Subject: Re: [PATCH] t/lib-terminal: make TTY a lazy prerequisite

From: Junio C Hamano <[email-masked]>
Date: Fri, 14 Mar 2014 15:05:45 -0700

Jeff King <[email-masked]> writes:

> On Fri, Mar 14, 2014 at 02:47:14PM -0700, Junio C Hamano wrote:
>
>> > Something like the patch below (looks like we should be using $PERL_PATH
>> > instead of "perl", too).
>
> Actually, we don't need to do this, as of 94221d2 (t: use perl instead
> of "$PERL_PATH" where applicable, 2013-10-28). If only the author of
> that commit were here to correct me...

Yuck. I forgot all about that, too.

I wonder if that commit (actually the one before it) invites subtle
bugs by tempting us to say

	sane_unset VAR &&
	VAR=VAL perl -e 0 &&
        test "${VAR+isset}" != "isset"

> -- >8 --
> Subject: t/lib-terminal: make TTY a lazy prerequisite
>
> When lib-terminal.sh is sourced by a test script, we
> immediately set up the TTY prerequisite. We do so inside a
> test_expect_success, because that nicely isolates any
> generated output.
>
> However, this early test can interfere with a script that
> later wants to skip all tests (e.g., t5541 then goes on to
> set up the httpd server, and wants to skip_all if that
> fails). TAP output doesn't let us skip everything after we
> have already run at least one test.
>
> We could fix this by reordering the inclusion of
> lib-terminal.sh in t5541 to go after the httpd setup.  That
> solves this case, but we might eventually hit a case with
> circular dependencies, where either lib-*.sh include might
> want to skip_all after the other has run a test.  So
> instead, let's just remove the ordering constraint entirely
> by doing the setup inside a test_lazy_prereq construct,
> rather than in a regular test.  We never cared about the
> test outcome anyway (it was written to always succeed).
>
> Note that in addition to setting up the prerequisite, the
> current test also defines test_terminal. Since we can't
> affect the environment from a lazy_prereq, we have to hoist
> that out. We previously depended on it _not_ being defined
> when the TTY prereq isn't set as a way to ensure that tests
> properly declare their dependency on TTY. However, we still
> cover the case (see the in-code comment for details).
>
> Reported-by: Jens Lehmann <[email-masked]>
> Signed-off-by: Jeff King <[email-masked]>
> ---

Thanks.

>  t/lib-terminal.sh | 37 +++++++++++++++++++------------------
>  1 file changed, 19 insertions(+), 18 deletions(-)
>
> diff --git a/t/lib-terminal.sh b/t/lib-terminal.sh
> index 9a2dca5..5184549 100644
> --- a/t/lib-terminal.sh
> +++ b/t/lib-terminal.sh
> @@ -1,6 +1,20 @@
>  # Helpers for terminal output tests.
>  
> -test_expect_success PERL 'set up terminal for tests' '
> +# Catch tests which should depend on TTY but forgot to. There's no need
> +# to aditionally check that the TTY prereq is set here.  If the test declared
> +# it and we are running the test, then it must have been set.
> +test_terminal () {
> +	if ! test_declared_prereq TTY
> +	then
> +		echo >&4 "test_terminal: need to declare TTY prerequisite"
> +		return 127
> +	fi
> +	perl "$TEST_DIRECTORY"/test-terminal.perl "$@"
> +}
> +
> +test_lazy_prereq TTY '
> +	test_have_prereq PERL &&
> +
>  	# Reading from the pty master seems to get stuck _sometimes_
>  	# on Mac OS X 10.5.0, using Perl 5.10.0 or 5.8.9.
>  	#
> @@ -15,21 +29,8 @@ test_expect_success PERL 'set up terminal for tests' '
>  	# After 2000 iterations or so it hangs.
>  	# https://rt.cpan.org/Ticket/Display.html?id=65692
>  	#
> -	if test "$(uname -s)" = Darwin
> -	then
> -		:
> -	elif
> -		perl "$TEST_DIRECTORY"/test-terminal.perl \
> -			sh -c "test -t 1 && test -t 2"
> -	then
> -		test_set_prereq TTY &&
> -		test_terminal () {
> -			if ! test_declared_prereq TTY
> -			then
> -				echo >&4 "test_terminal: need to declare TTY prerequisite"
> -				return 127
> -			fi
> -			perl "$TEST_DIRECTORY"/test-terminal.perl "$@"
> -		}
> -	fi
> +	test "$(uname -s)" != Darwin &&
> +
> +	perl "$TEST_DIRECTORY"/test-terminal.perl \
> +		sh -c "test -t 1 && test -t 2"
>  '