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From: Junio C Hamano <gitster@pobox.com>
To: Denton Liu <liu.denton@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Eric Sunshine <sunshine@sunshineco.com>,
	Johannes Sixt <j6t@kdbg.org>, SZEDER Gábor <szeder.dev@gmail.com>
Subject: Re: [PATCH v4 01/14] t: teach test_cmp_rev to accept ! for not-equals
Date: Sun, 10 Nov 2019 15:58:52 +0900
Message-ID: <xmqq8sookyj7.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20191108211909.GA80210@generichostname> (Denton Liu's message of "Fri, 8 Nov 2019 13:19:09 -0800")

Denton Liu <liu.denton@gmail.com> writes:

> Hi Junio,
>
> On Fri, Nov 08, 2019 at 09:49:02PM +0900, Junio C Hamano wrote:
>> Denton Liu <liu.denton@gmail.com> writes:
>>
>> >> >  		local r1 r2
>> >> >  		r1=$(git rev-parse --verify "$1") &&
>> >> >  		r2=$(git rev-parse --verify "$2") &&
>> >>
>> >> If either of the calls fail, the assignment itself would fail, and
>> >> the &&-cascade would stop without executing the if statment below.
>> >>
>> 	r1=$(git rev-parse --verify "$1") ||
>> 		error "'$1' does not name a valid object"
>> 	r2=$(git rev-parse --verify "$2") ||
>> 		error "'$2' does not name a valid object"
>> 	if ! test "$r1" $op "$r2"
>> 	then
>> 		... they do not compare the same ...
>> 	fi
>
> With your suggestion, we actually introduce subtle undesired behaviour.
> The `error` calls don't actually exit the function early. To make it
> work, we need to add && to the end of the `error` calls.

Not &&-at-the-end, but yes, we'd need some early return after
noticing a bad input from the caller.

You said earlier that one of the issues that motivated you to update
the helper was that this obvious typo

	r1=... r2= ... &&
	! test_rev_cmp "$r1" "$rr2"

would not be noticed.  For such a fix, I do not think it is
sufficient to tweak the return value from the test_rev_cmp
helper function if we allow callers to expect failure like so.

And for that reason, your "allow 'test_rev_cmp ! R1 R2' syntax" part
of the change makes quite a lot of sense.  That again allows the
callers to rely on failure return from test_rev_cmp as an error.

> I'm wondering why we want to do this, though. rev-parse should already
> output an error message on stderr in the case where the rev-parse fails.
>
> I guess the error message of "fatal: Needed a single revision" could
> probably be improved but that feels like an improvement that should be
> targeted to rev-parse.

Not really.  The callers of rev-parse plumbing should expect that
exact string, if they want to differenciate different errors from
the program.


	r1=$(git rev-parse --verify "$1") &&
	r2=$(git rev-parse --verify "$2") || return 1

before we start the comparison between $r1 and $r2 may be a good way
to clarify the intent of the code.  Using "&&" instead of "|| return"
and letting the whole function fail would not be incorrect, though.

Thanks.



