AttributeError raised by DatetimePicker

[huyuhuster]

ipywidgets/python/ipywidgets/ipywidgets/widgets/widget_datetime.py

Line 56 in 84abba0

if value.tzinfo is None:

This line will raise an error AttributeError when I clear the picked datetime. As described in:
vidartf/ipydatetime#8

venv/lib/python3.8/site-packages/ipydatetime/datetime_widget.py in _validate_tz(self, value)
    135 
    136     def _validate_tz(self, value):
--> 137         if value.tzinfo is not None:
    138             raise TraitError('%s values needs to be timezone unaware' % (self.__class__.__name__,))
    139         return value

AttributeError: 'NoneType' object has no attribute 'tzinfo'

[vidartf]

@huyuhuster The issue you linked describes a proposed solution. Do you have the opportunity to verify if that works? And if it does, would you be interested in making a PR with it? :)

[huyuhuster]

@huyuhuster The issue you linked describes a proposed solution. Do you have the opportunity to verify if that works? And if it does, would you be interested in making a PR with it? :)

@vidartf I will try that later. If it work, I will make a PR with it.

[vidartf]

@huyuhuster Actually, I'm not able to reproduce this, and we do have a unit test that covers this case:

ipywidgets/python/ipywidgets/ipywidgets/widgets/tests/test_widget_datetime.py

Lines 28 to 34 in 90e6be0

	def test_time_validate_value_none():
	t = datetime.datetime(2002, 2, 20, 13, 37, 42, 7, tzinfo=pytz.utc)
	t_min = datetime.datetime(1442, 1, 1, tzinfo=pytz.utc)
	t_max = datetime.datetime(2056, 1, 1, tzinfo=pytz.utc)
	w = DatetimePicker(value=t, min=t_min, max=t_max)
	w.value = None
	assert w.value is None

I've tested this with the version of Python indicated by the error report (py 3.8), and it doesn't seem to trigger for me. I've tried some older versions of traitlets as well, but I'm simply not able to reproduce it. Would you mind sharing which versions of python (CPython?), traitlets, and ipywidgets you are using?

[vidartf]

Ah, I see why the test didn't check it: the trait's _validate shortcuts for None if allow_none is true, but when being set from the client side with hold_traits_notification, this shortcut does not happen.