More gather (#6)

* More gather

* Fix tests for a CPython bug

* Remove unused import

README.md

@@ -48,7 +48,8 @@ async def my_handler():
  # res_1 and res_2 may be instances of exceptions.
 ```
 
-The differences to `asyncio.gather` are:
+The differences to `asyncio.gather()` are:
+- If a child task fails other unfinished tasks will be cancelled, just like in a TaskGroup.
 - `quattro.gather()` only accepts coroutines and not futures and generators, just like a TaskGroup.
 - When `return_exceptions` is false (the default), an exception in a child task will cause an ExceptionGroup to bubble out of the top-level `gather()` call, just like in a TaskGroup.
 - Results are returned as a tuple, not a list.

src/quattro/_gather.py

@@ -194,6 +194,8 @@ async def gather( # type: ignore[misc]
 
  Notable differences are:
 
+ * If a child task fails other unfinished tasks will be cancelled, just like
+ in a TaskGroup.
  * `quattro.gather` only accepts coroutines and not futures and
  generators, just like a TaskGroup.
  * When `return_exceptions` is false (the default), an exception in a child task
@@ -202,6 +204,8 @@ async def gather( # type: ignore[misc]
  * Results are returned as a tuple, not a list.
 
  (See https://docs.python.org/3/library/asyncio-task.html#asyncio.gather)
+
+ .. versionadded:: 23.1.0
  """
  if not coros:
  return ()

tests/test_gather.py

@@ -1,34 +1,39 @@
-from asyncio import CancelledError, sleep
+from asyncio import CancelledError, current_task, get_running_loop, sleep
+from asyncio import gather as asyncio_gather
 
-from pytest import raises
+from pytest import mark, raises
 
-from quattro import gather, move_on_after
+from quattro import gather
 from quattro.taskgroup import ExceptionGroup
 
 
-async def test_empty():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_empty(gather):
  """An empty gather works."""
- assert await gather() == ()
+ # asyncio gather returns a list
+ assert tuple(await gather()) == ()
 
 
-async def test_simple_gather():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_simple_gather(gather):
  """Simple gather works."""
 
  async def test() -> int:
  await sleep(0.01)
  return 1
 
- assert await gather(test(), test()) == (1, 1)
+ assert tuple(await gather(test(), test())) == (1, 1)
 
 
-async def test_gather_with_error():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_gather_with_error(gather):
  """Gather works if there's an error."""
  cancelled = 0
 
  async def test() -> int:
  nonlocal cancelled
  try:
- await sleep(0.01)
+ await sleep(0.1)
  except CancelledError:
  cancelled += 1
  return 1
@@ -37,23 +42,32 @@ async def error() -> None:
  await sleep(0.005)
  raise ValueError()
 
- with raises(ExceptionGroup) as exc_info:
+ with raises((ExceptionGroup, ValueError)) as exc_info:
  await gather(test(), test(), error())
 
- assert repr(exc_info.value.exceptions[0]) == "ValueError()"
+ if gather == asyncio_gather:
+ assert isinstance(exc_info.value, ValueError)
+ # default asyncio behavior
+ assert cancelled == 0
+ else:
+ assert isinstance(exc_info.value, ExceptionGroup)
+ assert repr(exc_info.value.exceptions[0]) == "ValueError()"
+ assert cancelled == 2
 
 
-async def test_simple_gather_exceptions():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_simple_gather_exceptions(gather):
  """Simple gather works when collecting exceptions."""
 
  async def test() -> int:
  await sleep(0.01)
  return 1
 
- assert await gather(test(), test(), return_exceptions=True) == (1, 1)
+ assert tuple(await gather(test(), test(), return_exceptions=True)) == (1, 1)
 
 
-async def test_with_error_return_excs():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_with_error_return_excs(gather):
  """Gather works if there's an error and exceptions are returned."""
 
  async def test() -> int:
@@ -68,10 +82,11 @@ async def error() -> None:
 
  res = await gather(test(), test(), error(), return_exceptions=True)
 
- assert res == (1, 1, err)
+ assert tuple(res) == (1, 1, err)
 
 
-async def test_parent_cancelled():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_parent_cancelled(gather):
  """When the parent is cancelled, the children are also cancelled."""
  cancelled = 0
 
@@ -86,14 +101,20 @@ async def test() -> int:
 
  res = None
 
- with move_on_after(0.001):
+ # We cannot use `move_on` here since asyncio.gather doesn't
+ # work with it on some versions of 3.9 and 3.10.
+ current = current_task()
+ get_running_loop().call_later(0.001, lambda: current.cancel())
+
+ with raises(CancelledError):
  res = await gather(test(), test())
 
  assert res is None
  assert cancelled == 2
 
 
-async def test_parent_cancelled_return_excs():
+@mark.parametrize("gather", [gather, asyncio_gather])
+async def test_parent_cancelled_return_excs(gather):
  """When the parent is cancelled, the children are also cancelled."""
  cancelled = 0
 
@@ -108,7 +129,13 @@ async def test() -> int:
 
  res = None
 
- with move_on_after(0.001):
+ # We cannot use
+ # `move_on` here since asyncio.gather doesn't
+ # work with it on some versions of 3.9 and 3.10.
+ current = current_task()
+ get_running_loop().call_later(0.001, lambda: current.cancel())
+
+ with raises(CancelledError):
  res = await gather(test(), test(), return_exceptions=True)
 
  assert res is None