  reply index

Thread overview: 116+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17 23:16 [PATCH 00/12] t5520: various test cleanup Denton Liu
2019-10-17 23:16 ` [PATCH 01/12] t5520: improve test style Denton Liu
2019-10-17 23:16 ` [PATCH 02/12] t5520: use sq for test case names Denton Liu
2019-10-17 23:17 ` [PATCH 03/12] t5520: let sed open its own input Denton Liu
2019-10-17 23:17 ` [PATCH 04/12] t5520: replace test -f with test_path_is_file Denton Liu
2019-10-17 23:26   ` Eric Sunshine
2019-10-17 23:35   ` [PATCH 4.5/12] t5520: replace test -f with test-lib functions Denton Liu
2019-10-18  0:11     ` Eric Sunshine
2019-10-17 23:17 ` [PATCH 05/12] t5520: remove spaces after redirect operator Denton Liu
2019-10-17 23:17 ` [PATCH 06/12] t5520: use test_line_count where possible Denton Liu
2019-10-17 23:17 ` [PATCH 07/12] t5520: replace test -{n,z} with test-lib functions Denton Liu
2019-10-17 23:31   ` Eric Sunshine
2019-10-17 23:17 ` [PATCH 08/12] t5520: use test_cmp_rev where possible Denton Liu
2019-10-17 23:41   ` Eric Sunshine
2019-10-18 18:52     ` Denton Liu
2019-10-23 13:53       ` Eric Sunshine
2019-10-17 23:17 ` [PATCH 09/12] t5520: test single-line files by git with test_cmp Denton Liu
2019-10-17 23:49   ` Eric Sunshine
2019-10-17 23:17 ` [PATCH 10/12] t5520: don't put git in upstream of pipe Denton Liu
2019-10-17 23:17 ` [PATCH 11/12] t5520: replace subshell cat comparison with test_cmp Denton Liu
2019-10-17 23:17 ` [PATCH 12/12] t5520: replace `! git` with `test_must_fail git` Denton Liu
2019-10-18 22:10 ` [PATCH v2 00/15] t5520: various test cleanup Denton Liu
2019-10-18 22:04   ` [PATCH v2 01/15] t7408: replace `test_must_fail test_path_is_file` Denton Liu
2019-10-19 11:58     ` Johannes Sixt
2019-10-18 22:04   ` [PATCH v2 09/15] t5520: replace test -{n,z} with test-lib functions Denton Liu
2019-10-18 22:04   ` [PATCH v2 11/15] t5520: test single-line files by git with test_cmp Denton Liu
2019-10-18 22:10   ` [PATCH v2 02/15] t: teach test_cmp_rev to accept ! for not-equals Denton Liu
2019-10-18 22:45     ` SZEDER Gábor
2019-10-18 22:10   ` [PATCH v2 03/15] t5520: improve test style Denton Liu
2019-10-18 22:10   ` [PATCH v2 04/15] t5520: use sq for test case names Denton Liu
2019-10-18 22:10   ` [PATCH v2 05/15] t5520: let sed open its own input Denton Liu
2019-10-18 22:10   ` [PATCH v2 06/15] t5520: replace test -f with test-lib functions Denton Liu
2019-10-18 22:10   ` [PATCH v2 07/15] t5520: remove spaces after redirect operator Denton Liu
2019-10-18 22:10   ` [PATCH v2 08/15] t5520: use test_line_count where possible Denton Liu
2019-10-18 22:10   ` [PATCH v2 10/15] t5520: use test_cmp_rev " Denton Liu
2019-10-18 22:10   ` [PATCH v2 12/15] t5520: don't put git in upstream of pipe Denton Liu
2019-10-18 22:10   ` [PATCH v2 13/15] t5520: replace subshell cat comparison with test_cmp Denton Liu
2019-10-18 22:10   ` [PATCH v2 14/15] t5520: remove redundant lines in test cases Denton Liu
2019-10-18 22:10   ` [PATCH v2 15/15] t5520: replace `! git` with `test_must_fail git` Denton Liu
2019-10-18 22:14   ` [PATCH v2 00/15] t5520: various test cleanup Denton Liu
2019-10-22 10:19   ` [PATCH v3 00/14] " Denton Liu
2019-10-22 10:19     ` [PATCH v3 01/14] t: teach test_cmp_rev to accept ! for not-equals Denton Liu
2019-10-22 10:19     ` [PATCH v3 02/14] t5520: improve test style Denton Liu
2019-10-22 10:19     ` [PATCH v3 03/14] t5520: use sq for test case names Denton Liu
2019-10-22 10:20     ` [PATCH v3 04/14] t5520: let sed open its own input Denton Liu
2019-10-22 10:20     ` [PATCH v3 05/14] t5520: replace test -f with test-lib functions Denton Liu
2019-10-22 10:20     ` [PATCH v3 06/14] t5520: remove spaces after redirect operator Denton Liu
2019-10-22 10:20     ` [PATCH v3 07/14] t5520: use test_line_count where possible Denton Liu
2019-10-22 10:20     ` [PATCH v3 08/14] t5520: replace test -{n,z} with test-lib functions Denton Liu
2019-10-22 10:20     ` [PATCH v3 09/14] t5520: use test_cmp_rev where possible Denton Liu
2019-10-22 10:20     ` [PATCH v3 10/14] t5520: test single-line files by git with test_cmp Denton Liu
2019-10-22 10:20     ` [PATCH v3 11/14] t5520: don't put git in upstream of pipe Denton Liu
2019-10-22 10:20     ` [PATCH v3 12/14] t5520: replace subshell cat comparison with test_cmp Denton Liu
2019-10-22 10:20     ` [PATCH v3 13/14] t5520: remove redundant lines in test cases Denton Liu
2019-10-22 10:20     ` [PATCH v3 14/14] t5520: replace `! git` with `test_must_fail git` Denton Liu
2019-10-24 23:21     ` [PATCH v3 00/14] t5520: various test cleanup Denton Liu
2019-10-25  3:44       ` Junio C Hamano
2019-11-04 19:17         ` Denton Liu
2019-11-06  2:37           ` Junio C Hamano
2019-11-07 18:51     ` [PATCH v4 " Denton Liu
2019-11-07 18:51       ` [PATCH v4 01/14] t: teach test_cmp_rev to accept ! for not-equals Denton Liu
