Generic ExceptionHandler type

starlette/_exception_handler.py

@@ -9,11 +9,11 @@
 from starlette.types import ASGIApp, ExceptionHandler, Message, Receive, Scope, Send
 from starlette.websockets import WebSocket
 
-ExceptionHandlers = dict[typing.Any, ExceptionHandler]
-StatusHandlers = dict[int, ExceptionHandler]
+ExceptionHandlers = dict[typing.Any, ExceptionHandler[Exception]]
+StatusHandlers = dict[int, ExceptionHandler[Exception]]
 
 
-def _lookup_exception_handler(exc_handlers: ExceptionHandlers, exc: Exception) -> ExceptionHandler | None:
+def _lookup_exception_handler(exc_handlers: ExceptionHandlers, exc: Exception) -> ExceptionHandler[Exception] | None:
     for cls in type(exc).__mro__:
         if cls in exc_handlers:
             return exc_handlers[cls]

starlette/applications.py

@@ -17,7 +17,15 @@
 from starlette.requests import Request
 from starlette.responses import Response
 from starlette.routing import BaseRoute, Router
-from starlette.types import ASGIApp, ExceptionHandler, Lifespan, Receive, Scope, Send
+from starlette.types import (
+    ASGIApp,
+    ExceptionHandler,
+    ExceptionType,
+    Lifespan,
+    Receive,
+    Scope,
+    Send,
+)
 from starlette.websockets import WebSocket
 
 AppType = typing.TypeVar("AppType", bound="Starlette")
@@ -32,7 +40,8 @@ def __init__(
         debug: bool = False,
         routes: typing.Sequence[BaseRoute] | None = None,
         middleware: typing.Sequence[Middleware] | None = None,
-        exception_handlers: typing.Mapping[typing.Any, ExceptionHandler] | None = None,
+        exception_handlers: typing.Mapping[typing.Any, typing.Callable[[typing.Any, typing.Any], typing.Any]]
+        | None = None,
         on_startup: typing.Sequence[typing.Callable[[], typing.Any]] | None = None,
         on_shutdown: typing.Sequence[typing.Callable[[], typing.Any]] | None = None,
         lifespan: Lifespan[AppType] | None = None,
@@ -132,8 +141,8 @@ def add_middleware(
 
     def add_exception_handler(
         self,
-        exc_class_or_status_code: int | type[Exception],
-        handler: ExceptionHandler,
+        exc_class_or_status_code: int | type[ExceptionType],
+        handler: ExceptionHandler[ExceptionType],
     ) -> None:  # pragma: no cover
         self.exception_handlers[exc_class_or_status_code] = handler
 

starlette/types.py

@@ -19,6 +19,11 @@
 StatefulLifespan = typing.Callable[[AppType], typing.AsyncContextManager[typing.Mapping[str, typing.Any]]]
 Lifespan = typing.Union[StatelessLifespan[AppType], StatefulLifespan[AppType]]
 
-HTTPExceptionHandler = typing.Callable[["Request", Exception], "Response | typing.Awaitable[Response]"]
-WebSocketExceptionHandler = typing.Callable[["WebSocket", Exception], typing.Awaitable[None]]
-ExceptionHandler = typing.Union[HTTPExceptionHandler, WebSocketExceptionHandler]
+ExceptionType = typing.TypeVar("ExceptionType", bound=Exception)
+
+HTTPExceptionHandler = typing.Callable[["Request", ExceptionType], "Response | typing.Awaitable[Response]"]
+WebSocketExceptionHandler = typing.Callable[["WebSocket", ExceptionType], typing.Awaitable[None]]
+ExceptionHandler = typing.Union[
+    HTTPExceptionHandler[ExceptionType],
+    WebSocketExceptionHandler[ExceptionType],
+]