circuitpython/tests/extmod/uasyncio_task_exception.py

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# In MicroPython, a non-awaited task with a pending exception will raise to
# the loop's exception handler the second time it is scheduled. This is
# because without reference counting we have no way to know when the task is
# truly "non awaited" -- i.e. we only know that it wasn't awaited in the time
# it took to be re-scheduled.
# If the task _is_ subsequently awaited, then the await should succeed without
# raising.
try:
import uasyncio as asyncio
except ImportError:
try:
import asyncio
except ImportError:
print("SKIP")
raise SystemExit
def custom_handler(loop, context):
print("exception handler", type(context["exception"]).__name__)
async def main():
loop = asyncio.get_event_loop()
loop.set_exception_handler(custom_handler)
async def task():
print("raise")
raise OSError
print("create")
t = asyncio.create_task(task())
print("sleep 1")
await asyncio.sleep(0)
print("sleep 2")
await asyncio.sleep(0)
print("await")
await t # should not raise.
asyncio.run(main())