Add state attribute to Model (#347) (#348)

Add from_db method to Model

Co-authored-by: Stevan Milic <stevan.milic@tradecore.com>

django-stubs/db/models/base.pyi

@@ -7,6 +7,13 @@ from django.db.models.options import Options
 
 _Self = TypeVar("_Self", bound="Model")
 
+class ModelStateFieldsCacheDescriptor: ...
+
+class ModelState:
+    db: Optional[str] = ...
+    adding: bool = ...
+    fields_cache: ModelStateFieldsCacheDescriptor = ...
+
 class ModelBase(type): ...
 
 class Model(metaclass=ModelBase):
@@ -17,7 +24,10 @@ class Model(metaclass=ModelBase):
     _default_manager: BaseManager[Model]
     objects: BaseManager[Any]
     pk: Any = ...
+    _state: ModelState
     def __init__(self: _Self, *args, **kwargs) -> None: ...
+    @classmethod
+    def from_db(cls, db: Optional[str], field_names: Collection[str], values: Collection[Any]) -> _Self: ...
     def delete(self, using: Any = ..., keep_parents: bool = ...) -> Tuple[int, Dict[str, int]]: ...
     def full_clean(self, exclude: Optional[Collection[str]] = ..., validate_unique: bool = ...) -> None: ...
     def clean(self) -> None: ...
@@ -46,10 +56,3 @@ class Model(metaclass=ModelBase):
     @classmethod
     def check(cls, **kwargs: Any) -> List[CheckMessage]: ...
     def __getstate__(self) -> dict: ...
-
-class ModelStateFieldsCacheDescriptor: ...
-
-class ModelState:
-    db: None = ...
-    adding: bool = ...
-    fields_cache: ModelStateFieldsCacheDescriptor = ...

test-data/typecheck/models/test_state.yml

@@ -0,0 +1,14 @@
+-   case: state_attribute_has_a_type_of_model_state
+    main: |
+        from myapp.models import MyUser
+        user = MyUser(pk=1)
+        reveal_type(user._state)  # N: Revealed type is 'django.db.models.base.ModelState'
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+                class MyUser(models.Model):
+                    pass