#28058: Empty Select widget (no choices) evaluates to False
--------------------------------+--------------------------------------
Reporter: László Károlyi | Owner: nobody
Type: Bug | Status: new
Component: Forms | Version: 1.11
Severity: Normal | Resolution:
Keywords: select widget | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 1
--------------------------------+--------------------------------------
Description changed by László Károlyi:
Old description:
> 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 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
New description:
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
--
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Ticket URL: <https://code.djangoproject.com/ticket/28058#comment:1>
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