python3 argparse autocomplete fail - bash

Question

i find some strange thing when i use arparse in python3.
#!/usr/bin/env python3
import argparse
def create_parser():
p = argparse.ArgumentParser(add_help=True)
p.add_argument('-i', help='i parameter', required=True)
p.add_argument('-m', help='m parameter', required=True)
return p
if __name__ == '__main__':
p = create_parser()
n = p.parse_args()
print(n)
when i try launch it with
python3 ./script.py -i ./some_folder/some_file -m ./
bash autocomplete work with '-i' parameter, but not work with '-m'. If i rename '-m' to '-me' for example, all works good.
In bash i try launch other commands with '-m' parameter, but it not work only with argparse. Where can there be a mistake here?

Answer 1

What happens here is that the autocompletion for the python3 comand kicks in:
$ complete | grep python
complete -F _python python2
complete -F _python python3
complete -F _python python
The function _python that handles it should look like this:
$ type _python
_python is a function
_python ()
{
local cur prev words cword;
_init_completion || return;
case $prev in
-'?' | -h | --help | -V | --version | -c)
return 0
;;
-m)
_python_modules "$1";
return 0
;;
-Q)
COMPREPLY=($( compgen -W "old new warn warnall" -- "$cur" ));
return 0
;;
-W)
COMPREPLY=($( compgen -W "ignore default all module once error" -- "$cur" ));
return 0
;;
!(?(*/)python*([0-9.])|-?))
[[ $cword -lt 2 || ${words[cword-2]} != -#(Q|W) ]] && _filedir
;;
esac;
local i;
for ((i=0; i < ${#words[#]}-1; i++ ))
do
if [[ ${words[i]} == -c ]]; then
_filedir;
fi;
done;
if [[ "$cur" != -* ]]; then
_filedir 'py?([co])';
else
COMPREPLY=($( compgen -W '$( _parse_help "$1" -h )' -- "$cur" ));
fi;
return 0
}
The completion function treats the -m flag the same wheather it shows up as argument to python or to the script, so it tries to complete with a list of module names.
One way around this would be to use an alias for the python3 command that does not trigger the completion, e.g:
$ alias py3=python3
To make this persistent you can put it in your ~/.bashrc. Then you can use
$ py3 ./script.py -i ./some_folder/some_file -m ./[TAB]
which will use filename completion.
Or rename the -m flag to something else.