DateTimeField raises timezone awareness related RuntimeWarnings when it should'nt
|Reported by:||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
I've experienced some issues with wrong RuntimeWarnings about naive datetimes being raised when the
datetime I was using was perfectly timezone aware and I think I found the reason why:
In django/db/models/fields/init.py file, inside the definition of DateTimeField.to_python method,
the timezone awareness of a datetime is checked calling the isinstance function.
if isinstance(value, datetime.date): value = datetime.datetime(value.year, value.month, value.day) if settings.USE_TZ: # For backwards compatibility, interpret naive datetimes in # local time. This won't work during DST change, but we can't # do much about it, so we let the exceptions percolate up the # call stack. warnings.warn("DateTimeField %s.%s received a naive datetime " "(%s) while time zone support is active." % (self.model.__name__, self.name, value), RuntimeWarning)
Is true that, as said here https://docs.python.org/2.7/library/datetime.html#available-types,
"objects of the date type are always naive", but is wrong to use isinstance since all datetime.datetime
objects are also instances of datetime.date because datetime.datetime is a subclass of datetime.date
(which I think is confusing since breakes the OOP intuition that says that class inheritance should
describe "is a" relationships).
A posible solution is to compare using type(value) == datetime.date or, more clearly, check using django.utils.is_naive