argparse not including '--' arguments in previous optional REMAINDER argument

[JurkoGospodneti]

BPO	22223

^{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 = None
created_at = <Date 2014-08-18.09:46:02.121>
labels = ['type-bug', 'library']
title = "argparse not including '--' arguments in previous optional REMAINDER argument"
updated_at = <Date 2014-08-20.13:47:19.982>
user = 'https://bugs.python.org/JurkoGospodneti'

bugs.python.org fields:

activity = <Date 2014-08-20.13:47:19.982>
actor = 'Juraj.Ivancic'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2014-08-18.09:46:02.121>
creator = 'Jurko.Gospodneti\xc4\x87'
dependencies = []
files = []
hgrepos = []
issue_num = 22223
keywords = []
message_count = 2.0
messages = ['225484', '225485']
nosy_count = 2.0
nosy_names = ['Jurko.Gospodneti\xc4\x87', 'Juraj.Ivancic']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue22223'
versions = ['Python 2.7', 'Python 3.4']

Linked PRs

• gh-66419: Make optional arguments with nargs=REMAINDER consume all arguments #124509

[JurkoGospodneti]

If you have an optional nargs=argparse.REMAINDER argument defined
then, if specified, its value should contain all the remaining command-line content. However, it seems that value does not include later '--' arguments.

For example, the following works as expected:

import argparse
parser = argparse.ArgumentParser(prog="PROG")
parser.add_argument("--args", nargs=argparse.REMAINDER)
args = parser.parse_args("--args cmd --arg1 XX ZZ".split())
assert args.args == ["cmd", "--arg1", "XX", "ZZ"]

But the following fails with
'PROG: error: unrecognized arguments: -- ZZ':

import argparse
parser = argparse.ArgumentParser(prog="PROG")
parser.add_argument("--args", nargs=argparse.REMAINDER)
args = parser.parse_args("--args cmd --arg1 XX -- ZZ".split())
assert args.args == ["cmd", "--arg1", "XX", "--", "ZZ"]

Note that the same code works as expected when using a
positional nargs=argparse.REMAINDER arguments:

import argparse
parser = argparse.ArgumentParser(prog="PROG")
parser.add_argument("args", nargs=argparse.REMAINDER)
args = parser.parse_args("args cmd --arg1 XX ZZ".split())
assert args.args == ["cmd", "--arg1", "XX", "ZZ"]
args = parser.parse_args("args cmd --arg1 XX -- ZZ".split())
assert args.args == ["cmd", "--arg1", "XX", "--", "ZZ"]

But that, of course, does not allow us to have the args value
start with something like "--blah" that looks like an optional
argument.

Hope this helps.

Best regards,
Jurko Gospodnetić

[JurkoGospodneti]

Might be related to the following issues:

http://bugs.python.org/issue9571
http://bugs.python.org/issue13922

[serhiy-storchaka]

REMAINDER is currently undocumented (see bpo-17050/gh-61252), but the proposed change looks right. This would allow to use REMAINDER to simulate a subparser with option as the command (currently the subparser machinery does not support this). I believe it is just an omission that this was not supported before.