feature request: asyncio.gather/wait cancel children on first exception

[thehesiod]

BPO	32754
Nosy	@asvetlov, @1st1, @thehesiod, @iritkatriel
Superseder	bpo-46752: Introduce task groups to asyncio and change task cancellation semantics

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2022-03-30.21:21:54.459>
created_at = <Date 2018-02-02.23:29:02.585>
labels = ['3.8', 'expert-asyncio']
title = 'feature request: asyncio.gather/wait cancel children on first exception'
updated_at = <Date 2022-03-30.21:21:54.459>
user = 'https://github.com/thehesiod'

bugs.python.org fields:

activity = <Date 2022-03-30.21:21:54.459>
actor = 'iritkatriel'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-30.21:21:54.459>
closer = 'iritkatriel'
components = ['asyncio']
creation = <Date 2018-02-02.23:29:02.585>
creator = 'thehesiod'
dependencies = []
files = []
hgrepos = []
issue_num = 32754
keywords = []
message_count = 3.0
messages = ['311527', '311528', '415672']
nosy_count = 4.0
nosy_names = ['asvetlov', 'yselivanov', 'thehesiod', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '46752'
type = None
url = 'https://bugs.python.org/issue32754'
versions = ['Python 3.8']

[thehesiod]

currently gather/wait allow you to return on the first exception and leave the children executing.

A very common use case that I have is of launching multiple tasks, and if any of them fail, then all should fail..otherwise the other tasks would continue running w/o anyone listening for the results. To accomplish this I wrote a method like the following: https://gist.github.com/thehesiod/524a1f005d0f3fb61a8952f272d8709e. I think it would be useful to many others as on optional perhaps a parameter to each of these methods.

What do you guys think?

[1st1]

I think it's a good idea and I wanted to implement it by copying TaskGroups from curio in 3.7. But then I saw Trio's nurseries and I have a few ideas about slightly different design inspired by both curio and Trio :)

I have some very WIP code that I plan to finish in a few weeks. I'll update this issue then.

[iritkatriel]

Task groups are implemented under bpo-46752.