asyncio.create_task doesn't accept coroutine like objects
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topic: asyncio
- Dominant language
- Python
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Description
The following code fails to typecheck with latest mypy but works just fine at runtime.
from typing import Any
import asyncio
class MyCoro:
def __init__(self):
async def coro() -> None:
print("coro works!")
self.coro = coro()
def send(self, value: Any) -> None:
return self.coro.send(value)
def throw(self, exc: BaseException) -> None:
return self.coro.throw(exc)
def close(self) -> None:
return self.coro.close()
def __await__(self) -> Any:
return self.coro.__await__()
async def main() -> None:
coro = MyCoro()
await asyncio.create_task(coro)
asyncio.run(main())
Error:
cpython on isolate-decimal [?] via 🐍 v3.11.2
❯ mypy main.py
main.py:25: error: Argument 1 to "create_task" has incompatible type "MyCoro"; expected "Union[Generator[Any, None, <nothing>], Coroutine[Any, Any, <nothing>]]" [arg-type]
Found 1 error in 1 file (checked 1 source file)
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the example with mypy and inspect the typeshed stub for asyncio.create_task. Compare its accepted argument types with the runtime behavior shown for MyCoro. Done means the example typechecks without weakening unrelated asyncio typing behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100