[issue32027] argparse allow_abbrev option also controls short flag combinations

[Jörn Hees]

New submission from Jörn Hees <nrej9TyO at joernhees.de>:

The allow_abbrev option (default True) currently is documented like this (https://docs.python.org/3/library/argparse.html#allow-abbrev):
> Normally, when you pass an argument list to the parse_args() method of an ArgumentParser, it recognizes abbreviations of long options.

However, it also controls combinations of short options and especially the combination of flags (store_const) like `-a -b` as `-ab`.

Example snippet for testing:

import argparse
import sys

parser = argparse.ArgumentParser(
    allow_abbrev=False
)
parser.add_argument('-a', action='store_true')
parser.add_argument('-b', action='store_true')
parser.add_argument('x', nargs='*')
parser.parse_args('-a -b foo bar'.split())
parser.parse_args('-ab foo bar'.split())


As you can see the 2nd parse will fail if allow_abbrev=False.

This issue is either a doc issue only or an unintended combination of long option shortening and (the way more common) flag combinations. When i deactivated this in my code, i wanted to disable the (nice to have) long option shortening, but i unintentionally also deactivated (MUST have) short flag combinations.

----------
assignee: docs at python
components: Documentation, Library (Lib)
messages: 306229
nosy: docs at python, joern
priority: normal
severity: normal
status: open
title: argparse allow_abbrev option also controls short flag combinations
versions: Python 3.5, Python 3.6, Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue32027>
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