Add TypeVar resolution for as_manager and from_queryset querysets (#1646

)

mypy_django_plugin/transformers/managers.py

@@ -18,7 +18,7 @@
 from mypy.plugin import AttributeContext, ClassDefContext, DynamicClassDefContext
 from mypy.semanal import SemanticAnalyzer
 from mypy.semanal_shared import has_placeholder
-from mypy.types import AnyType, CallableType, Instance, ProperType, TypeOfAny
+from mypy.types import AnyType, CallableType, Instance, ProperType, TypeOfAny, TypeVarType
 from mypy.types import Type as MypyType
 from mypy.typevars import fill_typevars
 
@@ -105,6 +105,8 @@ def get_funcdef_type(definition: Union[FuncBase, Decorator, None]) -> Optional[P
             ret_type = Instance(queryset_info, [manager_instance.args[0], manager_instance.args[0]])
         variables = []
 
+    ret_type = _find_type_var_from_mro(ret_type, queryset_info)
+
     # Drop any 'self' argument as our manager is already initialized
     return method_type.copy_modified(
         arg_types=method_type.arg_types[1:],
@@ -115,6 +117,66 @@ def get_funcdef_type(definition: Union[FuncBase, Decorator, None]) -> Optional[P
     )
 
 
+def _get_base_containing_method(queryset_info: TypeInfo, method_name: str) -> Instance | None:
+    for mro in queryset_info.mro:
+        for base in mro.bases:
+            if method_name in base.type.names:
+                return base
+    return None
+
+
+def _manage_type_var(ret_type: MypyType, base: Instance) -> MypyType:
+    """
+    Attempts to manage the concrete type corresponding to a `TypeVarType` in a class's base types.
+    If nothing is found, keep it unchanged.
+
+    Example:
+
+    T = TypeVar("T")
+    for def example_list_dict(self) -> list[dict[str, T]]
+
+    Tries to find the corresponding `TypeVar` of `T` if it has been set.
+
+    """
+    if isinstance(ret_type, TypeVarType):
+        return _find_type_var(base, ret_type) or ret_type
+    elif isinstance(ret_type, Instance):
+        # Since it is an instance, recursively find the type var for all its args.
+        ret_type.args = tuple(_manage_type_var(item, base) for item in ret_type.args)
+    if isinstance(ret_type, ProperType) and hasattr(ret_type, "item"):
+        # For example TypeType has an item. find the type_var for this item
+        ret_type.item = _manage_type_var(ret_type.item, base)
+    if isinstance(ret_type, ProperType) and hasattr(ret_type, "items"):
+        # For example TypeList has items. find recursively type_var for its items
+        ret_type.items = [_manage_type_var(item, base) for item in ret_type.items]
+    return ret_type
+
+
+def _find_type_var(base: Instance, target: TypeVarType) -> Optional[MypyType]:
+    """
+    Attempts to find the concrete type corresponding to a TypeVarType in a class's base types.
+
+    Example:
+    Suppose queryset_info is based on a generic class `QuerySet[T]` and ret_type corresponds
+    to `T`, then this function will return the concrete type that `T` was instantiated with.
+    """
+    for i, type_var in enumerate(base.type.defn.type_vars):
+        if type_var.fullname == target.fullname:
+            return base.args[i]
+    return None
+
+
+def _find_type_var_from_mro(ret_type: MypyType, queryset_info: TypeInfo) -> Optional[MypyType]:
+    """
+    Attempts to find the type var by looking at the mro elements (reversed).
+    """
+    new_ret_type = ret_type
+    for i, mro in enumerate(reversed(queryset_info.mro)):
+        for base in mro.bases:
+            new_ret_type = _manage_type_var(new_ret_type, base)
+    return new_ret_type or ret_type
+
+
 def get_method_type_from_reverse_manager(
     api: TypeChecker, method_name: str, manager_type_info: TypeInfo
 ) -> Optional[ProperType]:

tests/typecheck/managers/querysets/test_as_manager.yml

@@ -146,6 +146,105 @@
                 class MyModel(models.Model):
                     objects = ManagerFromModelQuerySet
 
