From 9b6ee12ffe69c8e859306b955ae32428f0b2afa2 Mon Sep 17 00:00:00 2001
From: Russ Allbery <rra@lsst.org>
Date: Tue, 4 Apr 2023 13:04:11 -0700
Subject: [PATCH] Use more accurate type for exception conversion

In the wrapper to convert exceptions to a richer exception type,
make use of the new ParamSpec feature to preserve the precise type
of the underlying method.
---
 src/rsp_restspawner/spawner.py | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/rsp_restspawner/spawner.py b/src/rsp_restspawner/spawner.py
index 8da1f07..cebdbf4 100644
--- a/src/rsp_restspawner/spawner.py
+++ b/src/rsp_restspawner/spawner.py
@@ -3,13 +3,13 @@
 from __future__ import annotations
 
 import asyncio
-from collections.abc import AsyncIterator, Awaitable, Callable
+from collections.abc import AsyncIterator, Callable, Coroutine
 from dataclasses import dataclass
 from datetime import timedelta
 from enum import Enum
 from functools import wraps
 from pathlib import Path
-from typing import Any, Optional, TypeVar, cast
+from typing import Any, Optional, ParamSpec, TypeVar
 
 from httpx import AsyncClient, HTTPError
 from httpx_sse import ServerSentEvent, aconnect_sse
@@ -23,7 +23,8 @@
     SpawnFailedError,
 )
 
-F = TypeVar("F", bound=Callable[..., Awaitable[Any]])
+P = ParamSpec("P")
+T = TypeVar("T")
 
 __all__ = [
     "LabStatus",
@@ -107,17 +108,19 @@ def to_dict(self) -> dict[str, int | str]:
         }
 
 
-def _convert_exception(f: F) -> F:
+def _convert_exception(
+    f: Callable[P, Coroutine[None, None, T]]
+) -> Callable[P, Coroutine[None, None, T]]:
     """Convert ``httpx`` exceptions to `ControllerWebError`."""
 
     @wraps(f)
-    async def wrapper(*args: Any, **kwargs: Any) -> Any:
+    async def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
         try:
             return await f(*args, **kwargs)
         except HTTPError as e:
             raise ControllerWebError.from_exception(e) from e
 
-    return cast(F, wrapper)
+    return wrapper
 
 
 class RSPRestSpawner(Spawner):