Re: [PATCH v2] CodingGuidelines: explicitly allow "local" for test scripts

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: May 4, 2021, 12:27 UTC
Message-ID: <87czu6wuf3.fsf@evledraar.gmail.com>
In-Reply-To: <xmqqpmy76w31.fsf@gitster.g>

On Tue, May 04 2021, Junio C Hamano wrote:

Show 24 quoted lines

> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>> Is there any portability reason to avoid "local" in the porcelains? I
>> don't have any plans for using it, but I don't see why we'd explicitly
>> forbid it.
>
> Things that are not even in POSIX are forbidden unless explicitly
> allowed.
>
> In general, he way we encouraged people to think has been "don't use
> it, it is not even in POSIX" and "even if it is in POSIX, we know
> the support by platform/implementation X is broken, so let's not use
> it".  It has been successfully helped us to stay out of portability
> troubles.
>
> There may be a few tiny cases where we said "practically everybody
> we care about has it, even though it is not in POSIX, and it makes
> our life so vastly be better" to explicitly allow some feature,
> though.
>
> And "local"?  Not absolutely essential, unless you are doing a
> library that you want to avoid stepping on users' toes.  Besides, we
> are no longer adding scripted Porcelains left and right---rather,
> people are actively rewriting them.

[You mailed me off-list with "Did I forget to say it is not even POSIX?", I had this reply to that, also applicable here]:

BEGIN QUOTE

I'm aware that it's not in POSIX. What I'm getting at is that anyone who doesn't support this must have been failing t0000-basic.sh since 01d3a526ad9 (t0000: check whether the shell supports the "local" keyword, 2017-10-26), released with v2.16.0.

And all tests of any kind since 78dc08875cd (test-lib: allow short options to be bundled, 2020-03-22), perhaps earlier, I didn't trace the full includes, but that's the first use in test-lib.sh itself. Released with v2.27.0.

From my own cross-platform testing and us not having any reports about this I very much suspect that this is one of those not-in-POSIX but in practice supported everywhere, or at least anywhere Git has been ported to.

So just saying it's OK to use unconditionally of "in t/?" should be fine, like e.g. some of the C89-plus-XYZ features.

END QUOTE

Afterwards it occurred to me that your stance on in-tree *.sh goes against e.g. brian's opinion on it expressed in reply to [1], i.e. that we might justify future new *.sh built-ins.

In any case, as noted above I really don't care much about using "local" in any *.sh built-in. I just don't think this "We do not use it in scripted Porcelains[...]" clause is needed at all.

It's effectively synonymous with saying "we still want to support git on platforms that are so broken they can't even run a single test in our test suite".

1. https://lore.kernel.org/git/patch-1.1-83266f30b67-20210417T084346Z-avarab@gmail.com/