+-   case: handles_subclasses_of_subclasses_of_queryset
+    main: |
+        from myapp.models import MyModel
+        reveal_type(MyModel.objects.example())  # N: Revealed type is "myapp.models.MyModel"
+        reveal_type(MyModel.objects.example_2())  # N: Revealed type is "myapp.models.MyModel"
+        reveal_type(MyModel.objects.override())  # N: Revealed type is "myapp.models.MyModel"
+        reveal_type(MyModel.objects.override2())  # N: Revealed type is "myapp.models.MyModel"
+        reveal_type(MyModel.objects.dummy_override())  # N: Revealed type is "myapp.models.MyModel"
+
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from typing import TypeVar
+                from django.db import models
+
+                _CTE = TypeVar("_CTE", bound=models.Model)
+                _CTE_2 = TypeVar("_CTE_2", bound=models.Model)
+
+                class _MyModelQuerySet(models.QuerySet[_CTE]):
+                    def example(self) -> _CTE: ...
+                    def override(self) -> _CTE: ...
+                    def override2(self) -> _CTE: ...
+                    def dummy_override(self) -> int: ...
+
+                class _MyModelQuerySet2(_MyModelQuerySet[_CTE_2]):
+                    def example_2(self) -> _CTE_2: ...
+                    def override(self) -> _CTE_2: ...
+                    def override2(self) -> _CTE_2: ...
+                    def dummy_override(self) -> _CTE_2: ...  # type: ignore[override]
+
+                class MyModelQuerySet(_MyModelQuerySet2["MyModel"]):
+                    def override(self) -> "MyModel": ...
+
+                class MyModel(models.Model):
+                    objects = MyModelQuerySet.as_manager()
+
+-   case: handles_subclasses_of_queryset
+    main: |
+        from myapp.models import MyModel, BaseQuerySet
+        reveal_type(MyModel.objects.example())  # N: Revealed type is "myapp.models.MyModel"
+        reveal_type(MyModel.objects.example_2())  # N: Revealed type is "myapp.models.MyOtherModel"
+        reveal_type(MyModel.objects.example_list())  # N: Revealed type is "builtins.list[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_type())  # N: Revealed type is "Type[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_tuple_simple())  # N: Revealed type is "Tuple[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_tuple_list())  # N: Revealed type is "builtins.tuple[myapp.models.MyModel, ...]"
+        reveal_type(MyModel.objects.example_tuple_double())  # N: Revealed type is "Tuple[builtins.int, myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_class())  # N: Revealed type is "myapp.models.Example[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_type_class())  # N: Revealed type is "Type[myapp.models.Example[myapp.models.MyModel]]"
+        reveal_type(MyModel.objects.example_collection())  # N: Revealed type is "typing.Collection[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_set())  # N: Revealed type is "builtins.set[myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_dict())  # N: Revealed type is "builtins.dict[builtins.str, myapp.models.MyModel]"
+        reveal_type(MyModel.objects.example_list_dict())  # N: Revealed type is "builtins.list[builtins.dict[myapp.models.MyOtherModel, myapp.models.MyModel]]"
+        class TestQuerySet(BaseQuerySet[str, MyModel]): ... # E: Type argument "str" of "BaseQuerySet" must be a subtype of "Model"
+        reveal_type(MyModel.objects.example_t(5))  # N: Revealed type is "builtins.int"
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from typing import TypeVar, Generic, Collection
+
+                from django.db import models
+
+                _CTE = TypeVar("_CTE", bound=models.Model)
+                _CTE_2 = TypeVar("_CTE_2", bound=models.Model)
+                T = TypeVar("T")
+
+                class Example(Generic[_CTE]): ...
+
+                class BaseQuerySet(models.QuerySet[_CTE], Generic[_CTE, _CTE_2]):
+
+                    def example(self) -> _CTE: ...
+                    def example_2(self) -> _CTE_2: ...
+                    def example_list(self) -> list[_CTE]: ...
+                    def example_type(self) -> type[_CTE]: ...
+                    def example_tuple_simple(self) -> tuple[_CTE]: ...
+                    def example_tuple_list(self) -> tuple[_CTE, ...]: ...
+                    def example_tuple_double(self) -> tuple[int, _CTE]: ...
+                    def example_class(self) -> Example[_CTE]: ...
+                    def example_type_class(self) -> type[Example[_CTE]]: ...
+                    def example_collection(self) -> Collection[_CTE]: ...
+                    def example_set(self) -> set[_CTE]: ...
+                    def example_dict(self) -> dict[str, _CTE]: ...
+                    def example_list_dict(self) -> list[dict[_CTE_2, _CTE]]: ...
+                    def example_t(self, a: T) -> T: ...
+
+
+                class MyModelQuerySet(BaseQuerySet["MyModel", "MyOtherModel"]):
+                    ...
+
+                class MyModel(models.Model):
+                    objects = MyModelQuerySet.as_manager()
+
+                class MyOtherModel(models.Model): ...
+
 -   case: reuses_generated_type_when_called_identically_for_multiple_managers
     main: |
         from myapp.models import MyModel

tests/typecheck/managers/querysets/test_from_queryset.yml

@@ -70,6 +70,41 @@
                 NewManager = BaseManager.from_queryset(ModelQuerySet)
                 class MyModel(models.Model):
                     objects = NewManager()
+-   case: handles_subclasses_of_queryset
+    main: |
+        from myapp.models import MyModel
+        reveal_type(MyModel.objects.example())  # N: Revealed type is "myapp.models.MyModel"
+    installed_apps:
+        - myapp
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/querysets.py
+            content: |
+                from typing import TypeVar, TYPE_CHECKING
+
+                from django.db import models
+                from django.db.models.manager import BaseManager
+                if TYPE_CHECKING:
+                    from .models import MyModel
+
+                _CTE = TypeVar("_CTE", bound=models.Model)
+
+                class _MyModelQuerySet(models.QuerySet[_CTE]):
+
+                    def example(self) -> _CTE: ...
+
+                class MyModelQuerySet(_MyModelQuerySet["MyModel"]):
+                    ...
+
+        - path: myapp/models.py
+          content: |
+            from django.db import models
+            from django.db.models.manager import BaseManager
+            from .querysets import MyModelQuerySet
+
+            NewManager = BaseManager.from_queryset(MyModelQuerySet)
+            class MyModel(models.Model):
+                objects = NewManager()
 
 -   case: from_queryset_generated_manager_imported_from_other_module
     main: |