Fix crash when constructing an abstract model with recursive relation (…

…typeddjango#1393)

django-stubs/db/models/fields/__init__.pyi

@@ -3,7 +3,7 @@ import uuid
 from collections.abc import Callable, Iterable, Sequence
 from datetime import date, time, timedelta
 from datetime import datetime as real_datetime
-from typing import Any, ClassVar, Generic, Protocol, TypeVar, overload
+from typing import Any, ClassVar, Generic, Literal, Protocol, TypeVar, overload
 
 from django.core import validators  # due to weird mypy.stubtest error
 from django.core.checks import CheckMessage
@@ -122,7 +122,7 @@ class Field(RegisterLookupMixin, Generic[_ST, _GT]):
     primary_key: bool
     remote_field: ForeignObjectRel | None
     is_relation: bool
-    related_model: type[Model] | None
+    related_model: type[Model] | Literal["self"] | None
     one_to_many: bool | None
     one_to_one: bool | None
     many_to_many: bool | None

django-stubs/db/models/fields/related.pyi

@@ -43,7 +43,7 @@ class RelatedField(FieldCacheMixin, Field[_ST, _GT]):
     rel_class: type[ForeignObjectRel]
     swappable: bool
     @property
-    def related_model(self) -> type[Model]: ...  # type: ignore
+    def related_model(self) -> type[Model] | Literal["self"]: ...  # type: ignore
     def get_forward_related_filter(self, obj: Model) -> dict[str, int | UUID]: ...
     def get_reverse_related_filter(self, obj: Model) -> Q: ...
     @property

django-stubs/db/models/fields/reverse_related.pyi

@@ -51,7 +51,7 @@ class ForeignObjectRel(FieldCacheMixin):
     @property
     def target_field(self) -> AutoField: ...
     @property
-    def related_model(self) -> type[Model]: ...
+    def related_model(self) -> type[Model] | Literal["self"]: ...
     @property
     def many_to_many(self) -> bool: ...
     @property

mypy_django_plugin/django/context.py

@@ -206,6 +206,9 @@ def get_field_set_type_from_model_type_info(info: Optional[TypeInfo], field_name
         for field in model_cls._meta.get_fields():
             if isinstance(field, Field):
                 field_name = field.attname
+                # Can not determine target_field for recursive relationship when model is abstract
+                if field.related_model == "self" and model_cls._meta.abstract:
+                    continue
                 # Try to retrieve set type from a model's TypeInfo object and fallback to retrieving it manually
                 # from django-stubs own declaration. This is to align with the setter types declared for
                 # assignment.

mypy_django_plugin/lib/helpers.py

@@ -217,7 +217,8 @@ def get_private_descriptor_type(type_info: TypeInfo, private_field_name: str, is
 
 def get_field_lookup_exact_type(api: TypeChecker, field: "Field[Any, Any]") -> MypyType:
     if isinstance(field, (RelatedField, ForeignObjectRel)):
-        lookup_type_class = field.related_model
+        # Not using field.related_model because that may have str value "self"
+        lookup_type_class = field.remote_field.model
         rel_model_info = lookup_class_typeinfo(api, lookup_type_class)
         if rel_model_info is None:
             return AnyType(TypeOfAny.from_error)

tests/typecheck/models/test_abstract.yml

@@ -41,3 +41,33 @@
 
             class MyModel(BaseModel):
                 field = models.IntegerField()
+
+- case: test_can_instantiate_with_recursive_relation_on_abstract_model
+  main: |
+    from myapp.models import Concrete, Recursive
+    first = Concrete.objects.create(parent=None)
+    Concrete.objects.create(parent=first)
+    Recursive.objects.create(parent=None)
+    Recursive(parent=Recursive(parent=None))
+    Concrete(parent=Concrete(parent=None))
+  out: |
+    main:4: error: Unexpected attribute "parent" for model "Recursive"
+    main:4: error: Cannot instantiate abstract model "Recursive"
+    main:5: error: Unexpected attribute "parent" for model "Recursive"
+    main:5: error: Cannot instantiate abstract model "Recursive"
+  installed_apps:
+    - myapp
+  files:
+    -   path: myapp/__init__.py
+    -   path: myapp/models.py
+        content: |
+            from django.db import models
+
+            class Recursive(models.Model):
+                parent = models.ForeignKey("self", null=True, on_delete=models.CASCADE)
+
+                class Meta:
+                    abstract = True
+
+            class Concrete(Recursive):
+                ...