Re: [PATCH 07/15] remote-mediawiki tests: guard test_cmp with test_path_is_file

From: Junio C Hamano <gitster@pobox.com>
To: Eric Sunshine <sunshine@sunshineco.com>
Cc: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Git List" <git@vger.kernel.org>,
	"Matthieu Moy" <git@matthieu-moy.fr>,
	"Johannes Schindelin" <Johannes.Schindelin@gmx.de>,
	"Antoine Beaupré" <anarcat@debian.org>,
	"Simon Legner" <Simon.Legner@gmail.com>
Subject: Re: [PATCH 07/15] remote-mediawiki tests: guard test_cmp with test_path_is_file
Date: Wed, 16 Sep 2020 14:13:55 -0700	[thread overview]
Message-ID: <xmqq4knxwhkc.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <CAPig+cRg2tuOiQH_CQoHMjkX2gbRPJoV8NPJZnu3=bfo4wk-cQ@mail.gmail.com> (Eric Sunshine's message of "Wed, 16 Sep 2020 12:53:40 -0400")

Eric Sunshine <sunshine@sunshineco.com> writes:

> On Wed, Sep 16, 2020 at 8:17 AM Ævar Arnfjörð Bjarmason
> <avarab@gmail.com> wrote:
>> Change a test that used a plain test_cmp to first check the file(s)
>> using test_path_is_file. If some of these file(s) don't exist (as
>> happened to me during debugging), test_cmp will emit a way less useful
>> message about the failure.
>
> An alternative would be to update test_cmp() to present a more helpful
> error message so that all test scripts can benefit rather than just
> this script. By the way, were you testing with a reasonably recent
> version of Git? I ask because test_cmp() was updated not long ago to
> provide better diagnostics when one of the files is missing.
>
> [1]: d572f52a64 (test_cmp: diagnose incorrect arguments, 2020-08-09)

Yes, you did this with the commit,

test_cmp() {
	test $# -eq 2 || BUG "test_cmp requires two arguments"
	if ! eval "$GIT_TEST_CMP" '"$@"'
	then
		test "x$1" = x- || test -e "$1" || BUG "test_cmp '$1' missing"
		test "x$2" = x- || test -e "$2" || BUG "test_cmp '$2' missing"
		return 1
	fi
}

and I do not immediately see why "test -e" shouldn't be "test -f".
It should ideally be "stdin is OK, otherwise it must be a readable
regular file".

Thanks.