make BaseModelAdmin generic to properly type methods dealing with models (#504)

* make BaseModelAdmin generic to properly type the `obj` argument of ModelAdmin.delete_model
closes #482

* turn BaseModelAdmin into bound generic, run black

* add test for generic ModelAdmin

django-stubs/contrib/admin/options.pyi

@@ -1,5 +1,20 @@
 from collections import OrderedDict
-from typing import Any, Callable, Dict, Iterator, List, Optional, Sequence, Set, Tuple, Type, Union, Mapping, TypeVar
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Generic,
+    Iterator,
+    List,
+    Optional,
+    Sequence,
+    Set,
+    Tuple,
+    Type,
+    Union,
+    Mapping,
+    TypeVar,
+)
 
 from django.forms.forms import BaseForm
 from django.forms.formsets import BaseFormSet
@@ -57,7 +72,11 @@ _T = TypeVar("_T")
 _ListOrTuple = Union[Tuple[_T, ...], List[_T]]
 _FieldsetSpec = _ListOrTuple[Tuple[Optional[str], _FieldOpts]]
 
-class BaseModelAdmin:
+# Generic type specifically for models, for use in BaseModelAdmin and subclasses
+# https://github.com/typeddjango/django-stubs/issues/482
+_ModelT = TypeVar("_ModelT", bound=Model)
+
+class BaseModelAdmin(Generic[_ModelT]):
     autocomplete_fields: Sequence[str] = ...
     raw_id_fields: Sequence[str] = ...
     fields: Sequence[Union[str, Sequence[str]]] = ...
@@ -69,7 +88,7 @@ class BaseModelAdmin:
     radio_fields: Mapping[str, _Direction] = ...
     prepopulated_fields: Mapping[str, Sequence[str]] = ...
     formfield_overrides: Mapping[Type[Field], Mapping[str, Any]] = ...
-    readonly_fields: Sequence[Union[str, Callable[[Model], Any]]] = ...
+    readonly_fields: Sequence[Union[str, Callable[[_ModelT], Any]]] = ...
     ordering: Sequence[str] = ...
     sortable_by: Sequence[str] = ...
     view_on_site: bool = ...
@@ -92,28 +111,28 @@ class BaseModelAdmin:
         self, db_field: ManyToManyField, request: Optional[HttpRequest], **kwargs: Any
     ) -> ModelMultipleChoiceField: ...
     def get_autocomplete_fields(self, request: HttpRequest) -> Tuple: ...
-    def get_view_on_site_url(self, obj: Optional[Model] = ...) -> Optional[str]: ...
+    def get_view_on_site_url(self, obj: Optional[_ModelT] = ...) -> Optional[str]: ...
     def get_empty_value_display(self) -> SafeText: ...
-    def get_exclude(self, request: HttpRequest, obj: Optional[Model] = ...) -> Any: ...
-    def get_fields(self, request: HttpRequest, obj: Optional[Model] = ...) -> Sequence[Union[Callable, str]]: ...
+    def get_exclude(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> Any: ...
+    def get_fields(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> Sequence[Union[Callable, str]]: ...
     def get_fieldsets(
-        self, request: HttpRequest, obj: Optional[Model] = ...
+        self, request: HttpRequest, obj: Optional[_ModelT] = ...
     ) -> List[Tuple[Optional[str], Dict[str, Any]]]: ...
     def get_ordering(self, request: HttpRequest) -> Union[List[str], Tuple]: ...
-    def get_readonly_fields(self, request: HttpRequest, obj: Optional[Model] = ...) -> Union[List[str], Tuple]: ...
-    def get_prepopulated_fields(self, request: HttpRequest, obj: Optional[Model] = ...) -> Dict[str, Tuple[str]]: ...
+    def get_readonly_fields(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> Union[List[str], Tuple]: ...
+    def get_prepopulated_fields(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> Dict[str, Tuple[str]]: ...
     def get_queryset(self, request: HttpRequest) -> QuerySet: ...
     def get_sortable_by(self, request: HttpRequest) -> Union[List[Callable], List[str], Tuple]: ...
     def lookup_allowed(self, lookup: str, value: str) -> bool: ...
     def to_field_allowed(self, request: HttpRequest, to_field: str) -> bool: ...
     def has_add_permission(self, request: HttpRequest) -> bool: ...
-    def has_change_permission(self, request: HttpRequest, obj: Optional[Model] = ...) -> bool: ...
-    def has_delete_permission(self, request: HttpRequest, obj: Optional[Model] = ...) -> bool: ...
-    def has_view_permission(self, request: HttpRequest, obj: Optional[Model] = ...) -> bool: ...
+    def has_change_permission(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> bool: ...
+    def has_delete_permission(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> bool: ...
+    def has_view_permission(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> bool: ...
     def has_module_permission(self, request: HttpRequest) -> bool: ...
 
