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decorators cannot get type hints for async function return values #1283
Description
I use a decorator to get the return value type of a synchronous function, it's ok.
this code:
import asyncio
from functools import wraps
from typing import Any, Awaitable, Callable, TypeVar, ParamSpec, Coroutine
T = TypeVar("T") # the callable/awaitable return type
P = ParamSpec("P") # the callable parameters
def sync_dec(message: Any) -> Callable[[Callable[P, T]], Callable[P, T]]:
def wrapper(f: Callable[P, T]) -> Callable[P, T]:
@wraps(f)
def inner(*args: Any, **kwargs: Any) -> T:
print(message)
return f(*args, **kwargs)
return inner
return wrapper
@sync_dec("hello")
def f(x: int, y: int) -> int:
return x + y
f() # error: missing positional argument "x" and "y" in call to "f"
f(1, 2) # ok
but，I can't get the return value type hint of an async function using a decorator.
this code:
def async_dec(message: Any):
def wrapper(f: Callable[P, Awaitable[T]]) -> Callable[P, Awaitable[T]]:
async def inner(*args: Any, **kwargs: Any) -> T:
print(message)
return await f(*args, **kwargs)
return inner
return wrapper
@async_dec("hello")
async def f3(a: int, b: int) -> int:
return a + b
async def run():
await f3() # missing positional argument "x" and "y" in call to "f3"
r = await f3(1, 2)
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