[1.7.x] Fixed #23795 -- Fixed a regression in custom form fields

Custom form fields having a `queryset` attribute but no
`limit_choices_to` could no longer be used in ModelForms.

Refs #2445.

Thanks to artscoop for the report.

Backport of bfb11b95 from master.

Conflicts:
	django/forms/fields.py

django/forms/fields.py

@@ -171,17 +171,6 @@ class Field(object):
         """
         return {}
 
-    def get_limit_choices_to(self):
-        """
-        Returns ``limit_choices_to`` for this form field.
-
-        If it is a callable, it will be invoked and the result will be
-        returned.
-        """
-        if callable(self.limit_choices_to):
-            return self.limit_choices_to()
-        return self.limit_choices_to
-
     def _has_changed(self, initial, data):
         """
         Return True if data differs from initial.

django/forms/models.py

@@ -329,11 +329,9 @@ class BaseModelForm(BaseForm):
         # Apply ``limit_choices_to`` to each field.
         for field_name in self.fields:
             formfield = self.fields[field_name]
-            if hasattr(formfield, 'queryset'):
-                limit_choices_to = formfield.limit_choices_to
+            if hasattr(formfield, 'queryset') and hasattr(formfield, 'get_limit_choices_to'):
+                limit_choices_to = formfield.get_limit_choices_to()
                 if limit_choices_to is not None:
-                    if callable(limit_choices_to):
-                        limit_choices_to = limit_choices_to()
                     formfield.queryset = formfield.queryset.complex_filter(limit_choices_to)
 
     def _get_validation_exclusions(self):
@@ -1118,6 +1116,17 @@ class ModelChoiceField(ChoiceField):
         self.choice_cache = None
         self.to_field_name = to_field_name
 
+    def get_limit_choices_to(self):
+        """
+        Returns ``limit_choices_to`` for this form field.
+
+        If it is a callable, it will be invoked and the result will be
+        returned.
+        """
+        if callable(self.limit_choices_to):
+            return self.limit_choices_to()
+        return self.limit_choices_to
+
     def __deepcopy__(self, memo):
         result = super(ChoiceField, self).__deepcopy__(memo)
         # Need to force a new ModelChoiceIterator to be created, bug #11183

docs/releases/1.7.2.txt

@@ -52,3 +52,7 @@ Bugfixes
 
 * Fixed a migration serializing bug involving ``float("nan")`` and
   ``float("inf")`` (:ticket:23770:).
+
+* Fixed a regression where custom form fields having a ``queryset`` attribute
+  but no ``limit_choices_to`` could not be used in a
+  :class:`~django.forms.ModelForm` (:ticket:`23795`).

tests/model_forms/tests.py

@@ -2345,6 +2345,17 @@ class StumpJokeForm(forms.ModelForm):
         fields = '__all__'
 
 
+class CustomFieldWithQuerysetButNoLimitChoicesTo(forms.Field):
+    queryset = 42
+
+
+class StumpJokeWithCustomFieldForm(forms.ModelForm):
+    custom = CustomFieldWithQuerysetButNoLimitChoicesTo()
+    class Meta:
+        model = StumpJoke
+        fields = ()  # We don't need any fields from the model
+
+
 class LimitChoicesToTest(TestCase):
     """
     Tests the functionality of ``limit_choices_to``.
@@ -2375,6 +2386,14 @@ class LimitChoicesToTest(TestCase):
         self.assertIn(self.threepwood, stumpjokeform.fields['has_fooled_today'].queryset)
         self.assertNotIn(self.marley, stumpjokeform.fields['has_fooled_today'].queryset)
 
+    def test_custom_field_with_queryset_but_no_limit_choices_to(self):
+        """
+        Regression test for #23795: Make sure a custom field with a `queryset`
+        attribute but no `limit_choices_to` still works.
+        """
+        f = StumpJokeWithCustomFieldForm()
+        self.assertEqual(f.fields['custom'].queryset, 42)
+
 
 class FormFieldCallbackTests(TestCase):