New submission from Matthias Fripp <[email protected]>:
The code below demonstrates this bug.
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--list-arg', nargs='+', default=[])
parser.parse_known_args(['--list-arg', 'a', '--text-arg=hello world'])
The result should be (Namespace(list_arg=['a']), ['--text-arg=hello world']),
but is actually (Namespace(list_arg=['a', '--text-arg=hello world']), []).
i.e., --list-arg consumes the next argument if that argument hasn't been
defined and uses an equal sign and has a space in the assigned value.
Note that both of the following work correctly:
parser.parse_known_args(['--list-arg', 'a', '--text-arg', 'hello world'])
parser.parse_known_args(['--list-arg', 'a', '--text-arg=hello'])
Further, the next line should cause an error, but doesn't, due to the behavior
noted above:
parser.parse_args(['--list-arg', 'a', '--text-arg=hello world'])
----------
components: Library (Lib)
messages: 323458
nosy: Matthias Fripp
priority: normal
severity: normal
status: open
title: arparse.ArgumentParser misparses list arguments followed by undefined
arguments
type: behavior
versions: Python 2.7, Python 3.4, Python 3.5, Python 3.6, Python 3.7, Python 3.8
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Python tracker <[email protected]>
<https://bugs.python.org/issue34390>
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