Re: [PATCH v2 4/5] tests: do not let lazy prereqs inside `test_expect_*` turn off tracing

[Jeff King <peff@peff.net>]

On Wed, Mar 25, 2020 at 05:41:20AM +0000, Johannes Schindelin via GitGitGadget wrote:

> From: Johannes Schindelin <johannes.schindelin@gmx.de>
> 
> The `test_expect_*` functions use `test_eval_` and so does
> `test_run_lazy_prereq_`. If tracing is enabled via the `-x` option,
> `test_eval_` turns on tracing while evaluating the code block, and turns
> it off directly after it.
> 
> This is unwanted for nested invocations.
> 
> One somewhat surprising example of this is when running a test that
> calls `test_i18ngrep`: that function requires the `C_LOCALE_OUTPUT`
> prereq, and that prereq is a lazy one, so it is evaluated via
> `test_eval_`, the command tracing is turned off, and the test case
> continues to run _without tracing the commands_.

Good catch. I didn't see this when looking at the GPG stuff earlier
because I didn't nest the lazy prereqs. But it is worth fixing
regardless, because as you note it comes up in other places.

> @@ -926,7 +927,8 @@ test_eval_ () {
>  		test_eval_ret_=$?
>  		if want_trace
>  		then
> -			set +x
> +			test 1 = $_trace_level && set +x
> +			_trace_level=$(($_trace_level-1))
>  		fi
>  	} 2>/dev/null 4>&2

I briefly wondered if adding more logic here might upset our delicate
balance of avoiding writing cruft to the "-x" output. But the answer is
"no", due to the descriptor hackery at the end of that {} block.

Of course, any test evaluating a lazy prereq already gets tons of cruft
anyway, because the outer level of tracing sees all of our internal
function calls checking the prereq and setting up the inner level of
tracing. But there's not much we can do about that.

-Peff