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Fixed inability to start tasks from async_generator_asend objects on asyncio #675

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Fixed inability to start tasks from async_generator_asend objects on asyncio #675

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ac34de0
Fixed inability to start tasks from async_generator_asend objects on …
agronholm Jan 20, 2024
c9307ee
Merge branch 'master' into allow-asyncgen-asend-objects
agronholm Jan 20, 2024
19b4e58
Merge branch 'master' into allow-asyncgen-asend-objects
agronholm Jan 31, 2024
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1 change: 1 addition & 0 deletions docs/versionhistory.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
- Fixed ``Process.stdin.aclose()``, ``Process.stdout.aclose()``, and
``Process.stderr.aclose()`` not including a checkpoint on asyncio (PR by Ganden
Schaffner)
- Fixed inability to start tasks from ``async_generator_asend`` objects on asyncio

**4.2.0**

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6 changes: 2 additions & 4 deletions src/anyio/_backends/_asyncio.py
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Expand Up @@ -18,7 +18,7 @@
)
from asyncio.base_events import _run_until_complete_cb # type: ignore[attr-defined]
from collections import OrderedDict, deque
from collections.abc import AsyncIterator, Generator, Iterable
from collections.abc import AsyncIterator, Coroutine, Generator, Iterable
from concurrent.futures import Future
from contextlib import suppress
from contextvars import Context, copy_context
Expand All @@ -28,7 +28,6 @@
CORO_RUNNING,
CORO_SUSPENDED,
getcoroutinestate,
iscoroutine,
)
from io import IOBase
from os import PathLike
Expand All @@ -45,7 +44,6 @@
Callable,
Collection,
ContextManager,
Coroutine,
Mapping,
Optional,
Sequence,
Expand Down Expand Up @@ -741,7 +739,7 @@ def task_done(_task: asyncio.Task) -> None:
parent_id = id(self.cancel_scope._host_task)

coro = func(*args, **kwargs)
if not iscoroutine(coro):
if not isinstance(coro, Coroutine):
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the above comment is about async_generator_asend specifically, but in general it seems buggy to replace inspect.iscoroutine here with either (a) abc.Coroutine.__instancecheck__ or (b) asyncio.iscoroutine.

the problem is that anything that AnyIO allows past this check needs to support inspect.getcoroutinestate (because of _task_started), but:

  • (a) and (b) would allow through coroutines/coroutine-likes that don't support getcoroutinestate, such as types that implement the abc.Coroutine interface but are not inspectable (e.g. async_generator_asend) and types that a user or a third-party library calls abc.Coroutine.register on.

  • (b) would also allow through "coroutine-likes" that aren't even coroutine-like, such as every generator on Python < 3.12.

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Thank you for the in-depth analysis. In this light, wrapping the async_generator_asend object in a coroutine might be less of a hassle. I need to consider my options here.

prefix = f"{func.__module__}." if hasattr(func, "__module__") else ""
raise TypeError(
f"Expected {prefix}{func.__qualname__}() to return a coroutine, but "
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16 changes: 16 additions & 0 deletions tests/test_taskgroups.py
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Expand Up @@ -1336,6 +1336,22 @@ async def wait_cancel() -> None:
await cancelled.wait()


async def test_start_soon_from_asend() -> None:
started = False

async def genfunc() -> AsyncGenerator[None, None]:
nonlocal started
started = True
yield

generator = genfunc()
async with anyio.create_task_group() as task_group:
task_group.start_soon(generator.asend, None)

assert started
await generator.aclose()


class TestTaskStatusTyping:
"""
These tests do not do anything at run time, but since the test suite is also checked
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