id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
35126	forms.NullBooleanField's validation logic is surprising	Jeremy Lainé	nobody	"Reading NullBooleanField's code lead me to believe that it would clean `""1""` to `True`, and `""0""` to `False`"", just like `BooleanField` does:

https://github.com/django/django/blob/10c7c7320baf1c655fcb91202169d77725c9c4bd/django/forms/fields.py#L850

A simple field-level test works:

{{{
>>> from django import forms
>>> field = forms.NullBooleanField()
>>> field.clean(""1"")
True
>>> field.clean(""0"")
False
}}}

But using this in an actual form fails, note the difference between the `BooleanField` and `NullBooleanField`:

{{{
>>> class DemoForm(forms.Form):
...    field_a = forms.BooleanField()
...    field_b = forms.NullBooleanField()
...
>>> form = DemoForm({""field_a"": ""1"", ""field_b"": ""1""})
>>> form.is_valid()
>>> form.cleaned_data
{'field_a': True, 'field_b': None}
}}}

The problem is that by default `NullBooleanField` uses a `NullBooleanSelect` which mangles the submitted data for some obscure backwards-compatibility reason:

https://github.com/django/django/blob/10c7c7320baf1c655fcb91202169d77725c9c4bd/django/forms/widgets.py#L816

"	Bug	new	Forms	5.0	Normal				Unreviewed	0	0	0	0	0	0