Improve system check registry hints

django-stubs/core/checks/registry.pyi

@@ -1,9 +1,9 @@
-from collections.abc import Callable, Sequence
-from typing import Any, Protocol, TypeVar
+from collections.abc import Callable, Iterable, Sequence
+from typing import Any, Protocol, TypeVar, overload
 
 from django.apps.config import AppConfig
+from django.apps.registry import Apps
 from django.core.checks.messages import CheckMessage
-from typing_extensions import TypeAlias
 
 class Tags:
     admin: str
@@ -19,7 +19,10 @@ class Tags:
     translation: str
     urls: str
 
-_CheckCallable: TypeAlias = Callable[..., Sequence[CheckMessage]]
+class _CheckCallable(Protocol):
+    def __call__(
+        self, *, app_configs: Apps, databases: Sequence[str] | None, **kwargs: Any
+    ) -> Iterable[CheckMessage]: ...
 
 _C = TypeVar("_C", bound=_CheckCallable)
 
@@ -31,21 +34,22 @@ class CheckRegistry:
     registered_checks: set[_ProcessedCheckCallable]
     deployment_checks: set[_ProcessedCheckCallable]
     def __init__(self) -> None: ...
-    def register(
-        self, check: _CheckCallable | str | None = ..., *tags: str, **kwargs: Any
-    ) -> Callable[[_CheckCallable], _ProcessedCheckCallable] | _ProcessedCheckCallable: ...
+    @overload
+    def register(self, __check: _C) -> _ProcessedCheckCallable[_C]: ...
+    @overload
+    def register(self, *tags: str, **kwargs: Any) -> Callable[[_C], _ProcessedCheckCallable[_C]]: ...
     def run_checks(
         self,
         app_configs: Sequence[AppConfig] | None = ...,
         tags: Sequence[str] | None = ...,
         include_deployment_checks: bool = ...,
-        databases: Any | None = ...,
+        databases: Sequence[str] | None = ...,
     ) -> list[CheckMessage]: ...
     def tag_exists(self, tag: str, include_deployment_checks: bool = ...) -> bool: ...
     def tags_available(self, deployment_checks: bool = ...) -> set[str]: ...
     def get_checks(self, include_deployment_checks: bool = ...) -> list[_ProcessedCheckCallable]: ...
 
-registry: CheckRegistry
-register: Any
-run_checks: Any
-tag_exists: Any
+registry: CheckRegistry = ...
+register = registry.register
+run_checks = registry.run_checks
+tag_exists = registry.tag_exists

tests/typecheck/core/test_checks.yml

@@ -0,0 +1,24 @@
+- case: test_checks_register
+  main: |
+    from typing import Any, Sequence, Optional
+
+    from django.core.checks import register, Warning, CheckMessage
+    from django.apps.registry import Apps
+
+
+    @register("foo", deploy=True)
+    def check_foo(app_configs: Apps, databases: Optional[Sequence[str]], **kwargs: Any) -> list[Warning]:
+        if databases and 'databass' in databases:
+            return [Warning("Naughty list")]
+        return []
+
+    reveal_type(check_foo)  # N: Revealed type is "django.core.checks.registry._ProcessedCheckCallable[def (app_configs: django.apps.registry.Apps, databases: Union[typing.Sequence[builtins.str], None], **kwargs: Any) -> builtins.list[django.core.checks.messages.Warning]]"
+    reveal_type(check_foo.tags)  # N: Revealed type is "typing.Sequence[builtins.str]"
+
+    @register
+    def check_bar(**kwargs: Any) -> Sequence[CheckMessage]: ...
+
+    reveal_type(check_bar)  # N: Revealed type is "django.core.checks.registry._ProcessedCheckCallable[def (**kwargs: Any) -> typing.Sequence[django.core.checks.messages.CheckMessage]]"
+
+    @register()  # E: Value of type variable "_C" of function cannot be "Callable[[int], Sequence[CheckMessage]]"
+    def wrong_args(bla: int) -> Sequence[CheckMessage]: ...