup_type) File "django/db/models/fields/related.py", line 210, in _pk_trace v = getattr(field, prep_func)(lookup_type, v, **kwargs) File "django/db/models/fields/__init__.py", line 310, in get_prep_lookup return self.get_prep_value(value) File "django/db/models/fields/__init__.py", line 537, in get_prep_value return int(value) TypeError: int() argument must be a string or a number, not 'SimpleLazyObject'
The SimpleLazyObject
initialization is somewhat more complicated then depicted above, but it can evaluate to None
. However, if it evaluates to None
, it cannot be used as-is in the query and results in the exception as listed above.
Change History (7)
comment:1 by , 12 years ago
Resolution: | → wontfix |
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Status: | new → closed |
comment:2 by , 12 years ago
And yet, when you accidentally pass None, django gives you that really tall call stack with an unrelated error message at the bottom. Couldn't a better message be issued?
comment:3 by , 12 years ago
I just bumped into this bug. I'm not going to muck with the status, but I wanted to document my thoughts in case anyone else wants to take up the cause on this (I've found it to be a tedious, political process).
The code that raises the exception is this (it's found in most of the Field types):
def get_prep_value(self, value): if value is None: return None return int(value)
It's the value is None
that causes the problem. It's an identity test.
If the intent of the if-test is to return None
when the supplied value equates to None
, then the if-test should be re-written as value == None
, which would test for equality. The equality test is slower, though, so you'll likely find argument against using it in this section of the code. Oddly built objects with __eq__
overloaded might also find trouble.
So there may not be much to do here, leaving the burden on the user to figure out what's going on. But I wanted to add some documentation to this bug for future reference.
For what it's worth, I ran into this problem with the following code:
try: agreement = Agreement.objects.get(user=request.user) except Agreement.DoesNotExist, e: agreement = Agreement(user=request.user)
I ended up wrapping the view in the login_required
decorator, which makes the .user
evaluate to something, preventing the bug. But as stated by bouke, the stack is not very helpful.
comment:4 by , 12 years ago
Cc: | added |
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comment:5 by , 12 years ago
Same thing happened to me just now. I believe a common case is request.user
in unit tests. Maybe request.user
shouldn't be a SimpleLazyObject
after all.
comment:6 by , 9 years ago
Also have this issue now. Now with request.user, but with another object (some model instance) I wanted to be evaluated lazyly.
I'm curious how you fixed it? Completely new LazyObject Class, or is there some quick hack?
I guess I will do a quick test for None before I create the lazyobject. I guess it takes another database call, but I don't know how to do it otherwise.
comment:7 by , 7 years ago
I also am curious if anyone came up with a good solution for this. I use my own custom user object, and also a organization object that are both attached to the request in middlewares as SimpleLazyObjects
that have a None
value if they are not logged in or if the logged in user is not part of an organization. Currently attaching to models is a real pain
Action.objects.create( organization=request.organization if request.organization else None, ... )
And what is really bad is that if you forget this and don't test with a user without an organization it can easily go unnoticed!
WONTFIX, I'm afraid. There is nothing we could do apart from putting a special case for
SimpleLazyObject
inget_prep_value()
where theis None
test gets done, which would be horrible.It is Simple Lazy Object after all.