ModelSelect2Widget broken for empty fields in 7.6.0

[mikemanger]

Describe the bug
I have a widget that lets me search models related to another model. It worked as expected in 7.5.0, but is causing a 500 error in 7.6.0 when expanding the select2 (searching with an empty string should just show the first x results I think). I think it is because a check for empty strings was removed in #26.

Exception & Traceback

Internal Server Error: /premises/select2_flock_lookup/auto.json
Traceback (most recent call last):
  File "C:\Path\env\lib\site-packages\django\db\models\fields\__init__.py", line 1774, in get_prep_value
    return int(value)
ValueError: invalid literal for int() with base 10: ''

The above exception was the direct cause of the following exception:

Traceback (most recent call last):

  File "C:\Path\env\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "C:\Path\env\lib\site-packages\django\core\handlers\base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Path\env\lib\site-packages\django\views\generic\base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "C:\Path\env\lib\site-packages\django\views\generic\base.py", line 98, in dispatch
    return handler(request, *args, **kwargs)
  File "C:\Path\env\lib\site-packages\django_select2\views.py", line 37, in get
    self.object_list = self.get_queryset()
  File "C:\Path\premises\views.py", line 153, in get_queryset
    cached_queryset = super().get_queryset()
  File "C:\Path\env\lib\site-packages\django_select2\views.py", line 57, in get_queryset
    return self.widget.filter_queryset(
  File "C:\Path\env\lib\site-packages\django_select2\forms.py", line 414, in filter_queryset
    return queryset.filter(select).distinct()
  File "C:\Path\env\lib\site-packages\django\db\models\query.py", line 942, in filter
    return self._filter_or_exclude(False, *args, **kwargs)
  File "C:\Path\env\lib\site-packages\django\db\models\query.py", line 962, in _filter_or_exclude
    clone._filter_or_exclude_inplace(negate, *args, **kwargs)
  File "C:\Path\env\lib\site-packages\django\db\models\query.py", line 969, in _filter_or_exclude_inplace
    self._query.add_q(Q(*args, **kwargs))
  File "C:\Path\env\lib\site-packages\django\db\models\sql\query.py", line 1358, in add_q
    clause, _ = self._add_q(q_object, self.used_aliases)
  File "C:\Path\env\lib\site-packages\django\db\models\sql\query.py", line 1377, in _add_q
    child_clause, needed_inner = self.build_filter(
  File "C:\Path\env\lib\site-packages\django\db\models\sql\query.py", line 1237, in build_filter
    return self._add_q(
  File "C:\Path\env\lib\site-packages\django\db\models\sql\query.py", line 1377, in _add_q
    child_clause, needed_inner = self.build_filter(
  File "C:\Path\env\lib\site-packages\django\db\models\sql\query.py", line 1319, in build_filter
    condition = self.build_lookup(lookups, col, value)
  File "C:\Path\env\lib\site-packages\django\db\models\sql\query.py", line 1165, in build_lookup
    lookup = lookup_class(lhs, rhs)
  File "C:\Path\env\lib\site-packages\django\db\models\lookups.py", line 24, in __init__
    self.rhs = self.get_prep_lookup()
  File "C:\Path\env\lib\site-packages\django\db\models\lookups.py", line 76, in get_prep_lookup
    return self.lhs.output_field.get_prep_value(self.rhs)
  File "C:\Path\env\lib\site-packages\django\db\models\fields\__init__.py", line 1776, in get_prep_value
    raise e.__class__(
ValueError: Field 'house_number' expected a number but got ''.

Code Snippet

# widgets.py
class HouseSelectWidget(ModelSelect2Widget):
    """Used in forms to search for houses"""
    model = House
    search_fields = [
        'house_number',
    ]

    def __init__(self, attrs=None, choices=(), **kwargs):
        if 'data_view' not in kwargs:
            kwargs['data_view'] = 'premises:select2_house_lookup'
        super().__init__(attrs=None, choices=(), **kwargs)

    def build_attrs(self, base_attrs, extra_attrs=None):
        self.attrs.setdefault('data-minimum-input-length', 0)
        return super().build_attrs(base_attrs, extra_attrs)

# views.py
class HouseAutoResponseView(AutoResponseView):
    """
    Used by select2 for filtering by subscriber.
    """
    def get_queryset(self):
        cached_queryset = super().get_queryset()
        # code that filters the queryset by current user
        return cached_queryset

To Reproduce
This is using Django 3.1.5 with Python 3.8.7 on Windows and also tested on Linux with the same config.

[codingjoe]

Good catch, yes, we should filter on an empty search term. I'll create a patch.

[codingjoe]

Patch was released in 7.6.1 🎉

Thanks again @mikemanger