_xspecs: bad array subscript on alias completion

[okomestudio]

I'm using Bash-it (https://github.com/Bash-it/bash-it) along with bash-complete on Debian Buster, and I get an _xspecs: bad array subscript error whenever I use an alias that uses _filedir_xspec. The original ticket was filed in Bash-it: Bash-it/bash-it#1497

There is an alias

$ alias en
alias en='emacs -nw'
$ complete -p en
complete -F _alias_completion::en en

The _alias_completion::en en is a dynamically generated function by Bash-it (except the echo line, which I added only for debugging purpose and does not affect the bug):

$ type -a _alias_completion\:\:en
_alias_completion::en is a function
_alias_completion::en () 
{ 
    (( COMP_CWORD += 1 ));
    COMP_WORDS=(emacs -nw ${COMP_WORDS[@]:1});
    (( COMP_POINT -= ${#COMP_LINE} ));
    COMP_LINE=${COMP_LINE/en/emacs -nw};
    (( COMP_POINT += ${#COMP_LINE} ));
    echo [${COMP_LINE}][${COMP_CWORD}][${COMP_POINT}][${COMP_TYPE}][${COMP_KEY}][${COMP_WORDS[@]}] 1>&2;
    _filedir_xspec
}

When I use TAB after typing som to open the file named somefile, I get this:

$ en som[emacs -nw som][2][13][9][9][emacs -nw som]
bash: _xspecs: bad array subscript
efile

Note that the completion actually seems to be working (see efile following the error message), but it outputs bash: _xspecs: bad array subscript upon hitting TAB. The parameters that I echo in square brackets seem to make sense to me (though I am not actually familiar with COMP_* variables).

I am wondering if this is a bug in bash-completion.

[scop]

The bare argumentless call to _filedir_xspec looks susceptible, that function is intended to be called as a completion one so at the very least, the first argument passed to it should be the command being invoked. No idea whether the error is because of this, though, but it could be, because that ends up being as the _xspecs subscript/key.

See Troubleshooting in README.md for further debugging tips, set -x in particular.

[okomestudio]

Thank you for the response. I have looked at the source code and it looks like the issue is indeed the missing (required) argument to _filedir_xspec. I've filed a patch at Bash-it to hopefully fix the issue on their side (not entirely sure this is the only issue, since I'm not thoroughly familiar with both the code bases). I'll report back.

[okomestudio]

We have patched Bash-it to fix the issue, so this ticket is irrelevant now. Thank you very much for the tip about the argument(s) to _filedir_xspec, which helped me identify the problem!

[scop]

Glad to hear. Posted a quick note at Bash-it/bash-it@9e92ef3#r37469859