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Example Code

from collections.abc import AsyncGenerator
from contextlib import asynccontextmanager

from fastapi import FastAPI


@asynccontextmanager
async def lifespan(_: FastAPI) -> AsyncGenerator[None, None]:
    ...
    yield
    ...


app = FastAPI(lifespan=lifespan)

Description

I have taken the example from the docs of the lifespan async context manager - new in 0.93 - shaved it down to the bare minimum, and added typing hints.

When running this code through mypy-1.1.1 it complains about the type of the lifespan() context manager:

$ pipenv run mypy lifespan_example.py
Loading .env environment variables...
lifespan_example.py:14: error:
  Argument "lifespan" to "FastAPI" has incompatible type 
    "Callable[[FastAPI], _AsyncGeneratorContextManager[None]]";
  expected
    "Union[Callable[[Starlette], AbstractAsyncContextManager[None]], Callable[[Starlette], AbstractAsyncContextManager[Mapping[str, Any]]], None]"  [arg-type]
Found 1 error in 1 file (checked 1 source file)

I am unsure whether this is an issue with FastAPI, mypy, contextlib, or me. 🤷

Operating System

Linux

Operating System Details

Ubuntu 20.04 running in WSL2.

FastAPI Version

0.94

Python Version

3.10.8

Additional Context

No response