#19616: QuerySet.__contains__ tries to check the length of a None
-------------------------------------+-------------------------------------
Reporter: kalugny@… | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.4
(models, ORM) | Resolution:
Severity: Normal | Triage Stage:
Keywords: | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Old description:
> This is the code from QuerySet (version 1.42).
> As you can see by the lines I've bolded, although _result_cache might be
> None, it is still being checked for len()
>
> def __contains__(self, val):
> # The 'in' operator works without this method, due to __iter__.
> This
> # implementation exists only to shortcut the creation of Model
> # instances, by bailing out early if we find a matching element.
> pos = 0
> '''if self._result_cache is not None:'''
> if val in self._result_cache:
> return True
> elif self._iter is None:
> # iterator is exhausted, so we have our answer
> return False
> # remember not to check these again:
> pos = len(self._result_cache)
> '''else:'''
> # We need to start filling the result cache out. The
> following
> # ensures that self._iter is not None and self._result_cache
> is not
> # None
> it = iter(self)
>
> # Carry on, one result at a time.
> while True:
> ''' if len(self._result_cache) <= pos:'''
> self._fill_cache(num=1)
New description:
This is the code from QuerySet (version 1.42).
As you can see by the lines I've bolded, although _result_cache might be
None, it is still being checked for len()
{{{
def __contains__(self, val):
# The 'in' operator works without this method, due to __iter__.
This
# implementation exists only to shortcut the creation of Model
# instances, by bailing out early if we find a matching element.
pos = 0
if self._result_cache is not None:
if val in self._result_cache:
return True
elif self._iter is None:
# iterator is exhausted, so we have our answer
return False
# remember not to check these again:
pos = len(self._result_cache)
else:
# We need to start filling the result cache out. The following
# ensures that self._iter is not None and self._result_cache
is not
# None
it = iter(self)
# Carry on, one result at a time.
while True:
if len(self._result_cache) <= pos:
self._fill_cache(num=1)
}}}
--
Comment (by lukeplant):
Looking at the code and the comments in the `else` branch, it actually
seems very obvious that the function has covered it's bases about whether
self._result_cache is `None` or not. We need either some further analysis
as to why it is wrong, or a simple test case that ought to work.
--
Ticket URL: <https://code.djangoproject.com/ticket/19616#comment:3>
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