Improve pyre typing

Summary: Small pyre improvement to later library.

Reviewed By: fried, zsol

Differential Revision: D62593644

fbshipit-source-id: ed2836c5e11253366fb0e5eb20b5f1b5db31ffcd

Author: Jakub Grzmiel

later/task.py

@@ -38,6 +38,7 @@
     NewType,
     Optional,
     overload,
+    ParamSpec,
     Protocol,
     Sequence,
     Tuple,
@@ -53,6 +54,7 @@
 FixerType = Callable[[asyncio.Task], Union[asyncio.Task, Awaitable[asyncio.Task]]]
 logger: logging.Logger = logging.getLogger(__name__)
 T = TypeVar("T")
+TParams = ParamSpec("TParams")
 
 __all__: Sequence[str] = [
     "Watcher",
@@ -125,15 +127,15 @@ async def cancel(fut: asyncio.Future) -> None:
 
 
 def as_task(
-    func: Callable[..., Coroutine[object, object, T]]
-) -> Callable[..., asyncio.Task[T]]:
+    func: Callable[TParams, Coroutine[object, object, T]]
+) -> Callable[TParams, asyncio.Task[T]]:
     """
     Decorate a function, So that when called it is wrapped in a task
     on the running loop.
     """
 
     @wraps(func)
-    def create_task(*args: Any, **kws: Mapping[str, Any]) -> asyncio.Task[T]:
+    def create_task(*args: TParams.args, **kws: TParams.kwargs) -> asyncio.Task[T]:
         loop = asyncio.get_running_loop()
         return loop.create_task(func(*args, **kws))
 
@@ -161,7 +163,7 @@ class Watcher:
     _cancel_timeout: float
     _preexit_callbacks: List[Callable[[], None]]
     _shielded_tasks: Dict[asyncio.Task, asyncio.Future]
-    # pyre-fixme[13]: Attribute `loop` is never initialized.
+    # pyre-ignore[13]: loop is initialized in __aenter__
     loop: asyncio.AbstractEventLoop
     running: bool
     done_ok: bool
@@ -424,7 +426,7 @@ async def _handle_cancel(self) -> None:
             )
 
 
-CacheKey = NewType("CacheKey", Sequence[Hashable])
+CacheKey = NewType("CacheKey", tuple[Hashable, ...])
 ArgID = Union[int, str]
 
 
@@ -457,11 +459,9 @@ def _build_key(
     Allow for not including certain fields from args or kwargs
     """
     if not ignored_args:
-        # pyre-fixme[45]: Cannot instantiate abstract class `CacheKey`.
         return CacheKey((args, tuple(sorted(kwargs.items()))))
 
     # If we do want to ignore something then do so
-    # pyre-fixme[45]: Cannot instantiate abstract class `CacheKey`.
     return CacheKey(
         (
             tuple((value for idx, value in enumerate(args) if idx not in ignored_args)),
@@ -474,37 +474,40 @@ def _build_key(
 
 class AsyncCallable(Protocol):
     def __call__(
-        self, fn: Callable[..., Coroutine[object, object, T]]
-    ) -> Callable[..., Coroutine[object, object, T]]:  # pragma: nocover
+        self, fn: Callable[TParams, Coroutine[object, object, T]]
+    ) -> Callable[TParams, Coroutine[object, object, T]]:  # pragma: nocover
         ...
 
 
-FuncType = Callable[..., Coroutine[object, object, T]]
-
-
-@overload  # noqa: 811
+@overload
 def herd(
-    fn: FuncType[T], *, ignored_args: Optional[AbstractSet[ArgID]] = None
-) -> FuncType[T]:  # pragma: nocover
+    fn: Callable[TParams, Coroutine[object, object, T]],
+    *,
+    ignored_args: Optional[AbstractSet[ArgID]] = None,
+) -> Callable[TParams, Coroutine[object, object, T]]:  # pragma: nocover
     ...
 
 
-@overload  # noqa: 811
+@overload
 def herd(
-    fn: Optional[AsyncCallable] = None,
+    fn: None = None,
     *,
     ignored_args: Optional[AbstractSet[ArgID]] = None,
 ) -> AsyncCallable:  # pragma: nocover
     ...
 
 
-# pyre-ignore[3]: Defining the return type is pointless here
 def herd(
-    # pyre-ignore[2]: This is fine, we don't need types the overloads cover it
-    fn=None,
+    fn: Callable[TParams, Coroutine[object, object, T]] | None = None,
     *,
     ignored_args: Optional[AbstractSet[ArgID]] = None,
-):  # noqa: 811
+) -> (
+    Callable[TParams, Coroutine[object, object, T]]
+    | Callable[
+        [Callable[TParams, Coroutine[object, object, T]]],
+        Callable[TParams, Coroutine[object, object, T]],
+    ]
+):
     """
     Provide a simple thundering herd protection as a decorator.
     if requests comes in while and existing request with those same args is pending,
@@ -518,11 +521,13 @@ def herd(
     Each member of the herd is "shielded" from cancellation effecting other herd members
     """
 
-    def decorator(fn: FuncType[T]) -> T:
+    def decorator(
+        fn: Callable[TParams, Coroutine[object, object, T]]
+    ) -> Callable[TParams, Coroutine[object, object, T]]:
         local: threading.local = threading.local()
 
         @functools.wraps(fn)
-        async def wrapped(*args: Any, **kwargs: Any) -> T:
+        async def wrapped(*args: TParams.args, **kwargs: TParams.kwargs) -> T:
             pending = cast(Dict[CacheKey, _CountTask], _get_local(local, "pending"))
             request = _build_key(tuple(args), kwargs, ignored_args)
             count_task = pending.setdefault(request, _CountTask())
@@ -548,7 +553,6 @@ async def wrapped(*args: Any, **kwargs: Any) -> T:
         return wrapped
 
     if fn and callable(fn):
-        # pyre-fixme[6]: For 1st param expected `F` but got `(...) -> object`.
         return decorator(fn)
 
     return decorator