diff options
Diffstat (limited to 'Lib/asyncio/tasks.py')
| -rw-r--r-- | Lib/asyncio/tasks.py | 77 |
1 files changed, 29 insertions, 48 deletions
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py index e78719de216..a2e06d5ef72 100644 --- a/Lib/asyncio/tasks.py +++ b/Lib/asyncio/tasks.py @@ -24,6 +24,7 @@ from . import coroutines from . import events from . import exceptions from . import futures +from . import timeouts from .coroutines import _is_coroutine # Helper to generate new task names @@ -437,65 +438,44 @@ async def wait_for(fut, timeout): If the wait is cancelled, the task is also cancelled. + If the task supresses the cancellation and returns a value instead, + that value is returned. + This function is a coroutine. """ - loop = events.get_running_loop() + # The special case for timeout <= 0 is for the following case: + # + # async def test_waitfor(): + # func_started = False + # + # async def func(): + # nonlocal func_started + # func_started = True + # + # try: + # await asyncio.wait_for(func(), 0) + # except asyncio.TimeoutError: + # assert not func_started + # else: + # assert False + # + # asyncio.run(test_waitfor()) - if timeout is None: - return await fut - if timeout <= 0: - fut = ensure_future(fut, loop=loop) + if timeout is not None and timeout <= 0: + fut = ensure_future(fut) if fut.done(): return fut.result() - await _cancel_and_wait(fut, loop=loop) + await _cancel_and_wait(fut) try: return fut.result() except exceptions.CancelledError as exc: - raise exceptions.TimeoutError() from exc - - waiter = loop.create_future() - timeout_handle = loop.call_later(timeout, _release_waiter, waiter) - cb = functools.partial(_release_waiter, waiter) - - fut = ensure_future(fut, loop=loop) - fut.add_done_callback(cb) - - try: - # wait until the future completes or the timeout - try: - await waiter - except exceptions.CancelledError: - if fut.done(): - return fut.result() - else: - fut.remove_done_callback(cb) - # We must ensure that the task is not running - # after wait_for() returns. - # See https://bugs.python.org/issue32751 - await _cancel_and_wait(fut, loop=loop) - raise - - if fut.done(): - return fut.result() - else: - fut.remove_done_callback(cb) - # We must ensure that the task is not running - # after wait_for() returns. - # See https://bugs.python.org/issue32751 - await _cancel_and_wait(fut, loop=loop) - # In case task cancellation failed with some - # exception, we should re-raise it - # See https://bugs.python.org/issue40607 - try: - return fut.result() - except exceptions.CancelledError as exc: - raise exceptions.TimeoutError() from exc - finally: - timeout_handle.cancel() + raise TimeoutError from exc + async with timeouts.timeout(timeout): + return await fut async def _wait(fs, timeout, return_when, loop): """Internal helper for wait(). @@ -541,9 +521,10 @@ async def _wait(fs, timeout, return_when, loop): return done, pending -async def _cancel_and_wait(fut, loop): +async def _cancel_and_wait(fut): """Cancel the *fut* future or task and wait until it completes.""" + loop = events.get_running_loop() waiter = loop.create_future() cb = functools.partial(_release_waiter, waiter) fut.add_done_callback(cb) |