Subject: Re: [PATCH 3/6] completion: return the index of found word from __git_find_on_cmdline()

From: SZEDER Gábor <[email-masked]>
Date: Fri, 18 Oct 2019 16:37:28 +0200

On Thu, Oct 17, 2019 at 01:52:27PM -0400, Eric Sunshine wrote:
> >  __git_find_on_cmdline ()
> >  {
> > -       local word c=1
> > +       local word c=1 show_idx
> > +
> > +       while test $# -gt 1; do
> > +               case "$1" in
> > +               --show-idx)     show_idx=y ;;
> > +               *)              return 1 ;;
> 
> Should this emit an error message to aid a person debugging a test
> which fails on a call to __git_find_on_cmdline()? For instance:
> 
>     echo "unrecognized option/argument: $1" >&2
>     return 1
>     ;;
> 
> or something...

When debugging the completion script I frequently resort to 'echo >&2
"<msg>"', for lack of better options.  However, I intentionally did
not add an error message like that here, or in any similar option
parsing loops before, because due to a bug it might spew such a
message to standard error during regular completion (i.e. not during
debugging).

And printing anything to standard error during completion is
inherently bad: it disrupts the command line, can't be deleted (you
hit backspace, and in the terminal it looks as if the error message
was deleted, but in reality it's the command you've already entered
that gets deleted), and the user is eventually fored to Ctrl-C and
start over most of the time.  Well, at least I always end up hitting
Ctrl-C and start over.  Remaining silent about the unrecognized option
is in my opinion better, because then the completion script usually
does nothing, and Bash falls back to filename completion.  Yeah,
that's not ideal, but at least the user can easily correct it and
finish entering the command.