Re: [PATCH] test-lib.sh: use GIT_TEST_COLUMNS over COLUMNS

From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: git@vger.kernel.org, "Junio C Hamano" <gitster@pobox.com>,
	"Alex Henrie" <alexhenrie24@gmail.com>,
	"Felipe Contreras" <felipe.contreras@gmail.com>,
	"Fabian Stelzer" <fabian.stelzer@campoint.net>,
	"Zbigniew Jędrzejewski-Szmek" <zbyszek@in.waw.pl>
Subject: Re: [PATCH] test-lib.sh: use GIT_TEST_COLUMNS over COLUMNS
Date: Tue, 27 Jul 2021 13:38:14 -0400	[thread overview]
Message-ID: <YQBEhj/Y6m0pqOth@coredump.intra.peff.net> (raw)
In-Reply-To: <patch-1.1-f81f3911d5-20210726T235452Z-avarab@gmail.com>

On Tue, Jul 27, 2021 at 01:57:09AM +0200, Ævar Arnfjörð Bjarmason wrote:

> In my c49a177beca (test-lib.sh: set COLUMNS=80 for --verbose
> repeatability, 2021-06-29) the test suite started breaking on recent
> versions of bash.
> 
> This is because it sets "shopt -s checkwinsize" starting with version
> 5.0, furthermore it started setting COLUMNS under "shopt -s
> checkwinsize" for non-interactive use around version 4.3.
> 
> A narrow fix for that issue would be to add this just above our
> setting of COLUMNS in test-lib.sh:
> 
> 	shopt -u checkwinsize >/dev/null 2>&1
> 
> But we'd then be at the mercy of the next shell or terminal that wants
> to be clever about COLUMNS.
> 
> Let's instead solve this more thoroughly. We'll now take
> GIT_TEST_COLUMNS over COLUMNS, and furthermore intentionally spoil the
> COLUMNS variable to break any tests that rely on it being set to a
> sane value.
> 
> If something breaks because we have a codepath that's not
> term_columns() checking COLUMNS we'd like to know about it, the narrow
> "shopt -u checkwinsize" fix won't give us that.

I guess people running with bash won't see the test breakage (because
bash will quietly "fix" the COLUMNS setting). But enough people run with
/bin/sh that we'll eventually notice.

> This approach does mean that any tests of ours that expected to test
> term_columns() behavior by setting COLUMNS will need to explicitly
> unset GIT_TEST_COLUMNS, or set it to the empty string. I'm doing the
> latter in all the tests changed here.

This is rather ugly, and I'm not in general a fan of adding more
test-only code into the bowels of Git itself. But it may be the least
bad solution.

The only alternative I could come up with is _not_ to set COLUMNS
everywhere, but instead insist on each individual test manually doing
"COLUMNS=80 git ...". Setting it as a one-shot seems to be reliable
enough. The downside is just that various tests will need to do so. We
already have quite a few that do, but I guess anything that uses the
progress meter is now subject to it.

-Peff