decorator: Strengthen decorator types using ParamSpec.

Signed-off-by: Zixuan James Li <359101898@qq.com>

zerver/decorator.py

@@ -24,6 +24,7 @@ from django.utils.translation import gettext as _
 from django.views.decorators.csrf import csrf_exempt
 from django_otp import user_has_device
 from two_factor.utils import default_device
+from typing_extensions import ParamSpec
 
 from zerver.lib.cache import cache_with_key
 from zerver.lib.exceptions import (
@@ -67,7 +68,8 @@ webhook_logger = logging.getLogger("zulip.zerver.webhooks")
 webhook_unsupported_events_logger = logging.getLogger("zulip.zerver.webhooks.unsupported")
 webhook_anomalous_payloads_logger = logging.getLogger("zulip.zerver.webhooks.anomalous")
 
-FuncT = TypeVar("FuncT", bound=Callable[..., object])
+ParamT = ParamSpec("ParamT")
+ReturnT = TypeVar("ReturnT")
 
 
 def update_user_activity(
@@ -847,20 +849,22 @@ def to_utc_datetime(var_name: str, timestamp: str) -> datetime.datetime:
     return timestamp_to_datetime(float(timestamp))
 
 
-def statsd_increment(counter: str, val: int = 1) -> Callable[[FuncT], FuncT]:
+def statsd_increment(
+    counter: str, val: int = 1
+) -> Callable[[Callable[ParamT, ReturnT]], Callable[ParamT, ReturnT]]:
     """Increments a statsd counter on completion of the
     decorated function.
 
     Pass the name of the counter to this decorator-returning function."""
 
-    def wrapper(func: FuncT) -> FuncT:
+    def wrapper(func: Callable[ParamT, ReturnT]) -> Callable[ParamT, ReturnT]:
         @wraps(func)
-        def wrapped_func(*args: object, **kwargs: object) -> object:
+        def wrapped_func(*args: ParamT.args, **kwargs: ParamT.kwargs) -> ReturnT:
             ret = func(*args, **kwargs)
             statsd.incr(counter, val)
             return ret
 
-        return cast(FuncT, wrapped_func)  # https://github.com/python/mypy/issues/1927
+        return wrapped_func
 
     return wrapper