From: "René Scharfe" <rene.scharfe@lsrfire.ath.cx>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>,
Bert Wesarg <bert.wesarg@googlemail.com>,
Geoffrey Irving <irving@naml.us>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>,
Pierre Habouzit <madcoder@debian.org>
Subject: Re: [PATCH 3/3] parse-options: remove PARSE_OPT_NEGHELP
Date: Mon, 27 Feb 2012 23:26:16 +0100 [thread overview]
Message-ID: <4F4C0308.2050804@lsrfire.ath.cx> (raw)
In-Reply-To: <20120227182504.GA1600@sigill.intra.peff.net>
Am 27.02.2012 19:25, schrieb Jeff King:
> On Sat, Feb 25, 2012 at 08:15:56PM +0100, René Scharfe wrote:
>
>> diff --git a/builtin/grep.c b/builtin/grep.c
>> index e4ea900..b151467 100644
>> --- a/builtin/grep.c
>> +++ b/builtin/grep.c
>> @@ -671,7 +671,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>> struct string_list path_list = STRING_LIST_INIT_NODUP;
>> int i;
>> int dummy;
>> - int use_index = 1;
>> + int no_index = 0;
>> enum {
>> pattern_type_unspecified = 0,
>> pattern_type_bre,
>> @@ -684,9 +684,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>> struct option options[] = {
>> OPT_BOOLEAN(0, "cached",&cached,
>> "search in index instead of in the work tree"),
>> - { OPTION_BOOLEAN, 0, "index",&use_index, NULL,
>> - "finds in contents not managed by git",
>> - PARSE_OPT_NOARG | PARSE_OPT_NEGHELP },
>> + OPT_BOOL(0, "no-index",&no_index,
>> + "finds in contents not managed by git"),
>> OPT_BOOLEAN(0, "untracked",&untracked,
>> "search in both tracked and untracked files"),
>> OPT_SET_INT(0, "exclude-standard",&opt_exclude,
>> @@ -851,7 +850,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>> break; /* nothing */
>> }
>>
>> - if (use_index&& !startup_info->have_repository)
>> + if (!no_index&& !startup_info->have_repository)
[Unrelated: The whitespace in the two lines above and before ampersands
in general was damaged by Thunderbird. First time I noticed.]
> Hmm. We usually try to avoid these sorts of double negations in the
> code, as they can often make the logic hard to read. In this case, it is
> not _so_ bad, because out of the 4 uses of use_index/no_index, only one
> is "!no_index", and it is in a relatively simple conditional.
The variable could be named "unmanaged", "external" or similar instead
of "no_index". The latter just matches the option name and thus was the
obvious first choice to me.
> But I do feel like the original was slightly easier to read, and that
> getting rid of NEGHELP is restricting how the developer can express the
> options.
>
> I think your original motivation was that NEGHELP lead to confusion
> where the name of the option does not match its description. Would it be
> better to simply be explicit that an option is a reversed boolean (i.e.,
> what the user specifies on the command line and what is in the code are
> naturally opposites). Like:
>
> OPT_REVERSE_BOOL(0, "no-index",&use_index,
> "finds in contents not managed by git"),
It's better than NEGHELP, but I find your use of two negations (REVERSE
and "no-") confusing. We don't need to invent new OPT_ types for this,
by the way, we can just do this:
OPT_NEGBIT(0, "no-index", &use_index,
"finds in contents not managed by git", 1),
It certainly shortens the patch.
> Using NEGHELP, the "reverse" is between the option name and the
> description, which is very subtle. Here it is between the option name
> and the variable, which is hopefully a little more explicit (especially
> with the big REVERSE in the macro name).
We have precedence for OPT_NEGBIT in grep, although the double negations
for -h and --full-name are required because both turn off bits that
other options turn on, while for --no-index it wouldn't be strictly
needed, as there is no option that overrules it except --index.
I don't care too much either way, though. The changes from patch 2 (the
no no-no one) are not restricted to OPT_BOOL.
> I dunno. Given that there are only two uses of NEGHELP, and that they
> don't come out too badly, I don't care _too_ much. But I have seen some
> really tortured logic with double-negations like this, and I'm concerned
> that a few months down the road somebody is going to want NEGHELP (or
> something similar) in a case where it actually does really impact
> readability.
I'm curious to see a case that can be solved better using NEGHELP, but
we can always add it back if we find such a beast. I'd much rather see
it go until then because of it's non-obvious semantics.
René
next prev parent reply other threads:[~2012-02-27 22:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-25 19:07 [PATCH 0/3] parse-options: no- symmetry René Scharfe
2012-02-25 19:11 ` [PATCH 1/3] test-parse-options: convert to OPT_BOOL() René Scharfe
2012-02-25 19:14 ` [PATCH 2/3] parse-options: allow positivation of options starting, with no- René Scharfe
2012-02-26 23:32 ` Junio C Hamano
2012-02-27 8:30 ` Thomas Rast
2012-02-27 17:18 ` Junio C Hamano
2012-02-27 17:56 ` René Scharfe
2012-02-27 20:48 ` Junio C Hamano
2012-02-28 20:12 ` [PATCH 4/3] parse-options: disallow --no-no-sth René Scharfe
2012-02-28 21:15 ` Junio C Hamano
2012-02-29 18:06 ` René Scharfe
2012-02-29 19:02 ` Junio C Hamano
2012-02-25 19:15 ` [PATCH 3/3] parse-options: remove PARSE_OPT_NEGHELP René Scharfe
2012-02-27 18:25 ` Jeff King
2012-02-27 18:58 ` Junio C Hamano
2012-02-27 22:26 ` René Scharfe [this message]
2012-02-28 0:34 ` Jeff King
2012-02-28 19:06 ` [PATCH 3/3 v2] " René Scharfe
2012-02-28 19:09 ` Jeff King
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