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From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Đoàn Trần Công Danh" <congdanhqx@gmail.com>, git@vger.kernel.org
Subject: Re: [PATCH 6/6] t4124: fix test for non-compliance diff
Date: Fri, 20 Mar 2020 01:20:55 -0400	[thread overview]
Message-ID: <20200320052055.GA499858@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqqlfnwc5p0.fsf@gitster.c.googlers.com>

On Thu, Mar 19, 2020 at 03:58:51PM -0700, Junio C Hamano wrote:

> >> Workaround this problem by assuming `diff(1)` output is unified
> >> if we couldn't make anything from normal-diff format.
> 
> I do not mind working it around, but I am a bit disturbed by an
> uneven attitude towards POSIX noncompliance this series has.  If
> we were willing to break other people's "sed" that does not do BRE
> correctly, instead of using '[+]' trick to accomodate them while
> making sure that an implementation that does not use nonstandard
> extension and does only BRE, we should just similarly be writing
> such an implementation of noncompliant diff off as broken, yet we
> bend backwards over to make sure we can work with them here.
> 
> IOW, I do not have trouble changing the test so that it works with
> noncompliant "diff".  But then in the same series, I would prefer to
> see the existing test keeps working with a possibly noncompliant
> "sed" implementation that has been working well with the tests.

I don't think it's inconsistent. Real-world experience trumps standards.
We _know_ that there is a real-world diff that generates only unified
diffs, and it is not too hard to work around it. So we should do so.

A sed that uses ERE and requires backslash-escaping pluses is
theoretical at this point. POSIX forbids it, and I would guess that
working around it would be more than just the "[+]" we found, because
other patterns probably need it, too. But we won't know until we find
one to test on.

So I'm not entirely against "[+]" as a defensive measure. But I have a
slight preference to avoid it until we know it's needed, not because
it's hard to do once, but because I don't want to grow too many
defensive superstitions if we don't know they're warranted.

-Peff

  reply	other threads:[~2020-03-20  5:20 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19 14:00 [PATCH 0/6] fix test failure with busybox Đoàn Trần Công Danh
2020-03-19 14:00 ` [PATCH 1/6] t4061: use POSIX compliance regex(7) Đoàn Trần Công Danh
2020-03-19 15:53   ` Jeff King
2020-03-19 16:01     ` Eric Sunshine
2020-03-19 22:02       ` Junio C Hamano
2020-03-20  1:35         ` Danh Doan
2020-03-19 14:00 ` [PATCH 2/6] test-lib-functions: test_cmp: eval $GIT_TEST_CMP Đoàn Trần Công Danh
2020-03-19 16:02   ` Jeff King
2020-03-19 16:14     ` Eric Sunshine
2020-03-20  1:29     ` Danh Doan
2020-03-19 14:00 ` [PATCH 3/6] t5003: skip conversion test if unzip -a is unavailable Đoàn Trần Công Danh
2020-03-19 16:03   ` Jeff King
2020-03-20  0:39     ` Danh Doan
2020-03-20  5:32       ` Jeff King
2020-03-19 14:00 ` [PATCH 4/6] t5616: use rev-parse instead to get HEAD's object_id Đoàn Trần Công Danh
2020-03-19 16:07   ` Jeff King
2020-03-20  0:57     ` Danh Doan
2020-03-19 14:00 ` [PATCH 5/6] t7063: use POSIX find(1) syntax Đoàn Trần Công Danh
2020-03-19 16:12   ` Jeff King
2020-03-19 22:16     ` Junio C Hamano
2020-03-20  1:41       ` Danh Doan
2020-03-20  2:20         ` Danh Doan
2020-03-20  5:37         ` Jeff King
2020-03-22  0:37           ` Danh Doan
2020-03-22  6:05             ` Jeff King
2020-03-19 14:00 ` [PATCH 6/6] t4124: fix test for non-compliance diff Đoàn Trần Công Danh
2020-03-19 16:33   ` Jeff King
2020-03-19 22:58     ` Junio C Hamano
2020-03-20  5:20       ` Jeff King [this message]
2020-03-20  1:52     ` Danh Doan
2020-03-20  5:23       ` Jeff King
2020-03-19 15:51 ` [PATCH 0/6] fix test failure with busybox Jeff King
2020-03-20  0:37   ` Danh Doan
2020-03-20  5:30     ` Jeff King
2020-03-19 16:34 ` Jeff King

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