import asyncio
import unittest
import time
from test import support
def tearDownModule():
asyncio.set_event_loop_policy(None)
# The following value can be used as a very small timeout:
# it passes check "timeout > 0", but has almost
# no effect on the test performance
_EPSILON = 0.0001
class SlowTask:
""" Task will run for this defined time, ignoring cancel requests """
TASK_TIMEOUT = 0.2
def __init__(self):
self.exited = False
async def run(self):
exitat = time.monotonic() + self.TASK_TIMEOUT
while True:
tosleep = exitat - time.monotonic()
if tosleep <= 0:
break
try:
await asyncio.sleep(tosleep)
except asyncio.CancelledError:
pass
self.exited = True
class AsyncioWaitForTest(unittest.IsolatedAsyncioTestCase):
async def test_asyncio_wait_for_cancelled(self):
t = SlowTask()
waitfortask = asyncio.create_task(
asyncio.wait_for(t.run(), t.TASK_TIMEOUT * 2))
await asyncio.sleep(0)
waitfortask.cancel()
await asyncio.wait({waitfortask})
self.assertTrue(t.exited)
async def test_asyncio_wait_for_timeout(self):
t = SlowTask()
try:
await asyncio.wait_for(t.run(), t.TASK_TIMEOUT / 2)
except asyncio.TimeoutError:
pass
self.assertTrue(t.exited)
async def test_wait_for_timeout_less_then_0_or_0_future_done(self):
loop = asyncio.get_running_loop()
fut = loop.create_future()
fut.set_result('done')
ret = await asyncio.wait_for(fut, 0)
self.assertEqual(ret, 'done')
self.assertTrue(fut.done())
async def test_wait_for_timeout_less_then_0_or_0_coroutine_do_not_started(self):
foo_started = False
async def foo():
nonlocal foo_started
foo_started = True
with self.assertRaises(asyncio.TimeoutError):
await asyncio.wait_for(foo(), 0)
self.assertEqual(foo_started, False)
async def test_wait_for_timeout_less_then_0_or_0(self):
loop = asyncio.get_running_loop()
for timeout in [0, -1]:
with self.subTest(timeout=timeout):
foo_running = None
started = loop.create_future()
async def foo():
nonlocal foo_running
foo_running = True
started.set_result(None)
try:
await asyncio.sleep(10)
finally:
foo_running = False
return 'done'
fut = asyncio.create_task(foo())
await started
with self.assertRaises(asyncio.TimeoutError):
await asyncio.wait_for(fut, timeout)
self.assertTrue(fut.done())
# it should have been cancelled due to the timeout
self.assertTrue(fut.cancelled())
self.assertEqual(foo_running, False)
async def test_wait_for(self):
foo_running = None
async def foo():
nonlocal foo_running
foo_running = True
try:
await asyncio.sleep(support.LONG_TIMEOUT)
finally:
foo_running = False
return 'done'
fut = asyncio.create_task(foo())
with self.assertRaises(asyncio.TimeoutError):
await asyncio.wait_for(fut, 0.1)
self.assertTrue(fut.done())
# it should have been cancelled due to the timeout
self.assertTrue(fut.cancelled())
self.assertEqual(foo_running, False)
async def test_wait_for_blocking(self):
async def coro():
return 'done'
res = await asyncio.wait_for(coro(), timeout=None)
self.assertEqual(res, 'done')
async def test_wait_for_race_condition(self):
loop = asyncio.get_running_loop()
fut = loop.create_future()
task = asyncio.wait_for(fut, timeout=0.2)
loop.call_soon(fut.set_result, "ok")
res = await task
self.assertEqual(res, "ok")
async def test_wait_for_cancellation_race_condition(self):
async def inner():
with self.assertRaises(asyncio.CancelledError):
await asyncio.sleep(1)
return 1
result = await asyncio.wait_for(inner(), timeout=.01)
self.assertEqual(result, 1)
async def test_wait_for_waits_for_task_cancellation(self):
task_done = False
async def inner():
nonlocal task_done
try:
await asyncio.sleep(10)
except asyncio.CancelledError:
await asyncio.sleep(_EPSILON)
raise
finally:
task_done = True
inner_task = asyncio.create_task(inner())
with self.assertRaises(asyncio.TimeoutError) as cm:
await asyncio.wait_for(inner_task, timeout=_EPSILON)
self.assertTrue(task_done)
chained = cm.exception.__context__
self.assertEqual(type(chained), asyncio.CancelledError)
async def test_wait_for_waits_for_task_cancellation_w_timeout_0(self):
task_done = False
async def foo():
async def inner():
nonlocal task_done
try:
await asyncio.sleep(10)
except asyncio.CancelledError:
await asyncio.sleep(_EPSILON)
raise
