argparse crashes with AssertionError

[spaceone]

BPO	24089
Nosy	@ncoghlan, @merwok, @dstufft, @spaceone, @miss-islington
PRs	[3.7] bpo-11874: fix assertion failure in argparse metavar handling (GH-1826) #7527 [3.6] bpo-11874: fix assertion failure in argparse metavar handling (GH-1826) #7528 [3.7] bpo-11874: fix assertion failure in argparse metavar handling (GH-1826) #7530 [2.7] bpo-11874: fix assertion failure in argparse metavar handling (GH-1826) #7553
Superseder	bpo-11874: argparse assertion failure with brackets in metavars

^{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 2015-05-05.21:06:35.932>
created_at = <Date 2015-05-01.04:45:58.188>
labels = ['library', 'type-crash']
title = 'argparse crashes with AssertionError'
updated_at = <Date 2018-06-09.01:28:05.393>
user = 'https://github.com/spaceone'

bugs.python.org fields:

activity = <Date 2018-06-09.01:28:05.393>
actor = 'miss-islington'
assignee = 'none'
closed = True
closed_date = <Date 2015-05-05.21:06:35.932>
closer = 'ned.deily'
components = ['Distutils']
creation = <Date 2015-05-01.04:45:58.188>
creator = 'spaceone'
dependencies = []
files = []
hgrepos = []
issue_num = 24089
keywords = []
message_count = 6.0
messages = ['242299', '242449', '319039', '319048', '319052', '319125']
nosy_count = 6.0
nosy_names = ['ncoghlan', 'eric.araujo', 'paul.j3', 'dstufft', 'spaceone', 'miss-islington']
pr_nums = ['7527', '7528', '7530', '7553']
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '11874'
type = 'crash'
url = 'https://bugs.python.org/issue24089'
versions = ['Python 2.7']

[spaceone]

Just add an argument with metavar='[PROTOCOL://]HOST[:PORT]' ([...] twice in the string) causes the following traceback:

Traceback (most recent call last):
  File "curl.py", line 182, in <module>
    arguments = parser.parse_args()
  File "/usr/lib/python2.7/argparse.py", line 1701, in parse_args
    args, argv = self.parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1733, in parse_known_args
    namespace, args = self._parse_known_args(args, namespace)
  File "/usr/lib/python2.7/argparse.py", line 1939, in _parse_known_args
    start_index = consume_optional(start_index)
  File "/usr/lib/python2.7/argparse.py", line 1879, in consume_optional
    take_action(action, args, option_string)
  File "/usr/lib/python2.7/argparse.py", line 1807, in take_action
    action(self, namespace, argument_values, option_string)
  File "/usr/lib/python2.7/argparse.py", line 996, in __call__
    parser.print_help()
  File "/usr/lib/python2.7/argparse.py", line 2340, in print_help
    self._print_message(self.format_help(), file)
  File "/usr/lib/python2.7/argparse.py", line 2314, in format_help
    return formatter.format_help()
  File "/usr/lib/python2.7/argparse.py", line 281, in format_help
    help = self._root_section.format_help()
  File "/usr/lib/python2.7/argparse.py", line 211, in format_help
    func(*args)
  File "/usr/lib/python2.7/argparse.py", line 332, in _format_usage
    assert ' '.join(opt_parts) == opt_usage
AssertionError

[paulj3]

It's the spaces and/or brackets in the metavar, along with a usage line that is long enough to wrap, that is raising this error.

It's a known problem.

http://bugs.python.org/issue11874

[ncoghlan]

New changeset 66f02aa by Nick Coghlan (wim glenn) in branch 'master':
bpo-11874: fix assertion failure in argparse metavar handling (GH-1826)
66f02aa

[miss-islington]

New changeset 376c272 by Miss Islington (bot) in branch '3.6':
bpo-11874: fix assertion failure in argparse metavar handling (GH-1826)
376c272

[miss-islington]

New changeset 842985f by Miss Islington (bot) in branch '3.7':
bpo-11874: fix assertion failure in argparse metavar handling (GH-1826)
842985f

[miss-islington]

New changeset 4e6bd24 by Miss Islington (bot) in branch '2.7':
bpo-11874: fix assertion failure in argparse metavar handling (GH-1826)
4e6bd24