asyncio.Task fail doesn't cause to all program exit if it was set to some variable

asyncio_fail_on_task_exception.py

import asyncio
import sys
import logging

logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
sh = logging.StreamHandler()
sh.setLevel(logging.DEBUG)
logger.addHandler(sh)


def custom_exception_handler(loop, context):
    loop.default_exception_handler(context); sys.stdout.flush()
    loop.stop()
    # exception = context.get('exception')
    # raise exception


loop = asyncio.get_event_loop()
loop.set_exception_handler(custom_exception_handler)


class A:
    async def wait_and_fail(self):
        await asyncio.sleep(1)
        raise ValueError

    async def run(self, how_to_set: str):
        logger.info('task = asyncio.get_event_loop().create_task(self.wait_and_fail())')

        if how_to_set == 'field':
            self.task = asyncio.get_event_loop().create_task(self.wait_and_fail())
        elif how_to_set == 'none':
            asyncio.get_event_loop().create_task(self.wait_and_fail())
        elif how_to_set == 'var':
            task = asyncio.get_event_loop().create_task(self.wait_and_fail())
        elif how_to_set == 'list':
            [asyncio.get_event_loop().create_task(self.wait_and_fail())]
        elif how_to_set == 'list_field':
            self.tasks = [asyncio.get_event_loop().create_task(self.wait_and_fail())]
        else:
            raise ValueError

        for i in range(5):
            await asyncio.sleep(1)
            logger.info(f'i = {i}')
        logger.info('run success')


async def run_a_and_del(how_to_set):
    logger.info('start run_a_and_del')
    a = A()
    logger.info('start await a.run(set_task=set_task)')
    await a.run(how_to_set=how_to_set)
    if hasattr(a, 'task'):
        logger.info('start del a.task')
        del a.task
    if hasattr(a, 'tasks'):
        logger.info('start del a.tasks')
        del a.tasks
    logger.info('start del a')
    del a


async def main():
    # different approaches
    if 1:  # it fails with exception immediately with exit_code=1
        a = A()
        await a.run(how_to_set='none')
    elif 0:  # it finish execution and print exception in the end with exit_code=0
        a = A()
        await a.run(how_to_set='field')
    elif 0:  # it finish execution, destruct A instance and print exception in the end with exit_code=0
        await run_a_and_del(how_to_set='field')
    elif 0:  # it finish execution and print exception in the end with exit_code=0
        a = A()
        await a.run(how_to_set='var')
    elif 0:  # it fails with exception immediately with exit_code=1
        a = A()
        await a.run(how_to_set='list')
    elif 0:  # it finish execution and print exception in the end with exit_code=0
        a = A()
        await a.run(how_to_set='list_field')
    logger.info('main finish')


if __name__ == '__main__':
    asyncio.get_event_loop().run_until_complete(main())