Re: [PATCH] test-lib: allow short options to be stacked

From: Matheus Tavares Bernardino <matheus.bernardino@usp.br>
Date: Mar 21, 2020, 18:50 UTC
Message-ID: <CAHd-oW4cGEwyge+BPRGiOsmMxr5ne9Ufk-BOM4EgG_i6qTxxMg@mail.gmail.com>
In-Reply-To: <20200321062611.GA1441446@coredump.intra.peff.net>

On Sat, Mar 21, 2020 at 3:26 AM Jeff King <peff@peff.net> wrote:

Show 10 quoted lines

>
> On Sat, Mar 21, 2020 at 12:07:05AM -0300, Matheus Tavares wrote:
>
> > In cases like this, CLIs usually allow the short options to be stacked
> > in a single argument, for convenience and agility. Let's add this
> > feature to test-lib, allowing the above command to be run as:
>
> Most getopt implementations I've seen call this "bundling" rather than
> "stacking" (I don't care too much either way, but Junio mentioned being
> confused at the name).

Yeah, "stacking" wasn't the best word choice. I will replace it by "bundling" then, thanks.

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>
> > +     case "$opt" in
> > +     --*)
> > +             parse_option "$opt" ;;
> > +     -?*)
> > +             # stacked short options must be fed separately to parse_option
> > +             for c in $(echo "${opt#-}" | sed 's/./& /g')
> > +             do
> > +                     parse_option "-$c"
> > +             done
>
> I wondered if we could do this without the extra process. This works:
>
>   opt=${opt#-}
>   while test -n "$opt"
>   do
>         extra=${opt#?}
>         this=${opt%$extra}
>         opt=$extra
>         parse_option "-$this"
>   done
>
> It's a little convoluted. I'm not sure if saving a process per unbundled
> short option is worth it.

I quite liked this alternative with builtins. It's a little more verbose, but it remains very clear.

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> What happens to bundled short options with arguments? I think "-r" is
> the only one. We don't allow "stuck" short options like "-r5", so we
> don't have to worry about feeding non-option bits to parse_option(). It
> looks like we'd only examine $store_arg_to outside of the short-option
> loop, so we'd treat:
>
>   ./t1234-foo.sh -vrix 5
>
> the same as:
>
>   ./t1234-foo.sh -v -r 5 -i -x

Yes. I just thought, though, that if another "short option with arguments" gets added in the future, the bundle would not work correctly. I don't think we need to be prepared for such a scenario now, but ...

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> which seems reasonable. But:
>
>   ./t1234-foo.sh -rr 5 6
>
> would get garbled.

... we could prohibit using more than one "short option with arguments" in the same bundle. This would not only solve the problem for "-rr 5 6"[1] but also for the scenario of future new options. And it's quite simple to implement, we just have to check whether $store_arg_to is set before setting it to another value. I'll try that for v2.

[1]: Someone that used '-rr 5 6' might have wanted the script to run *both* tests 5 and 6. But I don't think we need to support that now, since '-r 5 -r 6' doesn't do that as well (instead, the last value overrides all previous ones).