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From: Junio C Hamano <gitster@pobox.com>
To: Paul Tan <pyokagan@gmail.com>
Cc: Git List <git@vger.kernel.org>,
	Stefan Beller <sbeller@google.com>,
	Johannes Schindelin <johannes.schindelin@gmx.de>,
	Stephen Robin <stephen.robin@gmail.com>
Subject: Re: [PATCH v2 02/19] parse-options-cb: implement parse_opt_pass_argv_array()
Date: Wed, 10 Jun 2015 01:03:54 -0700	[thread overview]
Message-ID: <xmqqy4jst2fp.fsf@gitster.dls.corp.google.com> (raw)
In-Reply-To: <CACRoPnRVjNseXPOxKe4_3rnKXmAYeA80iCHY3o8euWA=EUX6hA@mail.gmail.com> (Paul Tan's message of "Wed, 10 Jun 2015 15:11:01 +0800")

Paul Tan <pyokagan@gmail.com> writes:

> I don't see how it feels iffy.

That is largely a taste thing.  And a good taste matters.

What is iffy is to use strbuf as an external interface between the
implementation of the parse_opt_pass() API function and its users.

I would expect that no users of the parse_opt_pass() would ever take
advantage of the fact that the value they are using is implemented
as a strbuf, allowing them to use the family of functions in the
strbuf API to further manipulate it.  All users you added wants to
use a plain vanilla string, and only because you used strbuf as the
interface element, they have to say "var.buf" to get to the value
they want to use.

> The purpose of using strbufs (and
> argv_arrays) is to avoid error-prone manual memory management.

It is a good idea to use strbuf as an implementation detail of
parse_opt_pass() function.  After all, safer, easier and efficient
manipulation of strings is why we added the strbuf API to the system
in the first place.

But it is a different matter to expose that as an API element when
the recipient is not going to benefit.

In other words, callers of the API designed with a better taste
would look more like this:

	static const char *opt_diffstat;

	static struct option pull_options[] = {
        	...
                { OPTION_CALLBACK, 'n', NULL, &opt_diffstat, NULL,
		  N_("do not show a diffstat at the end of the merge"),
		  PARSE_OPT_NOARG | PARSE_OPT_NONEG, parse_opt_pass
        	},
		...
	};

	static int run_merge(void)
        {
        	...
                if (opt_diffstat)
                	argv_array_push(&args, opt_diffstat);
		...
	}

That way, they do not have to define strbuf variables and
dereference the value as opt_diffstat.buf.

And the implementation of the API element is not all that different
from what you wrote:

	int parse_opt_pass(const struct options *opt, const char *arg, int unset)
	{
		struct strbuf sb = STRBUF_INIT;
		char **value = opt->value;

		if (*value)
                	free(*value);
		if (opt->long_name) {
                	strbuf_addf(&sb, "--%s%s",
                        	    unset ? "no-" : "",
                                    opt->long_name);
			...
                }
                ...
                *value = strbuf_detach(&sb, NULL);
		return 0;
	}

  reply	other threads:[~2015-06-10  8:04 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-03  6:48 [PATCH v2 00/19] Make git-pull a builtin Paul Tan
2015-06-03  6:48 ` [PATCH v2 01/19] parse-options-cb: implement parse_opt_pass_strbuf() Paul Tan
2015-06-09 23:11   ` Junio C Hamano
2015-06-03  6:48 ` [PATCH v2 02/19] parse-options-cb: implement parse_opt_pass_argv_array() Paul Tan
2015-06-03 16:56   ` Stefan Beller
2015-06-09 23:16   ` Junio C Hamano
2015-06-10  7:11     ` Paul Tan
2015-06-10  8:03       ` Junio C Hamano [this message]
2015-06-03  6:48 ` [PATCH v2 03/19] argv-array: implement argv_array_pushv() Paul Tan
2015-06-03  6:48 ` [PATCH v2 04/19] pull: implement skeletal builtin pull Paul Tan
2015-06-10  0:23   ` Junio C Hamano
2015-06-03  6:48 ` [PATCH v2 05/19] pull: implement fetch + merge Paul Tan
2015-06-09 23:27   ` Junio C Hamano
2015-06-03  6:48 ` [PATCH v2 06/19] pull: pass verbosity, --progress flags to fetch and merge Paul Tan
2015-06-09 23:36   ` Junio C Hamano
2015-06-03  6:48 ` [PATCH v2 07/19] pull: pass git-merge's options to git-merge Paul Tan
2015-06-03  6:48 ` [PATCH v2 08/19] pull: pass git-fetch's options to git-fetch Paul Tan
2015-06-03 17:16   ` Stefan Beller
2015-06-03  6:48 ` [PATCH v2 09/19] pull: error on no merge candidates Paul Tan
2015-06-09 23:56   ` Junio C Hamano
2015-06-13  5:52     ` Paul Tan
2015-06-03  6:48 ` [PATCH v2 10/19] pull: support pull.ff config Paul Tan
2015-06-09 23:59   ` Junio C Hamano
2015-06-03  6:48 ` [PATCH v2 11/19] pull: check if in unresolved merge state Paul Tan
2015-06-10  1:29   ` Junio C Hamano
2015-06-10 14:38     ` Junio C Hamano
2015-06-10 15:12       ` Paul Tan
2015-06-10 17:14         ` Junio C Hamano
2015-06-14  7:44           ` Paul Tan
2015-06-03  6:48 ` [PATCH v2 12/19] pull: fast-forward working tree if head is updated Paul Tan
2015-06-03  6:48 ` [PATCH v2 13/19] pull: implement pulling into an unborn branch Paul Tan
2015-06-10  1:31   ` Junio C Hamano
2015-06-03  6:48 ` [PATCH v2 14/19] pull: set reflog message Paul Tan
2015-06-03  6:48 ` [PATCH v2 15/19] pull: teach git pull about --rebase Paul Tan
2015-06-10  1:56   ` Junio C Hamano
2015-06-10  7:55     ` Paul Tan
2015-06-10 14:44       ` Junio C Hamano
2015-06-10 15:35         ` Paul Tan
2015-06-10 16:13           ` Junio C Hamano
2015-06-10 23:02   ` Junio C Hamano
2015-06-03  6:49 ` [PATCH v2 16/19] pull: configure --rebase via branch.<name>.rebase or pull.rebase Paul Tan
2015-06-03  6:49 ` [PATCH v2 17/19] pull --rebase: exit early when the working directory is dirty Paul Tan
2015-06-03 10:27   ` Kevin Daudt
2015-06-10  5:53     ` Kevin Daudt
2015-06-03  6:49 ` [PATCH v2 18/19] pull --rebase: error on no merge candidate cases Paul Tan
2015-06-03 17:38   ` Stefan Beller
2015-06-03  6:49 ` [PATCH v2 19/19] pull: remove redirection to git-pull.sh Paul Tan
2015-06-03 17:49   ` Stefan Beller

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