Pyright does not handle NoReturn in async await

[kumaraditya303]

Note: if you are reporting a wrong signature of a function or a class in the standard library, then the typeshed tracker is better suited for this report: https://github.com/python/typeshed/issues.

Describe the bug
Pyright does not handle NoReturn in async await

Expected behavior
No error.

Screenshots or Code
If applicable, add screenshots or the text of the code (surrounded by triple back ticks) to help explain your problem.

# pyright: strict
import asyncio
from typing import NoReturn


async def func() -> NoReturn:
    while True:
        await asyncio.sleep(1)
        print("Hello World!")


async def main() -> NoReturn:
    await func()
    # <--- This will never execute 


asyncio.run(main())

VS Code extension or command-line
Are you running pyright as a VS Code extension or a command-line tool? Which version? You can find the version of the VS Code extension by clicking on the Pyright icon in the extensions panel.

pyright 1.1.189

[kumaraditya303]

Same happens with generators too:

# pyright: strict
from typing import Generator, NoReturn


def func() -> Generator[int, None, NoReturn]:
    c = 0
    while True:
        c += 1
        yield c


def main() -> NoReturn:
    for i in func():
        print(i)
    # <--- This will never execute 

main()

[erictraut]

I've fixed the issue with async functions.

I'm not convinced the second one is valid though. The NoReturn type is not supposed to be used as a type argument. Mypy generates the same error in this case. I think you'll need to use a workaround in the case of a generator.

[kumaraditya303]

I'm not convinced the second one is valid though. The NoReturn type is not supposed to be used as a type argument. Mypy generates the same error in this case. I think you'll need to use a workaround in the case of a generator.

If that's the case then why in async function the type can be () -> Coroutine[Any, Any, NoReturn] but in generator it cannot be () -> Generator[int, None, NoReturn] ?

[erictraut]

NoReturn should not be used as a type argument, so Coroutine[Any, Any, NoReturn] is technically not permitted, but it is legal to use async func() -> NoReturn.

[kumaraditya303]

It still looks wrong to me that NoReturn cannot be used in case of generators, I have started a discussion on it in typing repo
python/typing#960

[erictraut]

This is included in pyright 1.1.190, which I just published. It will also be included in the next release of pylance.

[BRIZINGR007]

Hi Guys , You can create a asyncio.create_task and await that task. With this the Pyright does not throw <"NoReturn" is not awaitable>.

response = asyncio.create_task( awaitable ).
response = await response

Below is an example I solved for aioboto3 for sqs polling :

response = asyncio.create_task( async_sqs_client.receive_message( QueueUrl=self.queue_url, MaxNumberOfMessages=batch_size_of_messages, WaitTimeSeconds=max_polling_duration ) )
response = await response