Re: [PATCH] test-lib.sh: have all tests pass under "-x", remove BASH_XTRACEFD

[Jeff King <peff@peff.net>]

On Mon, Nov 29, 2021 at 09:13:23PM +0100, Ævar Arnfjörð Bjarmason wrote:

> Once that's been removed we can dig deeper and see that we only have
> "BASH_XTRACEFD" due to an earlier attempt to work around the same
> issue. See d88785e424a (test-lib: set BASH_XTRACEFD automatically,
> 2016-05-11) and the 90c8a1db9d6 (test-lib: silence "-x" cleanup under
> bash, 2017-12-08) follow-up.
>
> I.e. we had redirection in "test_eval_" to get more relevant trace
> output under bash, which in turn was only needed because
> BASH_XTRACEFD=1 was set, which in turn was trying to work around test
> failures under "set -x".
> 
> It's better if our test suite works the same way on all shells, rather
> than getting a passing run under "bash", only to have it fail with
> "-x" under say "dash". As the deleted code shows this is much simpler
> to implement across our supported POSIX shells.

I'm mildly negative on dropping BASH_XTRACEFD. IMHO it is not worth the
maintenance headache to have to remain vigilant against any shell
function's stderr being examined, when there is single-line solution
that fixes everything. Yes, the cost of using bash is high on some
platforms, but "-x" is an optional feature (though I am sympathetic to
people who are _surprised_ when "-x" breaks things, because it really is
a subtle thing, and knowing "you should try using bash" is not
immediately obvious).

Some folks (like Gábor) disagree and have done the work so far to make
sure that we pass even with "-x". But it feels like this is committing
the whole project to that maintenance. I dunno.

-Peff