django.utils.timezone functions raise AttributeError if DateTimeField allows null

[Daniel Swarbrick]

Since a null DateTimeField == None, and Python's None type does not contain a tzinfo attribute, the functions is_aware() and is_naive() will raise AttributeError.

[Aymeric Augustin]

By design, these functions expect to receive a datetime object and don't check the type of their argument. It's the caller's job to ensure that they aren't called with None, or a string, etc.

If I understand correctly, creating a model with a nullable DateTimeField and saving it without a value in the admin should trigger the problem?

[Daniel Swarbrick]

Correct. My model looks like this:

class Device(models.Model):
   ...
   last_poll = models.DateTimeField(blank=True, null=True)
   ...

When a Device object is created, it may have the value None in the last_poll field, to be populated at some later stage.

[Aymeric Augustin]

Thank for the clarification.

[Daniel Swarbrick]

Maybe instead of checking for a non-None value being passed, it might be more prudent to check isinstance(value, datetime) - or perhaps hasattr('tzinfo').

[Aymeric Augustin]

In [17148]:

Fixed #17294 -- Supported nullable DateTimeFields when time zone support is enabled. Thanks pressureman for the report.