Replace models.Model annotations with type variables (#603)

* Replace models.Model annotations with type variables

* Adds generic type args to generic views

* Adds more tests

* Revert "Adds generic type args to generic views"

This reverts commit 6522f30cdb9027483f46d77167394c84eb7b7f4b.

* Adds Generic support for DetailView and ListView

Co-authored-by: sobolevn <mail@sobolevn.me>

django-stubs/contrib/admin/views/decorators.pyi

@@ -1,6 +1,7 @@
 from typing import Callable, Optional, TypeVar, overload
 
 _C = TypeVar("_C", bound=Callable)
+
 @overload
 def staff_member_required(
     view_func: _C = ..., redirect_field_name: Optional[str] = ..., login_url: str = ...

django-stubs/utils/encoding.pyi

@@ -12,6 +12,7 @@ class DjangoUnicodeDecodeError(UnicodeDecodeError):
 _P = TypeVar("_P", bound=Promise)
 _S = TypeVar("_S", bound=str)
 _PT = TypeVar("_PT", None, int, float, Decimal, datetime.datetime, datetime.date, datetime.time)
+
 @overload
 def smart_text(s: _P, encoding: str = ..., strings_only: bool = ..., errors: str = ...) -> _P: ...
 @overload
@@ -40,6 +41,7 @@ def force_bytes(s: Any, encoding: str = ..., strings_only: bool = ..., errors: s
 
 smart_str = smart_text
 force_str = force_text
+
 @overload
 def iri_to_uri(iri: None) -> None: ...
 @overload

django-stubs/utils/safestring.pyi

@@ -18,6 +18,7 @@ class SafeText(str, SafeData):
 SafeString = SafeText
 
 _C = TypeVar("_C", bound=Callable)
+
 @overload
 def mark_safe(s: _SD) -> _SD: ...
 @overload

django-stubs/views/generic/detail.pyi

@@ -1,28 +1,30 @@
-from typing import Any, Optional, Type
+from typing import Any, Generic, Optional, Type, TypeVar
 
 from django.views.generic.base import ContextMixin, TemplateResponseMixin, View
 
 from django.db import models
 from django.http import HttpRequest, HttpResponse
 
-class SingleObjectMixin(ContextMixin):
-    model: Type[models.Model] = ...
-    queryset: models.query.QuerySet = ...
+T = TypeVar("T", bound=models.Model)
+
+class SingleObjectMixin(Generic[T], ContextMixin):
+    model: Type[T] = ...
+    queryset: models.query.QuerySet[T] = ...
     slug_field: str = ...
     context_object_name: str = ...
     slug_url_kwarg: str = ...
     pk_url_kwarg: str = ...
     query_pk_and_slug: bool = ...
-    def get_object(self, queryset: Optional[models.query.QuerySet] = ...) -> models.Model: ...
-    def get_queryset(self) -> models.query.QuerySet: ...
+    def get_object(self, queryset: Optional[models.query.QuerySet] = ...) -> T: ...
+    def get_queryset(self) -> models.query.QuerySet[T]: ...
     def get_slug_field(self) -> str: ...
     def get_context_object_name(self, obj: Any) -> Optional[str]: ...
 
-class BaseDetailView(SingleObjectMixin, View):
+class BaseDetailView(SingleObjectMixin[T], View):
     def get(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse: ...
 
 class SingleObjectTemplateResponseMixin(TemplateResponseMixin):
     template_name_field: Optional[str] = ...
     template_name_suffix: str = ...
 
-class DetailView(SingleObjectTemplateResponseMixin, BaseDetailView): ...
+class DetailView(SingleObjectTemplateResponseMixin, BaseDetailView[T]): ...

django-stubs/views/generic/list.pyi

@@ -1,4 +1,4 @@
-from typing import Any, Optional, Sequence, Tuple, Type
+from typing import Any, Generic, Optional, Sequence, Tuple, Type, TypeVar
 
 from django.core.paginator import Paginator
 from django.db.models.query import QuerySet, _BaseQuerySet
@@ -7,19 +7,23 @@ from django.views.generic.base import ContextMixin, TemplateResponseMixin, View
 from django.db.models import Model
 from django.http import HttpRequest, HttpResponse
 
