[issue26967] argparse: allow_abbrev=False stops -vv from working

2016-05-05 Thread Michael Kruse 

New submission from Michael Kruse:

#! /usr/bin/env python3
import argparse

parser = argparse.ArgumentParser(allow_abbrev=True)
parser.add_argument('-v', '--verbose', action='count')
print(parser.parse_args(['-vv']))

parser = argparse.ArgumentParser(allow_abbrev=False)
parser.add_argument('-v', '--verbose', action='count')
print(parser.parse_args(['-vv']))


Observed Output:
Namespace(verbose=2)
usage: test.py [-h] [-v]
test.py: error: unrecognized arguments: -vv


Expected Output:
Namespace(verbose=2)
Namespace(verbose=2)

--
components: Library (Lib)
messages: 264915
nosy: meinersbur
priority: normal
severity: normal
status: open
title: argparse: allow_abbrev=False stops -vv from working
type: behavior
versions: Python 3.5

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[issue26967] argparse: allow_abbrev=False stops -vv from working

2016-05-06 Thread Michael Kruse 

Michael Kruse added the comment:

I think the allow_abbrev option should be orthogonal on how short options are 
parsed. I am using parse_known_args() to forward the unrecognized args to 
another program, therefore allow_abbrev=False is essential.

There is a special handling for short options in the consume_optional and 
_get_option_tuples to allow them being concatenated with one dash, as commonly 
done with short options (eg. "tar -czf file"). I interpret allow_abbrev as an 
option to avoid matching non-exiting options that should be forwarded to the 
other program; '-vv' is an existing option with the same meaning as '-v -v'.

This would also mean that parse_known_args(['-vz']) (where '-v' is a registered 
argument, but '-z' is not) matches '-v' and returns '-z' as unknown argument; 
but I don't know whether you want to go that far. It is difficult to interpret 
whether '-verify' should mean '-v -e -r -i -f -y' or '--verify' (but this is 
why there are double-dash options), especially when the first letter is not a 
registered short option.

--

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