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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	git@vger.kernel.org, "Lin Sun" <lin.sun@zoom.us>,
	"Đoàn Trần Công Danh" <congdanhqx@gmail.com>,
	"David Aguilar" <davvid@gmail.com>
Subject: Re: [PATCH 4/5] config.c: add a "tristate" helper
Date: Fri, 9 Apr 2021 16:05:25 -0400	[thread overview]
Message-ID: <YHCzhcBkqdeEMrWA@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqqa6q8tymu.fsf@gitster.g>

On Thu, Apr 08, 2021 at 11:33:13AM -0700, Junio C Hamano wrote:

> > +/**
> > + * Same as `git_parse_maybe_bool`, except that "auto" is recognized and
> > + * will return "2".
> > + */
> > +int git_parse_maybe_tristate(const char *);
> 
> A false being 0 and a true being 1 is understandable for readers
> without symbolic constant, but "2" deserves to have a symbolic
> constant, doesn't it?

I had the same thought.

This "tristate" really has four outcomes: true, false, auto, or error.
Since the caller has to then check for error or for "auto" themselves,
it feels like it is not actually making their lives any easier. I.e.,
without it:

  if (value && !strcmp(value, "auto"))
	do_auto();
  else {
	int b = git_parse_maybe_bool(value);
	if (b < 0)
		do_error();
	else if (b)
		do_true();
	else
		do_false();
  }

but with it:

  b = git_parse_maybe_tristate(value);
  if (b < 0)
        do_error();
  else if (b == 2)
        do_auto();
  else if (b)
        do_true();
  else
        do_false();

which is the same thing, swapping string comparison for a numeric one.

And a caller of git-config has the same thing: it still has to check for
"auto" in the output it gets (which it could just do via bool-or-str).

It seems like it would be more convenient if you could pass it a bool
value to turn the "auto" into. E.g., if you could do:

  b = git_parse_maybe_tristate(value, 1); /* default to "1" */
  if (b < 0)
          do_error();
  if (b)
          do_true(); /* true, or maybe "auto" */
  else
          do_false();

I dunno. That would probably be hard to represent via "git config
--type". And some callers probably do care about "auto" versus "true".

It also feels funny calling this "tristate". Aren't there other
tristates we could have besides "auto"? The command-line option is
bool-or-auto, which is descriptive. Should this use a similar name?

-Peff

  parent reply	other threads:[~2021-04-09 20:05 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-08 13:34 [PATCH 0/5] config: support --type=bool-or-auto for "tristate" parsing Ævar Arnfjörð Bjarmason
2021-04-08 13:34 ` [PATCH 1/5] config.c: add a comment about why value=NULL is true Ævar Arnfjörð Bjarmason
2021-04-08 18:10   ` Junio C Hamano
2021-04-08 13:34 ` [PATCH 2/5] config tests: test for --bool-or-str Ævar Arnfjörð Bjarmason
2021-04-08 18:21   ` Junio C Hamano
2021-04-08 23:11     ` Ævar Arnfjörð Bjarmason
2021-04-08 13:34 ` [PATCH 3/5] git-config: document --bool-or-str and --type=bool-or-str Ævar Arnfjörð Bjarmason
2021-04-08 18:22   ` Junio C Hamano
2021-04-08 13:34 ` [PATCH 4/5] config.c: add a "tristate" helper Ævar Arnfjörð Bjarmason
2021-04-08 18:33   ` Junio C Hamano
2021-04-08 23:23     ` Ævar Arnfjörð Bjarmason
2021-04-08 23:51       ` Junio C Hamano
2021-04-09  1:33         ` Ævar Arnfjörð Bjarmason
2021-04-09 12:53           ` Junio C Hamano
2021-04-08 23:54       ` Junio C Hamano
2021-04-09 20:05     ` Jeff King [this message]
2021-04-09 22:11       ` Junio C Hamano
2021-04-10  1:23         ` Jeff King
2021-04-10  1:43           ` Junio C Hamano
2021-04-08 13:34 ` [PATCH 5/5] config: add --type=bool-or-auto switch Ævar Arnfjörð Bjarmason
2021-04-08 18:36   ` Junio C Hamano

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