Empty Select widget (no choices) evaluates to False

[László Károlyi]

Hey guys,

I'm not sure I catched a bug, but I discovered a change between Django==1.10.6 and 1.11.

When you initialize a form with a Select widget, and the select widget has no choices (basically an empty tuple), when evaluating the field with bool(), it will evaluate to False. This causes the django_widget_tweaks module not to render a widget when trying to modify it from within a template, as it uses a bool-like evaluation to check if anything is passed to the set_attr.

code to reproduce:

from django import forms

class MyForm(forms.Form):
    select = forms.ChoiceField(choices=())

x = MyForm()

for item in x:
    print(bool(item))

It will print True with Django==1.10.6, and False with Django==1.11.

The underlying problem is that len() for a Boundfield with no choices will return 0 in the newer version, whereas it returns 1 in the older version.

the template code that fails to render with Django==1.11

{{ widget|set_attr('style:width: 100%') }}

Like I said, I'm not sure if this change is intended, nevertheless I reported it. Please let me know if this is intended, so I can let the creator of django_widget_tweaks know.

Cheers

[Tim Graham]

Bisected to b52c73008a9d67e9ddbb841872dc15cdd3d6ee01 (template-based widget rendering) though I haven't identified the cause of the change.

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In c09bf8d:

Fixed #28058 -- Restored empty BoundFields evaluating to True.

Regression in b52c73008a9d67e9ddbb841872dc15cdd3d6ee01

[Tim Graham <timograham@…>]

In 844ae40a:

[1.11.x] Fixed #28058 -- Restored empty BoundFields evaluating to True.

Regression in b52c73008a9d67e9ddbb841872dc15cdd3d6ee01

Backport of c09bf8d76770d39a4d9545b67598cd05adee281b from master