-class MultipleObjectMixin(ContextMixin):
+T = TypeVar("T", bound=Model)
+
+class MultipleObjectMixin(Generic[T], ContextMixin):
     allow_empty: bool = ...
-    queryset: Optional[QuerySet] = ...
-    model: Optional[Type[Model]] = ...
+    queryset: Optional[QuerySet[T]] = ...
+    model: Optional[Type[T]] = ...
     paginate_by: int = ...
     paginate_orphans: int = ...
     context_object_name: Optional[str] = ...
     paginator_class: Type[Paginator] = ...
     page_kwarg: str = ...
     ordering: Sequence[str] = ...
-    def get_queryset(self) -> QuerySet: ...
+    def get_queryset(self) -> QuerySet[T]: ...
     def get_ordering(self) -> Sequence[str]: ...
-    def paginate_queryset(self, queryset: _BaseQuerySet, page_size: int) -> Tuple[Paginator, int, QuerySet, bool]: ...
+    def paginate_queryset(
+        self, queryset: _BaseQuerySet, page_size: int
+    ) -> Tuple[Paginator, int, QuerySet[T], bool]: ...
     def get_paginate_by(self, queryset: _BaseQuerySet) -> Optional[int]: ...
     def get_paginator(
         self, queryset: QuerySet, per_page: int, orphans: int = ..., allow_empty_first_page: bool = ..., **kwargs: Any
@@ -28,10 +32,10 @@ class MultipleObjectMixin(ContextMixin):
     def get_allow_empty(self) -> bool: ...
     def get_context_object_name(self, object_list: _BaseQuerySet) -> Optional[str]: ...
 
-class BaseListView(MultipleObjectMixin, View):
+class BaseListView(MultipleObjectMixin[T], View):
     def get(self, request: HttpRequest, *args: Any, **kwargs: Any) -> HttpResponse: ...
 
 class MultipleObjectTemplateResponseMixin(TemplateResponseMixin):
     template_name_suffix: str = ...
 
-class ListView(MultipleObjectTemplateResponseMixin, BaseListView): ...
+class ListView(MultipleObjectTemplateResponseMixin, BaseListView[T]): ...

tests/typecheck/views/generic/test_detail.yml

@@ -0,0 +1,55 @@
+-   case: generic_detail_view
+    main: |
+        from django.views.generic import DetailView
+        from django.db.models import QuerySet
+
+        from myapp.models import MyModel
+
+        class MyDetailView(DetailView[MyModel]):
+            model = MyModel
+            queryset = MyModel.objects.all()
+
+            def get_queryset(self) -> QuerySet[MyModel]:
+                self.get_object(super().get_queryset())
+                return super().get_queryset()
+    custom_settings: |
+        INSTALLED_APPS = ('myapp',)
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+                class MyModel(models.Model):
+                    ...
+
+
+-   case: generic_detail_view_wrong
+    main: |
+        from django.views.generic import DetailView
+        from django.db.models import QuerySet
+
+        from myapp.models import MyModel, Other
+
+        class MyDetailView(DetailView[Other]):
+            model = MyModel
+            queryset = MyModel.objects.all()
+
+            def get_queryset(self) -> QuerySet[MyModel]:
+                self.get_object(super().get_queryset())
+                return super().get_queryset()
+    custom_settings: |
+        INSTALLED_APPS = ('myapp',)
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+                class MyModel(models.Model):
+                    ...
+                class Other(models.Model):
+                    ...
+    out: |
+      main:7: error: Incompatible types in assignment (expression has type "Type[MyModel]", base class "SingleObjectMixin" defined the type as "Type[Other]")
+      main:8: error: Incompatible types in assignment (expression has type "Manager[MyModel]", base class "SingleObjectMixin" defined the type as "QuerySet[Other]")
+      main:10: error: Return type "QuerySet[MyModel]" of "get_queryset" incompatible with return type "QuerySet[Other]" in supertype "SingleObjectMixin"
+      main:12: error: Incompatible return value type (got "QuerySet[Other]", expected "QuerySet[MyModel]")

tests/typecheck/views/generic/test_list.yml

@@ -0,0 +1,52 @@
+-   case: generic_list_view
+    main: |
+        from django.views.generic import ListView
+        from django.db.models import QuerySet
+
+        from myapp.models import MyModel
+
+        class MyListView(ListView[MyModel]):
+            model = MyModel
+            queryset = MyModel.objects.all()
+
+            def get_queryset(self) -> QuerySet[MyModel]:
+                ...
+    custom_settings: |
+        INSTALLED_APPS = ('myapp',)
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+                class MyModel(models.Model):
+                    ...
+
+
+-   case: generic_list_view_wrong
+    main: |
+        from django.views.generic import ListView
+        from django.db.models import QuerySet
+
+        from myapp.models import MyModel, Other
+
+        class MyListView(ListView[Other]):
+            model = MyModel
+            queryset = MyModel.objects.all()
+
+            def get_queryset(self) -> QuerySet[MyModel]:
+                ...
+    custom_settings: |
+        INSTALLED_APPS = ('myapp',)
+    files:
+        -   path: myapp/__init__.py
+        -   path: myapp/models.py
+            content: |
+                from django.db import models
+                class MyModel(models.Model):
+                    ...
+                class Other(models.Model):
+                    ...
+    out: |
+      main:7: error: Incompatible types in assignment (expression has type "Type[MyModel]", base class "MultipleObjectMixin" defined the type as "Optional[Type[Other]]")
+      main:8: error: Incompatible types in assignment (expression has type "Manager[MyModel]", base class "MultipleObjectMixin" defined the type as "Optional[QuerySet[Other]]")
+      main:10: error: Return type "QuerySet[MyModel]" of "get_queryset" incompatible with return type "QuerySet[Other]" in supertype "MultipleObjectMixin"