datetimes method always raise AttributeError

[Enrique Martínez <enrique@…>]

NewsItem.objects.all().datetimes('date_time', 'month', order='DESC') always raises: AttributeError: 'DateTimeQuery' object has no attribute 'tzinfo'

and it happens with all my models with some DateTimeField.

[Tim Graham]

I can reproduce this on the tutorial with the following query: Poll.objects.datetimes('pub_date', 'month') (Python 2.7, pytz 2013.8, settings.USE_TZ=True). Tentatively marking as a release blocker as I don't see anything wrong with that based on the documentation. On the other hand, we have tests that seem to test the same thing, so wihout digging in I'm unsure what the issue might be.

[Tim Graham]

>>> Poll.objects.datetimes('pub_date', 'month')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/home/timgraham/code/django/django/db/models/query.py", line 115, in __repr__
    data = list(self[:REPR_OUTPUT_SIZE + 1])
  File "/home/timgraham/code/django/django/db/models/query.py", line 140, in __iter__
    self._fetch_all()
  File "/home/timgraham/code/django/django/db/models/query.py", line 962, in _fetch_all
    self._result_cache = list(self.iterator())
  File "/home/timgraham/code/django/django/db/models/sql/compiler.py", line 1089, in results_iter
    datetime = timezone.make_aware(datetime, self.query.tzinfo)
AttributeError: 'DateTimeQuery' object has no attribute 'tzinfo'

[Baptiste Mispelon]

Bisecting the error lead me to commit 70679243d1786e03557c28929f9762a119e3ac14, but it's not really obvious (to me anyway) why that would have broken the feature.

[Anssi Kääriäinen]

It is possible the above commit just makes the error loud instead of hiding the error and returning silently []. Before the commit errors inside queryset iteration led to empty list as result.

[Baptiste Mispelon]

Replying to akaariai:

It is possible the above commit just makes the error loud instead of hiding the error and returning silently []. Before the commit errors inside queryset iteration led to empty list as result.

Indeed, this appears to be the case.

While digging, I also found out that the following code works:

qs = Poll.objects.datetimes('pub_date', 'month')
list(qs)
repr(qs)

While this one doesn't (note how repr and list have been switched):

qs = Poll.objects.datetimes('pub_date', 'month')
repr(qs)
list(qs)

This explains why this issue has been able to fall through the cracks: iterating over a queryset is a much more common use-case than displaying it as-is.

Unfortunately, I haven't been able to identify exactly where the problem lies (I have a suspicion that it's got something to do with the _clone method though) but I've managed to come up with a failing testcase (see attached).

[Baptiste Mispelon]

Failing testcase

[Anssi Kääriäinen]

Yeah, the problem seem to be that when doing qs.datetimes() the DateTimeQuery gets a tzinfo attribute (datetimes() end up in here: ​https://github.com/django/django/blob/master/django/db/models/query.py#L1255), but if the query gets cloned afterwards the tzinfo attribute will not get cloned. The solution seems to be to write a custom .clone() for DateTimeQuery.

[loic84]

PR ​https://github.com/django/django/pull/1919.

[Aymeric Augustin]

The patch looks appropriate.

The test could be simplified a bit with now = timezone.now().replace(microsecond=0).

[Baptiste Mispelon]

Patch looks good.

It fixes the issue and the full test suite still passes after applying it.

[Baptiste Mispelon <bmispelon@…>]

In 17ed99f3a3eea4bd27fa34be59c3582616ed8079:

Fixed #21432 -- DateTimeQuery now copies tzinfo when cloning.

Thanks Enrique Martínez for the report and @bmispelon for the tests.

[Baptiste Mispelon <bmispelon@…>]

In 67c30426c1370f5d6c39bd73888c3902c1c5f365:

[1.6.x] Fixed #21432 -- DateTimeQuery now copies tzinfo when cloning.

Thanks Enrique Martínez for the report and @bmispelon for the tests.

Backport of 17ed99f3a3eea4bd27fa34be59c3582616ed8079 from master.

[Loic Bistuer <loic.bistuer@…>]

In 32e75803be8b3e9c35e6735c265125c4130ffabc:

Fixed typo and slightly improved error message when db is missing time zone definitions.

Refs #21432.

[Tim Graham <timograham@…>]

In 3bb7de8c7c3f9d5de5426d94f45fe83b5d998357:

[1.6.x] Fixed typo and slightly improved error message when db is missing time zone definitions.

Refs #21432.

Backport of 32e75803be from master