async def test_contextmanager(self):
async def acquire():
async with semaphore:
assert semaphore.value in (0, 1)
semaphore = Semaphore(2)
async with create_task_group() as tg:
tg.start_soon(acquire, name='task 1')
tg.start_soon(acquire, name='task 2')
assert semaphore.value == 2
async def test_manual_acquire(self):
async def acquire():
await semaphore.acquire()
try:
assert semaphore.value in (0, 1)
finally:
semaphore.release()
semaphore = Semaphore(2)
async with create_task_group() as tg:
tg.start_soon(acquire, name='task 1')
tg.start_soon(acquire, name='task 2')
assert semaphore.value == 2
async def test_asyncio_deadlock(self) -> None:
"""Regression test for #398."""
semaphore = Semaphore(1)
async def acquire() -> None:
async with semaphore:
await asyncio.sleep(0)
loop = asyncio.get_event_loop()
task1 = loop.create_task(acquire())
task2 = loop.create_task(acquire())
await asyncio.sleep(0)
task1.cancel()
await asyncio.wait_for(task2, 1)
async def test_acquire_cancel(self):
async def task():
nonlocal local_scope, acquired
with CancelScope() as local_scope:
async with semaphore:
acquired = True
local_scope = acquired = None
semaphore = Semaphore(1)
async with create_task_group() as tg:
async with semaphore:
tg.start_soon(task)
await wait_all_tasks_blocked()
local_scope.cancel()
assert not acquired
async def test_acquire_race(self):
"""
Test against a race condition: when a task waiting on acquire() is rescheduled but another
task snatches the last available slot, the task should not raise WouldBlock.
"""
semaphore = Semaphore(1)
async with create_task_group() as tg:
semaphore.acquire_nowait()
tg.start_soon(semaphore.acquire)
await wait_all_tasks_blocked()
semaphore.release()
pytest.raises(WouldBlock, semaphore.acquire_nowait)
async def test_statistics(self):
async def waiter():
async with semaphore:
pass
semaphore = Semaphore(1)
async with create_task_group() as tg:
assert semaphore.statistics().tasks_waiting == 0
async with semaphore:
assert semaphore.statistics().tasks_waiting == 0
for i in range(1, 3):
tg.start_soon(waiter)
await wait_all_tasks_blocked()
assert semaphore.statistics().tasks_waiting == i
assert semaphore.statistics().tasks_waiting == 0
async def test_cancel_during_acquire(self, release_first: bool) -> None:
acquired = False
async def task(*, task_status: TaskStatus) -> None:
nonlocal acquired
task_status.started()
async with semaphore:
acquired = True
semaphore = Semaphore(1)
async with create_task_group() as tg:
await semaphore.acquire()
await tg.start(task)
tg.cancel_scope.cancel()
with CancelScope(shield=True):
if release_first:
semaphore.release()
await wait_all_tasks_blocked()
else:
await wait_all_tasks_blocked()
semaphore.release()
assert not acquired
assert semaphore.value == 1
async def test_max_value_exceeded(self):
semaphore = Semaphore(1, max_value=2)
semaphore.release()
pytest.raises(ValueError, semaphore.release)
async def test_max_value(self, max_value):
semaphore = Semaphore(0, max_value=max_value)
assert semaphore.max_value == max_value
async def test_acquire_nowait(self):
semaphore = Semaphore(1)
semaphore.acquire_nowait()
assert semaphore.value == 0
pytest.raises(WouldBlock, semaphore.acquire_nowait)
async def test_semaphore_release(self) -> None:
semaphore = Semaphore(1)
semaphore.acquire_nowait()
with pytest.deprecated_call():
await semaphore.release()
async def test_max_value(self, max_value: Optional[int]) -> None:
semaphore = Semaphore(0, max_value=max_value)
assert semaphore.max_value == max_value
