Add type validation for foreign key and one to one model consistency

CHANGELOG.rst

@@ -14,6 +14,7 @@ Changelog
 Added
 ^^^^^
 - Implement savepoints for transactions (#1816)
+- Added type validation for foreign key fields to ensure type safety. Now raises `ValidationError` when assigning foreign key values with incorrect model types (#1792)
 
 Fixed
 ^^^^^
@@ -1497,4 +1498,4 @@ Docs/examples:
 
       await Tournament.filter(
           events__name__in=['1', '3']
-      ).order_by('-events__participants__name').distinct()
+      ).order_by('-events__participants__name').distinct()

tests/fields/test_fk.py

@@ -1,10 +1,20 @@
 from tests import testmodels
 from tortoise.contrib import test
-from tortoise.exceptions import IntegrityError, NoValuesFetched, OperationalError
+from tortoise.exceptions import (
+    IntegrityError,
+    NoValuesFetched,
+    OperationalError,
+    ValidationError,
+)
 from tortoise.queryset import QuerySet
 
 
 class TestForeignKeyField(test.TestCase):
+    def assertRaisesWrongTypeException(self, relation_name: str):
+        return self.assertRaisesRegex(
+            ValidationError, f"Invalid type for relationship field '{relation_name}'"
+        )
+
     async def test_empty(self):
         with self.assertRaises(IntegrityError):
             await testmodels.MinRelation.create()
@@ -151,6 +161,11 @@ async def test_minimal__instantiated_create(self):
         tour = await testmodels.Tournament.create(name="Team1")
         await testmodels.MinRelation.create(tournament=tour)
 
+    async def test_minimal__instantiated_create_wrong_type(self):
+        author = await testmodels.Author.create(name="Author1")
+        with self.assertRaisesWrongTypeException("tournament"):
+            await testmodels.MinRelation.create(tournament=author)
+
     async def test_minimal__instantiated_iterate(self):
         tour = await testmodels.Tournament.create(name="Team1")
         async for _ in tour.minrelations:
@@ -229,3 +244,57 @@ async def test_event__offset(self):
         event2 = await testmodels.Event.create(name="Event2", tournament=tour)
         event3 = await testmodels.Event.create(name="Event3", tournament=tour)
         self.assertEqual(await tour.events.offset(1).order_by("name"), [event2, event3])
+
+    async def test_fk_correct_type_assignment(self):
+        tour1 = await testmodels.Tournament.create(name="Team1")
+        tour2 = await testmodels.Tournament.create(name="Team2")
+        event = await testmodels.Event(name="Event1", tournament=tour1)
+
+        event.tournament = tour2
+        await event.save()
+        self.assertEqual(event.tournament_id, tour2.id)
+
+    async def test_fk_wrong_type_assignment(self):
+        tour = await testmodels.Tournament.create(name="Team1")
+        author = await testmodels.Author.create(name="Author")
+        rel = await testmodels.MinRelation.create(tournament=tour)
+
+        with self.assertRaisesWrongTypeException("tournament"):
+            rel.tournament = author
+
+    async def test_fk_none_assignment(self):
+        manager = await testmodels.Employee.create(name="Manager")
+        employee = await testmodels.Employee.create(name="Employee", manager=manager)
+
+        employee.manager = None
+        await employee.save()
+        self.assertIsNone(employee.manager)
+
+    async def test_fk_update_wrong_type(self):
+        tour = await testmodels.Tournament.create(name="Team1")
+        rel = await testmodels.MinRelation.create(tournament=tour)
+        author = await testmodels.Author.create(name="Author1")
+
+        with self.assertRaisesWrongTypeException("tournament"):
+            await testmodels.MinRelation.filter(id=rel.id).update(tournament=author)
+
+    async def test_fk_bulk_create_wrong_type(self):
+        author = await testmodels.Author.create(name="Author")
+        with self.assertRaisesWrongTypeException("tournament"):
+            await testmodels.MinRelation.bulk_create(
+                [testmodels.MinRelation(tournament=author) for _ in range(10)]
+            )
+
+    async def test_fk_bulk_update_wrong_type(self):
+        tour = await testmodels.Tournament.create(name="Team1")
+        await testmodels.MinRelation.bulk_create(
+            [testmodels.MinRelation(tournament=tour) for _ in range(1, 10)]
+        )
+        author = await testmodels.Author.create(name="Author")
+
+        with self.assertRaisesWrongTypeException("tournament"):
+            relations = await testmodels.MinRelation.all()
+            await testmodels.MinRelation.bulk_update(
+                [testmodels.MinRelation(id=rel.id, tournament=author) for rel in relations],
+                fields=["tournament"],
+            )

tortoise/models.py

@@ -30,11 +30,13 @@
 from tortoise.exceptions import (
     ConfigurationError,
     DoesNotExist,
+    FieldError,
     IncompleteInstanceError,
     IntegrityError,
     ObjectDoesNotExistError,
     OperationalError,
     ParamsError,
+    ValidationError,
 )
 from tortoise.expressions import Expression
 from tortoise.fields.base import Field
@@ -685,6 +687,8 @@ def __setattr__(self, key, value) -> None:
         # set field value override async default function
         if hasattr(self, "_await_when_save"):
             self._await_when_save.pop(key, None)
+        if key in self._meta.fk_fields or key in self._meta.o2o_fields:
+            self._validate_relation_type(key, value)
         super().__setattr__(key, value)
 
     def _set_kwargs(self, kwargs: dict) -> Set[str]:
@@ -806,6 +810,27 @@ def _set_pk_val(self, value: Any) -> None:
     Can be used as a field name when doing filtering e.g. ``.filter(pk=...)`` etc...
     """
 
+    @classmethod
+    def _validate_relation_type(cls, field_key: str, value: Optional["Model"]) -> None:
+        if value is None:
+            return
+
+        field = cls._meta.fields_map[field_key]
+        if not isinstance(field, (OneToOneFieldInstance, ForeignKeyFieldInstance)):
+            raise FieldError(
+                f"Field '{field_key}' must be a OneToOne or ForeignKey relation, "
+                f"got {type(field).__name__}"
+            )
+
+        expected_model = field.related_model
+        received_model = type(value)
+        if received_model is not expected_model:
+            raise ValidationError(
+                f"Invalid type for relationship field '{field_key}'. "
+                f"Expected model type '{expected_model.__name__}', but got '{received_model.__name__}'. "
+                "Make sure you're using the correct model class for this relationship."
+            )
+
     @classmethod
     async def _getbypk(cls: Type[MODEL], key: Any) -> MODEL:
         try:

tortoise/queryset.py

@@ -1204,6 +1204,7 @@ def _make_query(self) -> None:
             if field_object.pk:
                 raise IntegrityError(f"Field {key} is PK and can not be updated")
             if isinstance(field_object, (ForeignKeyFieldInstance, OneToOneFieldInstance)):
+                self.model._validate_relation_type(key, value)
                 fk_field: str = field_object.source_field  # type: ignore
                 db_field = self.model._meta.fields_map[fk_field].source_field
                 value = executor.column_map[fk_field](