2019-11-08  3:24         ` Junio C Hamano
2019-11-08  8:23           ` Denton Liu
2019-11-08 12:49             ` Junio C Hamano
2019-11-08 21:19               ` Denton Liu
2019-11-10  6:58                 ` Junio C Hamano [this message]
2019-11-07 18:51       ` [PATCH v4 02/14] t5520: improve test style Denton Liu
2019-11-07 18:51       ` [PATCH v4 03/14] t5520: use sq for test case names Denton Liu
2019-11-07 18:51       ` [PATCH v4 04/14] t5520: let sed open its own input Denton Liu
2019-11-07 18:51       ` [PATCH v4 05/14] t5520: replace test -f with test-lib functions Denton Liu
2019-11-07 18:51       ` [PATCH v4 06/14] t5520: remove spaces after redirect operator Denton Liu
2019-11-07 18:51       ` [PATCH v4 07/14] t5520: use test_line_count where possible Denton Liu
2019-11-07 18:51       ` [PATCH v4 08/14] t5520: replace test -{n,z} with test-lib functions Denton Liu
2019-11-07 18:51       ` [PATCH v4 09/14] t5520: use test_cmp_rev where possible Denton Liu
2019-11-07 18:51       ` [PATCH v4 10/14] t5520: test single-line files by git with test_cmp Denton Liu
2019-11-07 18:51       ` [PATCH v4 11/14] t5520: don't put git in upstream of pipe Denton Liu
2019-11-07 18:51       ` [PATCH v4 12/14] t5520: replace subshell cat comparison with test_cmp Denton Liu
2019-11-07 18:51       ` [PATCH v4 13/14] t5520: remove redundant lines in test cases Denton Liu
2019-11-07 18:51       ` [PATCH v4 14/14] t5520: replace `! git` with `test_must_fail git` Denton Liu
2019-11-12  0:13       ` [PATCH v5 00/14] t5520: various test cleanup Denton Liu
2019-11-12  0:13         ` [PATCH v5 01/14] t: teach test_cmp_rev to accept ! for not-equals Denton Liu
2019-11-12  6:52           ` Junio C Hamano
2019-11-12 19:38             ` [PATCH] fixup! " Denton Liu
2019-11-12  0:13         ` [PATCH v5 02/14] t5520: improve test style Denton Liu
2019-11-12  0:13         ` [PATCH v5 03/14] t5520: use sq for test case names Denton Liu
2019-11-12  0:13         ` [PATCH v5 04/14] t5520: let sed open its own input Denton Liu
2019-11-12  0:13         ` [PATCH v5 05/14] t5520: replace test -f with test-lib functions Denton Liu
2019-11-12  0:13         ` [PATCH v5 06/14] t5520: remove spaces after redirect operator Denton Liu
2019-11-12  0:13         ` [PATCH v5 07/14] t5520: use test_line_count where possible Denton Liu
2019-11-12  0:13         ` [PATCH v5 08/14] t5520: replace test -{n,z} with test-lib functions Denton Liu
2019-11-12  0:14         ` [PATCH v5 09/14] t5520: use test_cmp_rev where possible Denton Liu
2019-11-12  0:14         ` [PATCH v5 10/14] t5520: test single-line files by git with test_cmp Denton Liu
2019-11-12  5:17           ` Junio C Hamano
2019-11-12 23:06             ` Denton Liu
2019-11-12  0:14         ` [PATCH v5 11/14] t5520: don't put git in upstream of pipe Denton Liu
2019-11-12  0:14         ` [PATCH v5 12/14] t5520: replace subshell cat comparison with test_cmp Denton Liu
2019-11-12  0:14         ` [PATCH v5 13/14] t5520: remove redundant lines in test cases Denton Liu
2019-11-12  0:14         ` [PATCH v5 14/14] t5520: replace `! git` with `test_must_fail git` Denton Liu
2019-11-12 23:07         ` [PATCH v6 00/14] t5520: various test cleanup Denton Liu
2019-11-12 23:07           ` [PATCH v6 01/14] t: teach test_cmp_rev to accept ! for not-equals Denton Liu
2019-11-13  1:57             ` Junio C Hamano
2019-11-14  0:52               ` Denton Liu
2019-11-12 23:07           ` [PATCH v6 02/14] t5520: improve test style Denton Liu
2019-11-12 23:07           ` [PATCH v6 03/14] t5520: use sq for test case names Denton Liu
2019-11-12 23:07           ` [PATCH v6 04/14] t5520: let sed open its own input Denton Liu
2019-11-12 23:07           ` [PATCH v6 05/14] t5520: replace test -f with test-lib functions Denton Liu
2019-11-12 23:07           ` [PATCH v6 06/14] t5520: remove spaces after redirect operator Denton Liu
2019-11-12 23:08           ` [PATCH v6 07/14] t5520: use test_line_count where possible Denton Liu
2019-11-12 23:08           ` [PATCH v6 08/14] t5520: replace test -{n,z} with test-lib functions Denton Liu
2019-11-12 23:08           ` [PATCH v6 09/14] t5520: use test_cmp_rev where possible Denton Liu
2019-11-12 23:08           ` [PATCH v6 10/14] t5520: test single-line files by git with test_cmp Denton Liu
2019-11-12 23:08           ` [PATCH v6 11/14] t5520: don't put git in upstream of pipe Denton Liu
2019-11-12 23:08           ` [PATCH v6 12/14] t5520: replace $(cat ...) comparison with test_cmp Denton Liu
2019-11-12 23:08           ` [PATCH v6 13/14] t5520: remove redundant lines in test cases Denton Liu
2019-11-12 23:08           ` [PATCH v6 14/14] t5520: replace `! git` with `test_must_fail git` Denton Liu
2019-11-13  1:59           ` [PATCH v6 00/14] t5520: various test cleanup Junio C Hamano

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