[argparse] Add required argument to add_subparsers

[memeplex]

BPO	26510
Nosy	@ned-deily, @merwok, @asottile, @miss-islington
PRs	bpo-26510: Allow argparse add_subparsers to take required kwarg. #3027 bpo-33109: argparse subparsers are once again not required by default #6919 [3.7] bpo-33109: argparse subparsers are once again not required by default (GH-6919) #7089 bpo-33109: Remove now-obsolete What's New entry for bpo-26510. #7609 [3.7] bpo-33109: Remove now-obsolete What's New entry for bpo-26510. (GH-7609) #7610 bpo-26510: Add versionchanged for required arg of add_subparsers #16588 [3.8] bpo-26510: Add versionchanged for required arg of add_subparsers (GH-16588) #16608 [3.7] bpo-26510: Add versionchanged for required arg of add_subparsers (GH-16588) #16609

^{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 = 'https://github.com/merwok'
closed_at = <Date 2017-09-20.21:36:42.299>
created_at = <Date 2016-03-08.13:56:01.475>
labels = ['3.7', 'type-feature', 'library']
title = '[argparse] Add required argument to add_subparsers'
updated_at = <Date 2019-10-15.07:30:26.268>
user = 'https://bugs.python.org/memeplex'

bugs.python.org fields:

activity = <Date 2019-10-15.07:30:26.268>
actor = 'ned.deily'
assignee = 'eric.araujo'
closed = True
closed_date = <Date 2017-09-20.21:36:42.299>
closer = 'eric.araujo'
components = ['Library (Lib)']
creation = <Date 2016-03-08.13:56:01.475>
creator = 'memeplex'
dependencies = []
files = []
hgrepos = []
issue_num = 26510
keywords = []
message_count = 12.0
messages = ['261358', '261535', '300282', '302660', '317500', '317512', '319265', '319267', '354060', '354061', '354062', '354700']
nosy_count = 7.0
nosy_names = ['bethard', 'ned.deily', 'eric.araujo', 'memeplex', 'paul.j3', 'Anthony Sottile', 'miss-islington']
pr_nums = ['3027', '6919', '7089', '7609', '7610', '16588', '16608', '16609']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue26510'
versions = ['Python 3.7']

[memeplex]

It's useful in combination with dest. Currently you have to set required as an attribute. This is not only inconsistent but not even documented as a valid usage (in general, it's not clear from the docs whether attribute setting -vs argument passing- is a valid usage).

[paulj3]

This has been raised before. I think

http://bugs.python.org/issue9253

is the correct issue.

It used to be that 'subparsers' were required. But there was a change in how 'required' arguments were tested, and 'subparsers' fell through the cracks. Now subparsers are optional (at least the parser doesn't raise an error). The temporary fix is to set the 'required' attribute after creation.

I proposed that the default be 'required=True', and that we be allowed to set the parameter. But that patch, like many others, has languished.

[asottile]

I've added a patch for this #3027

Would love to get a review so it could be included

[merwok]

New changeset aaf6fc0 by Éric Araujo (Anthony Sottile) in branch 'master':
bpo-26510: make argparse subparsers required by default (bpo-3027)
aaf6fc0

[ned-deily]

New changeset 8ebf5ce by Ned Deily in branch 'master':
bpo-33109: argparse subparsers are once again not required by default (GH-6919)
8ebf5ce

[ned-deily]

New changeset dd7a255 by Ned Deily (Miss Islington (bot)) in branch '3.7':
bpo-33109: argparse subparsers are once again not required by default (GH-6919) (GH-7089)
dd7a255

[ned-deily]

New changeset ef057bf by Ned Deily in branch 'master':
bpo-33109: Remove now-obsolete What's New entry for bpo-26510. (GH-7609)
ef057bf

[ned-deily]

New changeset a73399d by Ned Deily (Miss Islington (bot)) in branch '3.7':
bpo-33109: Remove now-obsolete What's New entry for bpo-26510. (GH-7609) (GH-7610)
a73399d

[miss-islington]

New changeset 9e71917 by Miss Islington (bot) (Adam J. Stewart) in branch 'master':
bpo-26510: Add versionchanged for required arg of add_subparsers (GH-16588)
9e71917

[miss-islington]

New changeset 50b8d57 by Miss Islington (bot) in branch '3.7':
bpo-26510: Add versionchanged for required arg of add_subparsers (GH-16588)
50b8d57

[miss-islington]

New changeset f19b4d7 by Miss Islington (bot) in branch '3.8':
bpo-26510: Add versionchanged for required arg of add_subparsers (GH-16588)
f19b4d7

[ned-deily]

New changeset f168c17 by Ned Deily (Miss Islington (bot)) in branch '3.7':
bpo-26510: Add versionchanged for required arg of add_subparsers (GH-16588)
f168c17