-class ModelAdmin(BaseModelAdmin):
-    list_display: Sequence[Union[str, Callable[[Model], Any]]] = ...
+class ModelAdmin(BaseModelAdmin[_ModelT]):
+    list_display: Sequence[Union[str, Callable[[_ModelT], Any]]] = ...
     list_display_links: Optional[Sequence[Union[str, Callable]]] = ...
     list_filter: Sequence[Union[str, Type[ListFilter], Tuple[str, Type[ListFilter]]]] = ...
     list_select_related: Union[bool, Sequence[str]] = ...
@@ -140,24 +159,24 @@ class ModelAdmin(BaseModelAdmin):
     actions_on_top: bool = ...
     actions_on_bottom: bool = ...
     actions_selection_counter: bool = ...
-    model: Type[Model] = ...
+    model: Type[_ModelT] = ...
     opts: Options = ...
     admin_site: AdminSite = ...
-    def __init__(self, model: Type[Model], admin_site: Optional[AdminSite]) -> None: ...
-    def get_inline_instances(self, request: HttpRequest, obj: Optional[Model] = ...) -> List[InlineModelAdmin]: ...
+    def __init__(self, model: Type[_ModelT], admin_site: Optional[AdminSite]) -> None: ...
+    def get_inline_instances(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> List[InlineModelAdmin]: ...
     def get_urls(self) -> List[URLPattern]: ...
     @property
     def urls(self) -> List[URLPattern]: ...
     @property
     def media(self) -> Media: ...
     def get_model_perms(self, request: HttpRequest) -> Dict[str, bool]: ...
-    def get_form(self, request: Any, obj: Optional[Any] = ..., change: bool = ..., **kwargs: Any): ...
+    def get_form(self, request: Any, obj: Optional[_ModelT] = ..., change: bool = ..., **kwargs: Any): ...
     def get_changelist(self, request: HttpRequest, **kwargs: Any) -> Type[ChangeList]: ...
     def get_changelist_instance(self, request: HttpRequest) -> ChangeList: ...
-    def get_object(self, request: HttpRequest, object_id: str, from_field: None = ...) -> Optional[Model]: ...
+    def get_object(self, request: HttpRequest, object_id: str, from_field: None = ...) -> Optional[_ModelT]: ...
     def get_changelist_form(self, request: Any, **kwargs: Any): ...
     def get_changelist_formset(self, request: Any, **kwargs: Any): ...
-    def get_formsets_with_inlines(self, request: HttpRequest, obj: Optional[Model] = ...) -> Iterator[Any]: ...
+    def get_formsets_with_inlines(self, request: HttpRequest, obj: Optional[_ModelT] = ...) -> Iterator[Any]: ...
     def get_paginator(
         self,
         request: HttpRequest,
@@ -166,10 +185,10 @@ class ModelAdmin(BaseModelAdmin):
         orphans: int = ...,
         allow_empty_first_page: bool = ...,
     ) -> Paginator: ...
-    def log_addition(self, request: HttpRequest, object: Model, message: Any) -> LogEntry: ...
-    def log_change(self, request: HttpRequest, object: Model, message: Any) -> LogEntry: ...
-    def log_deletion(self, request: HttpRequest, object: Model, object_repr: str) -> LogEntry: ...
-    def action_checkbox(self, obj: Model) -> SafeText: ...
+    def log_addition(self, request: HttpRequest, object: _ModelT, message: Any) -> LogEntry: ...
+    def log_change(self, request: HttpRequest, object: _ModelT, message: Any) -> LogEntry: ...
+    def log_deletion(self, request: HttpRequest, object: _ModelT, object_repr: str) -> LogEntry: ...
+    def action_checkbox(self, obj: _ModelT) -> SafeText: ...
     def get_actions(self, request: HttpRequest) -> OrderedDict: ...
     def get_action_choices(
         self, request: HttpRequest, default_choices: List[Tuple[str, str]] = ...
@@ -198,8 +217,8 @@ class ModelAdmin(BaseModelAdmin):
         fail_silently: bool = ...,
     ) -> None: ...
     def save_form(self, request: Any, form: Any, change: Any): ...
-    def save_model(self, request: Any, obj: Any, form: Any, change: Any) -> None: ...
-    def delete_model(self, request: HttpRequest, obj: Model) -> None: ...
+    def save_model(self, request: Any, obj: _ModelT, form: Any, change: Any) -> None: ...
+    def delete_model(self, request: HttpRequest, obj: _ModelT) -> None: ...
     def delete_queryset(self, request: HttpRequest, queryset: QuerySet) -> None: ...
     def save_formset(self, request: Any, form: Any, formset: Any, change: Any) -> None: ...
     def save_related(self, request: Any, form: Any, formsets: Any, change: Any) -> None: ...
@@ -210,19 +229,19 @@ class ModelAdmin(BaseModelAdmin):
         add: bool = ...,
         change: bool = ...,
         form_url: str = ...,
-        obj: Optional[Any] = ...,
+        obj: Optional[_ModelT] = ...,
     ): ...
     def response_add(
-        self, request: HttpRequest, obj: Model, post_url_continue: Optional[str] = ...
+        self, request: HttpRequest, obj: _ModelT, post_url_continue: Optional[str] = ...
     ) -> HttpResponse: ...
-    def response_change(self, request: HttpRequest, obj: Model) -> HttpResponse: ...
-    def response_post_save_add(self, request: HttpRequest, obj: Model) -> HttpResponseRedirect: ...
-    def response_post_save_change(self, request: HttpRequest, obj: Model) -> HttpResponseRedirect: ...
+    def response_change(self, request: HttpRequest, obj: _ModelT) -> HttpResponse: ...
+    def response_post_save_add(self, request: HttpRequest, obj: _ModelT) -> HttpResponseRedirect: ...
+    def response_post_save_change(self, request: HttpRequest, obj: _ModelT) -> HttpResponseRedirect: ...
     def response_action(self, request: HttpRequest, queryset: QuerySet) -> Optional[HttpResponseBase]: ...
     def response_delete(self, request: HttpRequest, obj_display: str, obj_id: int) -> HttpResponse: ...
     def render_delete_form(self, request: Any, context: Any): ...
     def get_inline_formsets(
-        self, request: HttpRequest, formsets: List[Any], inline_instances: List[Any], obj: Optional[Model] = ...
+        self, request: HttpRequest, formsets: List[Any], inline_instances: List[Any], obj: Optional[_ModelT] = ...
     ) -> List[Any]: ...
     def get_changeform_initial_data(self, request: HttpRequest) -> Dict[str, str]: ...
     def changeform_view(
@@ -246,8 +265,8 @@ class ModelAdmin(BaseModelAdmin):
     def delete_view(self, request: HttpRequest, object_id: str, extra_context: None = ...) -> Any: ...
     def history_view(self, request: HttpRequest, object_id: str, extra_context: None = ...) -> HttpResponse: ...
 
