Lib/test/test_asyncio/test_waitfor.py

import asyncio
import unittest
import time


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')

        t0 = loop.time()
        ret = await asyncio.wait_for(fut, 0)
        t1 = loop.time()

        self.assertEqual(ret, 'done')
        self.assertTrue(fut.done())
        self.assertLess(t1 - t0, 0.1)

    async def test_wait_for_timeout_less_then_0_or_0_coroutine_do_not_started(self):
        loop = asyncio.get_running_loop()

        foo_started = False

        async def foo():
            nonlocal foo_started
            foo_started = True

        with self.assertRaises(asyncio.TimeoutError):
            t0 = loop.time()
            await asyncio.wait_for(foo(), 0)
        t1 = loop.time()

        self.assertEqual(foo_started, False)
        self.assertLess(t1 - t0, 0.1)

    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):
                    t0 = loop.time()
                    await asyncio.wait_for(fut, timeout)
                t1 = loop.time()

                self.assertTrue(fut.done())
                # it should have been cancelled due to the timeout
                self.assertTrue(fut.cancelled())
                self.assertEqual(foo_running, False)
                self.assertLess(t1 - t0, 0.1)

    async def test_wait_for(self):
        loop = asyncio.get_running_loop()
        foo_running = None

        async def foo():
            nonlocal foo_running
            foo_running = True
            try:
                await asyncio.sleep(10)
            finally:
                foo_running = False
            return 'done'

        fut = asyncio.create_task(foo())

        with self.assertRaises(asyncio.TimeoutError):
            t0 = loop.time()
            await asyncio.wait_for(fut, 0.1)
        t1 = loop.time()
        self.assertTrue(fut.done())
        # it should have been cancelled due to the timeout
        self.assertTrue(fut.cancelled())
        self.assertLess(t1 - t0, 0.2)
        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_later(0.1, 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_wait_for_self_cancellation(self):
        async def inner():
            try:
                await asyncio.sleep(0.3)
            except asyncio.CancelledError:
                try:
                    await asyncio.sleep(0.3)
                except asyncio.CancelledError:
                    await asyncio.sleep(0.3)

            return 42

        inner_task = asyncio.create_task(inner())

        wait = asyncio.wait_for(inner_task, timeout=0.1)

        # Test that wait_for itself is properly cancellable
        # even when the initial task holds up the initial cancellation.
        task = asyncio.create_task(wait)
        await asyncio.sleep(0.2)
        task.cancel()

        with self.assertRaises(asyncio.CancelledError):
            await task

        self.assertEqual(await inner_task, 42)



if __name__ == '__main__':
    unittest.main()