extmod/uasyncio: wait_for cancellation bugs #5797
Description
CancelledError forwarding if wait_for got cancelled (not the task it awaits):
Your assumption "# Ignore CancelledError from aw, it's probably due to timeout" in funcy.py line 20
micropython/extmod/uasyncio/funcs.py
Line 20 in ad004db
As you can see in the testcase "wait_for.test_cancellation_forwarded", if you cancel the caller task of "wait_for", the coro awaited by "wait_for" gets correctly cancelled, but the caller of "wait_for" never gets the Exception raised. The CancelledError gets swallowed by "wait_for" instead of forwarding it.
Wait_for also behaves incorrectly if CancelldError Exceptions are caught inside the task it awaits because they don't get raised to wait_for anymore. However Cpython does also raise those to wait_for even if they are caught in the task wait_for awaits.
All my wait_for testcases (working on upy and cpy) are here: https://gist.github.com/kevinkk525/3313a8d2763031a705e37d1748d1d996
The one in question for all bugs mentioned:
async def test_cancellation_forwarded(catch=False, catch_inside=False):
res = [False, False]
async def wait():
nonlocal res
try:
await asyncio.wait_for(awaiting(2, catch_inside), 0.5)
except asyncio.TimeoutError:
dprint("Got timeout error")
res[0] = asyncio.TimeoutError
raise
except asyncio.CancelledError:
dprint("Got canceled")
if catch:
res[0] = True
else:
raise
async def killer(t):
dprint("killer started")
await asyncio.sleep(0.2)
dprint("killing wait()")
t.cancel()
t = asyncio.create_task(wait())
k = asyncio.create_task(killer(t))
try:
await t
except asyncio.CancelledError:
dprint("waiting got cancelled")
res[1] = asyncio.CancelledError
return res