Should I report and/or submit PRs for type hint issues?

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1

Hi! I was recently running some sample code in the async-tasks section of the docs. I noticed that the following example does not play nicely with VS Code / pyright. Given the current state of type hints in the project, I wasn’t sure if I should spam the repo with type related issues / PRs. Is this something I should report and/or submit a PR for?

import asyncio

from prefect import task, flow

@task
async def print_values(values):
    for value in values:
        await asyncio.sleep(1) # yield
        print(value, end=" ")

@flow
async def async_flow():
    await print_values([1, 2])  # runs immediately
    coros = [print_values("abcd"), print_values("6789")]

    # asynchronously gather the tasks
    await asyncio.gather(*coros)

asyncio.run(async_flow())  # ERROR: Awaitable[None] is incompatible with Coroutine[Any, Any, _T@run]

It appears that the issue is coming from one of the type overloads of Flow.__call__:

    @overload
    def __call__(
        self: "Flow[P, Coroutine[Any, Any, T]]", *args: P.args, **kwargs: P.kwargs
    ) -> Awaitable[T]:
        ...

Since the generic Flow type indicates that we are wrapping a Coroutine, which derives from an Awaitable, I thought it would be useful to avoid a potential Liskov substitution violation and return a Coroutine[Any, Any, T].

2

Thanks for the post @cswartzvi - if I go and install Pyright for my IDE then I can reproduce this type warning.

I would suggest you create a github issue to discuss this and see whether there would be additional ramifications associated with this type change.