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From: Eric Sunshine <sunshine@sunshineco.com>
To: Phillip Wood <phillip.wood@dunelm.org.uk>
Cc: Git List <git@vger.kernel.org>,
	Junio C Hamano <gitster@pobox.com>,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH v4 2/5] am: improve author-script error reporting
Date: Sun, 4 Nov 2018 00:12:13 -0400	[thread overview]
Message-ID: <CAPig+cRBwkKGtzY6CwZiKb1mef0a-9F+O24d0R8ZfsRb5ssUbA@mail.gmail.com> (raw)
In-Reply-To: <20181031101556.27169-3-phillip.wood@talktalk.net>

On Wed, Oct 31, 2018 at 6:16 AM Phillip Wood <phillip.wood@talktalk.net> wrote:
> diff --git a/builtin/am.c b/builtin/am.c
> @@ -308,6 +312,7 @@ static int read_author_script(struct am_state *state)
> +       int i, name_i = -2, email_i = -2, date_i = -2, err = 0;
> @@ -326,14 +331,38 @@ static int read_author_script(struct am_state *state)
> +       for (i = 0; i < kv.nr; i++) {
> +               if (!strcmp(kv.items[i].string, "GIT_AUTHOR_NAME")) {
> +                       if (name_i >= 0)
> +                               name_i = error(_("'GIT_AUTHOR_NAME' already given"));
> +                       else
> +                               name_i = i;
> +               }
> +               ...
> +       }
> +       if (name_i == -2)
> +               error(_("missing 'GIT_AUTHOR_NAME'"));
> +       ...
> +       if (date_i < 0 || email_i < 0 || date_i < 0 || err)
>                 goto finish;
> +       state->author_name = kv.items[name_i].util;
> +       ...
>         retval = 0;
>  finish:
>         string_list_clear(&kv, !!retval);

Junio labeled the "-2" trick "cute", and while it is optimal in that
it only traverses the key/value list once, it also increases cognitive
load since the reader has to spend a good deal more brain cycles
understanding what is going on than would be the case with simpler
(and less noisily repetitive) code.

An alternative would be to make the code trivially easy to understand,
though a bit more costly, but that expense should be negligible since
this file should always be tiny, containing very few key/value pairs,
and it's not timing critical code anyhow. For instance:

static char *find(struct string_list *kv, const char *key)
{
    const char *val = NULL;
    int i;
    for (i = 0; i < kv.nr; i++) {
        if (!strcmp(kv.items[i].string, key)) {
            if (val) {
                error(_("duplicate %s"), key);
                return NULL;
            }
            val = kv.items[i].util;
        }
    }
    if (!val)
        error(_("missing %s"), key);
    return val;
}

static int read_author_script(struct am_state *state)
{
    ...
    char *name, *email, *date;
    ...
    name = find(&kv, "GIT_AUTHOR_NAME");
    email = find(&kv, "GIT_AUTHOR_EMAIL");
    date = find(&kv, "GIT_AUTHOR_DATE");
    if (name && email && date) {
        state->author_name = name;
        state->author_email = email;
        state->author_date = date;
        retval = 0;
    }
    string_list_clear&kv, !!retval);
    ...

  reply	other threads:[~2018-11-04  4:12 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-12 10:10 [PATCH 0/3] am/rebase: share read_author_script() Phillip Wood
2018-09-12 10:10 ` [PATCH 1/3] am: rename read_author_script() Phillip Wood
2018-09-12 10:10 ` [PATCH 2/3] add read_author_script() to libgit Phillip Wood
2018-09-13 23:49   ` Eric Sunshine
2018-10-10 10:14     ` Phillip Wood
2018-10-10 10:22       ` Eric Sunshine
2018-09-12 10:10 ` [PATCH 3/3] sequencer: use read_author_script() Phillip Wood
2018-09-12 12:14   ` Eric Sunshine
2018-09-14  0:31   ` Eric Sunshine
2018-10-10 10:35     ` Phillip Wood
2018-10-18 10:00 ` [PATCH v2 0/5] am/rebase: share read_author_script() Phillip Wood
2018-10-18 10:00   ` [PATCH v2 1/5] am: don't die in read_author_script() Phillip Wood
2018-10-25  8:44     ` Junio C Hamano
2018-10-18 10:00   ` [PATCH v2 2/5] am: improve author-script error reporting Phillip Wood
2018-10-25  8:55     ` Junio C Hamano
2018-10-18 10:00   ` [PATCH v2 3/5] am: rename read_author_script() Phillip Wood
2018-10-18 10:00   ` [PATCH v2 4/5] add read_author_script() to libgit Phillip Wood
2018-10-18 10:00   ` [PATCH v2 5/5] sequencer: use read_author_script() Phillip Wood
2018-10-25  8:59   ` [PATCH v2 0/5] am/rebase: share read_author_script() Junio C Hamano
2018-10-26  9:00     ` Phillip Wood
2018-10-26 13:32       ` Junio C Hamano
2018-10-30 10:39 ` [PATCH v3 " Phillip Wood
2018-10-30 10:39   ` [PATCH v3 1/5] am: don't die in read_author_script() Phillip Wood
2018-10-30 10:39   ` [PATCH v3 2/5] am: improve author-script error reporting Phillip Wood
2018-10-30 10:39   ` [PATCH v3 3/5] am: rename read_author_script() Phillip Wood
2018-10-30 10:39   ` [PATCH v3 4/5] add read_author_script() to libgit Phillip Wood
2018-10-30 10:39   ` [PATCH v3 5/5] sequencer: use read_author_script() Phillip Wood
2018-10-31  2:50   ` [PATCH v3 0/5] am/rebase: share read_author_script() Junio C Hamano
2018-10-31 10:14     ` Phillip Wood
2018-10-31 10:15 ` [PATCH v4 " Phillip Wood
2018-10-31 10:15   ` [PATCH v4 1/5] am: don't die in read_author_script() Phillip Wood
2018-10-31 10:15   ` [PATCH v4 2/5] am: improve author-script error reporting Phillip Wood
2018-11-04  4:12     ` Eric Sunshine [this message]
2018-11-05  1:53       ` Junio C Hamano
2018-10-31 10:15   ` [PATCH v4 3/5] am: rename read_author_script() Phillip Wood
2018-10-31 10:15   ` [PATCH v4 4/5] add read_author_script() to libgit Phillip Wood
2018-10-31 10:15   ` [PATCH v4 5/5] sequencer: use read_author_script() Phillip Wood
2018-11-01  3:01   ` [PATCH v4 0/5] am/rebase: share read_author_script() Junio C Hamano
2018-11-01  3:12     ` [PATCH v4fixed 2/5] am: improve author-script error reporting Junio C Hamano
2018-11-01  3:12       ` [PATCH v4fixed 4/5] add read_author_script() to libgit Junio C Hamano
2018-11-01 16:27     ` [PATCH v4 0/5] am/rebase: share read_author_script() Phillip Wood

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