Improve get_context_object_name on SingleObjectMixin and MultipleObjectMixin (#2298)

Author: flaeppe

django-stubs/views/generic/detail.pyi

@@ -1,4 +1,4 @@
-from typing import Any, Generic, TypeVar
+from typing import Any, Generic, TypeVar, overload
 
 from django.db import models
 from django.http import HttpRequest, HttpResponse
@@ -17,7 +17,10 @@ class SingleObjectMixin(Generic[_M], ContextMixin):
     def get_object(self, queryset: models.query.QuerySet[_M] | None = ...) -> _M: ...
     def get_queryset(self) -> models.query.QuerySet[_M]: ...
     def get_slug_field(self) -> str: ...
-    def get_context_object_name(self, obj: _M) -> str | None: ...
+    @overload
+    def get_context_object_name(self, obj: _M) -> str: ...
+    @overload
+    def get_context_object_name(self, obj: Any) -> str | None: ...
 
 class BaseDetailView(SingleObjectMixin[_M], View):
     object: _M

django-stubs/views/generic/list.pyi

@@ -1,12 +1,17 @@
 from collections.abc import Sequence
-from typing import Any, Generic, TypeVar
+from typing import Any, Generic, Protocol, TypeVar, overload, type_check_only
 
 from django.core.paginator import Page, Paginator, _SupportsPagination
 from django.db.models import Model, QuerySet
 from django.http import HttpRequest, HttpResponse
 from django.views.generic.base import ContextMixin, TemplateResponseMixin, View
 
-_M = TypeVar("_M", bound=Model, covariant=True)
+_M = TypeVar("_M", bound=Model)
+
+@type_check_only
+class _HasModel(Protocol):
+    @property
+    def model(self) -> type[Model]: ...
 
 class MultipleObjectMixin(Generic[_M], ContextMixin):
     allow_empty: bool
@@ -34,7 +39,10 @@ class MultipleObjectMixin(Generic[_M], ContextMixin):
     ) -> Paginator: ...
     def get_paginate_orphans(self) -> int: ...
     def get_allow_empty(self) -> bool: ...
-    def get_context_object_name(self, object_list: _SupportsPagination[_M]) -> str | None: ...
+    @overload
+    def get_context_object_name(self, object_list: _HasModel) -> str: ...
+    @overload
+    def get_context_object_name(self, object_list: Any) -> str | None: ...
     def get_context_data(
         self, *, object_list: _SupportsPagination[_M] | None = ..., **kwargs: Any
     ) -> dict[str, Any]: ...

tests/assert_type/views/generic.py

@@ -0,0 +1,30 @@
+from typing import Optional, Type
+
+from django.db import models
+from django.views.generic.detail import SingleObjectMixin
+from django.views.generic.list import ListView
+from typing_extensions import assert_type
+
+
+class MyModel(models.Model): ...
+
+
+class MyDetailView(SingleObjectMixin[MyModel]): ...
+
+
+detail_view = MyDetailView()
+assert_type(detail_view.model, Type[MyModel])
+assert_type(detail_view.queryset, Optional[models.QuerySet[MyModel, MyModel]])
+assert_type(detail_view.get_context_object_name(MyModel()), str)
+assert_type(detail_view.get_context_object_name(1), Optional[str])
+
+
+class MyListView(ListView[MyModel]): ...
+
+
+list_view = MyListView()
+assert_type(list_view.model, Optional[Type[MyModel]])
+assert_type(list_view.queryset, Optional[models.QuerySet[MyModel, MyModel]])
+assert_type(list_view.get_context_object_name(models.QuerySet[MyModel]()), str)
+assert_type(list_view.get_context_object_name(MyModel()), Optional[str])
+assert_type(list_view.get_context_object_name(1), Optional[str])

tests/typecheck/views/generic/test_detail.yml

@@ -37,8 +37,8 @@
             def get_queryset(self) -> QuerySet[MyModel]:
                 self.get_object(super().get_queryset())
                 return super().get_queryset()
-    custom_settings: |
-        INSTALLED_APPS = ('myapp',)
+    installed_apps:
+        - myapp
     files:
         -   path: myapp/__init__.py
         -   path: myapp/models.py