-class InlineModelAdmin(BaseModelAdmin):
-    model: Type[Model] = ...
+class InlineModelAdmin(BaseModelAdmin[_ModelT]):
+    model: Type[_ModelT] = ...
     fk_name: str = ...
     formset: BaseFormSet = ...
     extra: int = ...
@@ -263,13 +282,13 @@ class InlineModelAdmin(BaseModelAdmin):
     parent_model: Any = ...
     opts: Any = ...
     has_registered_model: Any = ...
-    def __init__(self, parent_model: Union[Type[Model], Model], admin_site: AdminSite) -> None: ...
+    def __init__(self, parent_model: Union[Type[_ModelT], _ModelT], admin_site: AdminSite) -> None: ...
     @property
     def media(self) -> Media: ...
-    def get_extra(self, request: HttpRequest, obj: Optional[Model] = ..., **kwargs: Any) -> int: ...
-    def get_min_num(self, request: HttpRequest, obj: Optional[Model] = ..., **kwargs: Any) -> Optional[int]: ...
-    def get_max_num(self, request: HttpRequest, obj: Optional[Model] = ..., **kwargs: Any) -> Optional[int]: ...
-    def get_formset(self, request: Any, obj: Optional[Any] = ..., **kwargs: Any): ...
+    def get_extra(self, request: HttpRequest, obj: Optional[_ModelT] = ..., **kwargs: Any) -> int: ...
+    def get_min_num(self, request: HttpRequest, obj: Optional[_ModelT] = ..., **kwargs: Any) -> Optional[int]: ...
+    def get_max_num(self, request: HttpRequest, obj: Optional[_ModelT] = ..., **kwargs: Any) -> Optional[int]: ...
+    def get_formset(self, request: Any, obj: Optional[_ModelT] = ..., **kwargs: Any): ...
 
-class StackedInline(InlineModelAdmin): ...
-class TabularInline(InlineModelAdmin): ...
+class StackedInline(InlineModelAdmin[_ModelT]): ...
+class TabularInline(InlineModelAdmin[_ModelT]): ...

test-data/typecheck/contrib/admin/test_options.yml

@@ -14,7 +14,10 @@
       def an_action(modeladmin: admin.ModelAdmin, request: HttpRequest, queryset: QuerySet) -> None:
           pass
 
-      class A(admin.ModelAdmin):
+      class TestModel(models.Model):
+          pass
+
+      class A(admin.ModelAdmin[TestModel]):
           # BaseModelAdmin
           autocomplete_fields = ("strs",)
           raw_id_fields = ["strs"]
@@ -71,6 +74,11 @@
           actions_selection_counter = True
           admin_site = AdminSite()
 
+          # test generic ModelAdmin
+          # https://github.com/typeddjango/django-stubs/pull/504
+          # this will fail if `model` has a type other than the generic specified in the class declaration
+          model = TestModel
+
           def a_method_action(self, request, queryset):
               pass
 
@@ -127,4 +135,4 @@
           pass
 
       class A(admin.ModelAdmin):
-          actions = [an_action]  # E: List item 0 has incompatible type "Callable[[None], None]"; expected "Union[Callable[[ModelAdmin, HttpRequest, QuerySet[Any]], None], str]"
+          actions = [an_action]  # E: List item 0 has incompatible type "Callable[[None], None]"; expected "Union[Callable[[ModelAdmin[Any], HttpRequest, QuerySet[Any]], None], str]"