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

On Mon, Nov 29, 2021 at 5:20 PM Ævar Arnfjörð Bjarmason
[off-list ref] wrote:

Change the "t1510-repo-setup.sh" test to use a new
"test_must_be_empty_trace" wrapper, instead of turning on
"test_untraceable=UnfortunatelyYes".

The only reason the test was incompatible with "-x" was because of
these "test_must_be_empty" checks, which we can instead instead skip
if we're running under "set -x".

s/instead instead/instead/

Skipping the tests is preferable to not having the "-x" output at all,
as it's much easier to debug the test. The result loss of test
coverage is minimal. If someone is adjusting a "test_must_be_empty"
test a failure might go away under "-x", but the new "say" we emit
here should highlight that appropriately.

Since the only user of "test_untraceable" is gone, we can remove that,
not only isn't it used now, but I think the rationale for using it in
the future no longer applies.

We'll be better off by using a simple wrapper like the new
"test_must_be_empty_trace". See 58275069288 (t1510-repo-setup: mark as
untraceable with '-x', 2018-02-24) and 5fc98e79fc0 (t: add means to
disable '-x' tracing for individual test scripts, 2018-02-24) for the
addition of "test_untraceable".

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.

Signed-off-by: Ævar Arnfjörð Bjarmason <redacted>