Fix ValidationError on BooleanField with None value

fieldsignals/signals.py

@@ -4,7 +4,7 @@
 from typing import TYPE_CHECKING, Any
 
 from django.apps import apps
-from django.core.exceptions import AppRegistryNotReady
+from django.core.exceptions import AppRegistryNotReady, ValidationError
 from django.db.models import signals as _signals
 from django.db.models.fields.related import ForeignObjectRel
 from django.dispatch import Signal
@@ -169,7 +169,11 @@ def get_and_update_changed_fields(
             if field.attname in deferred_fields:
                 continue
             # using value_from_object instead of getattr() means we don't traverse foreignkeys
-            new_value = field.to_python(field.value_from_object(instance))
+            try:
+                new_value = field.to_python(field.value_from_object(instance))
+            except ValidationError:
+                # Skip fields with invalid values (e.g., BooleanField with None)
+                continue
             old_value = originals.get(field.name, None)
             if old_value != new_value:
                 if not isinstance(new_value, IMMUTABLE_TYPES_WHITELIST):

fieldsignals/tests/test_signals.py

@@ -8,7 +8,7 @@
 
 import pytest
 from django.apps import apps
-from django.core.exceptions import AppRegistryNotReady
+from django.core.exceptions import AppRegistryNotReady, ValidationError
 from django.db.models.fields.related import OneToOneRel
 from django.db.models.signals import post_init, post_save, pre_save
 from django.utils.dateparse import parse_datetime
@@ -69,6 +69,13 @@ def to_python(self, value: Any) -> datetime.datetime | None:
         return parse_datetime(value)
 
 
+class BooleanField(Field):
+    def to_python(self, value: Any) -> bool:
+        if value is None:
+            raise ValidationError('"None" value must be either True or False.')
+        return bool(value)
+
+
 class FakeModel:
     a_key = "a value"
     another = "something else"
@@ -104,6 +111,22 @@ def get_deferred_fields(self) -> set[str]:
         return {"b"}
 
 
+class BooleanFieldModel:
+    is_active: bool | None = None
+    name: str = "test"
+
+    class _meta:
+        @staticmethod
+        def get_fields() -> list[Field]:
+            return [
+                BooleanField("is_active"),
+                Field("name"),
+            ]
+
+    def get_deferred_fields(self) -> set[str]:
+        return set()
+
+
 class MockOneToOneRel(OneToOneRel):
     def __init__(self, name: str) -> None:
         self.name = name
@@ -169,6 +192,37 @@ def test_deferred_fields(self) -> None:
 
         assert list(obj._fieldsignals_originals.values()) == [{"a": 1}]
 
+    def test_boolean_field_with_none(self) -> None:
+        """
+        BooleanField.to_python(None) raises ValidationError.
+        Ensure post_init doesn't crash when field value is None.
+        """
+        with must_be_called(False) as test_func:
+            pre_save_changed.connect(test_func, sender=BooleanFieldModel)
+
+            obj = BooleanFieldModel()
+            # Should not raise ValidationError
+            post_init.send(instance=obj, sender=BooleanFieldModel)
+
+            # Only 'name' field should be tracked (is_active skipped due to ValidationError)
+            assert list(obj._fieldsignals_originals.values()) == [{"name": "test"}]
+
+    def test_boolean_field_transition_to_valid(self) -> None:
+        """
+        When a BooleanField transitions from invalid (None) to valid (True/False),
+        the signal should fire with old_value=None.
+        """
+        with must_be_called(True) as func:
+            pre_save_changed.connect(func, sender=BooleanFieldModel, fields=["is_active"])
+
+            obj = BooleanFieldModel()
+            post_init.send(instance=obj, sender=BooleanFieldModel)
+
+            obj.is_active = True
+            pre_save.send(instance=obj, sender=BooleanFieldModel)
+
+        assert func.kwargs["changed_fields"] == {"is_active": (None, True)}
+
 
 class TestPostSave:
     @pytest.fixture(autouse=True)