Fix overriding AppConfig.default_auto_field with string value (#1596)

Co-authored-by: Adam Johnson <me@adamj.eu>

Author: GabDug

django-stubs/apps/config.pyi

@@ -3,7 +3,7 @@ from collections.abc import Iterator
 
 from django.apps.registry import Apps
 from django.db.models.base import Model
-from django.utils.functional import _StrOrPromise, cached_property
+from django.utils.functional import _Getter, _StrOrPromise
 
 APPS_MODULE_NAME: str
 MODELS_MODULE_NAME: str
@@ -16,10 +16,11 @@ class AppConfig:
     verbose_name: _StrOrPromise
     path: str
     models_module: str | None
+    # Default auto_field is a cached_property on the base, but is usually subclassed as a str
+    # If not subclassing with a str, a type ignore[override] is needed
     models: dict[str, type[Model]]
+    default_auto_field: str | _Getter[str]
     def __init__(self, app_name: str, app_module: types.ModuleType | None) -> None: ...
-    @cached_property
-    def default_auto_field(self) -> str: ...
     @classmethod
     def create(cls, entry: str) -> AppConfig: ...
     def get_model(self, model_name: str, require_ready: bool = ...) -> type[Model]: ...

tests/typecheck/apps/test_config.yml

@@ -0,0 +1,29 @@
+-   case: test_appconfig_can_be_str
+    main: |
+      from django.apps.config import AppConfig
+      from django.utils.functional import cached_property
+
+      class FooConfig(AppConfig):
+          name = "foo"
+          default_auto_field = "django.db.models.BigAutoField"
+
+      class BarConfig(AppConfig):
+          name = "foo"
+          @property
+          def default_auto_field(self) -> str: # type: ignore[override]
+              return "django.db.models.BigAutoField"
+
+      class BazConfig(AppConfig):
+          name = "foo"
+          @cached_property
+          def default_auto_field(self) -> str: # type: ignore[override]
+              return "django.db.models.BigAutoField"
+
+      class FooBarConfig(AppConfig):
+          name = "foo"
+          default_auto_field = cached_property(lambda self: "django.db.models.BigAutoField")
+
+      reveal_type(FooConfig.default_auto_field)  # N: Revealed type is "builtins.str"
+      reveal_type(BarConfig("bar", None).default_auto_field)  # N: Revealed type is "builtins.str"
+      reveal_type(BazConfig("baz", None).default_auto_field)  # N: Revealed type is "builtins.str"
+      reveal_type(FooBarConfig("baz", None).default_auto_field)  # N: Revealed type is "builtins.str"