finally:
task_done = True
inner_task = asyncio.create_task(inner())
await asyncio.sleep(_EPSILON)
await asyncio.wait_for(inner_task, timeout=0)
with self.assertRaises(asyncio.TimeoutError) as cm:
await foo()
self.assertTrue(task_done)
chained = cm.exception.__context__
self.assertEqual(type(chained), asyncio.CancelledError)
async def test_wait_for_reraises_exception_during_cancellation(self):
class FooException(Exception):
pass
async def foo():
async def inner():
try:
await asyncio.sleep(0.2)
finally:
raise FooException
inner_task = asyncio.create_task(inner())
await asyncio.wait_for(inner_task, timeout=_EPSILON)
with self.assertRaises(FooException):
await foo()
async def _test_cancel_wait_for(self, timeout):
loop = asyncio.get_running_loop()
async def blocking_coroutine():
fut = loop.create_future()
# Block: fut result is never set
await fut
task = asyncio.create_task(blocking_coroutine())
wait = asyncio.create_task(asyncio.wait_for(task, timeout))
loop.call_soon(wait.cancel)
with self.assertRaises(asyncio.CancelledError):
await wait
# Python issue #23219: cancelling the wait must also cancel the task
self.assertTrue(task.cancelled())
async def test_cancel_blocking_wait_for(self):
await self._test_cancel_wait_for(None)
async def test_cancel_wait_for(self):
await self._test_cancel_wait_for(60.0)
async def test_wait_for_cancel_suppressed(self):
# GH-86296: Suppressing CancelledError is discouraged
# but if a task suppresses CancelledError and returns a value,
# `wait_for` should return the value instead of raising CancelledError.
# This is the same behavior as `asyncio.timeout`.
async def return_42():
try:
await asyncio.sleep(10)
except asyncio.CancelledError:
return 42
res = await asyncio.wait_for(return_42(), timeout=0.1)
self.assertEqual(res, 42)
async def test_wait_for_issue86296(self):
# GH-86296: The task should get cancelled and not run to completion.
# inner completes in one cycle of the event loop so it
# completes before the task is cancelled.
async def inner():
return 'done'
inner_task = asyncio.create_task(inner())
reached_end = False
async def wait_for_coro():
await asyncio.wait_for(inner_task, timeout=100)
await asyncio.sleep(1)
nonlocal reached_end
reached_end = True
task = asyncio.create_task(wait_for_coro())
self.assertFalse(task.done())
# Run the task
await asyncio.sleep(0)
task.cancel()
with self.assertRaises(asyncio.CancelledError):
await task
self.assertTrue(inner_task.done())
self.assertEqual(await inner_task, 'done')
self.assertFalse(reached_end)
class WaitForShieldTests(unittest.IsolatedAsyncioTestCase):
async def test_zero_timeout(self):
# `asyncio.shield` creates a new task which wraps the passed in
# awaitable and shields it from cancellation so with timeout=0
# the task returned by `asyncio.shield` aka shielded_task gets
# cancelled immediately and the task wrapped by it is scheduled
# to run.
async def coro():
await asyncio.sleep(0.01)
return 'done'
task = asyncio.create_task(coro())
with self.assertRaises(asyncio.TimeoutError):
shielded_task = asyncio.shield(task)
await asyncio.wait_for(shielded_task, timeout=0)
# Task is running in background
self.assertFalse(task.done())
self.assertFalse(task.cancelled())
self.assertTrue(shielded_task.cancelled())
# Wait for the task to complete
await asyncio.sleep(0.1)
self.assertTrue(task.done())
async def test_none_timeout(self):
# With timeout=None the timeout is disabled so it
# runs till completion.
async def coro():
await asyncio.sleep(0.1)
return 'done'
task = asyncio.create_task(coro())
await asyncio.wait_for(asyncio.shield(task), timeout=None)
self.assertTrue(task.done())
self.assertEqual(await task, "done")
async def test_shielded_timeout(self):
# shield prevents the task from being cancelled.
async def coro():
await asyncio.sleep(0.1)
return 'done'
task = asyncio.create_task(coro())
with self.assertRaises(asyncio.TimeoutError):
await asyncio.wait_for(asyncio.shield(task), timeout=0.01)
self.assertFalse(task.done())
self.assertFalse(task.cancelled())
self.assertEqual(await task, "done")
if __name__ == '__main__':
unittest.main()
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