[PATCH] test-lib: don't check prereqs of test cases that won't be run anyway

With './t1234-foo.sh -r 5,6' we can run only specific test cases in a
test script, but our test framwork still evaluates all lazy prereqs
that the excluded test cases might depend on.  This is unnecessary and
produces verbose and trace output that can be distracting.  This has
been an issue ever since the '-r|--run=' options were introduced in
0445e6f0a1 (test-lib: '--run' to run only specific tests, 2014-04-30),
because that commit added the check of the list of test cases
specified with '-r' after evaluating the prereqs.

Avoid this unnecessary prereq evaluation by checking the list of test
cases specified with '-r' before looking at the prereqs.

Note that GIT_SKIP_TESTS has always been checked before the prereqs,
so prereqs necessary for tests skipped that way were not evaluated.

Signed-off-by: SZEDER Gábor <redacted>
---

Following up on:

  https://public-inbox.org/git/20190923165828.GA27068@szeder.dev/

 t/test-lib.sh | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/t/test-lib.sh b/t/test-lib.sh
index e06fa02a0e..24b541f494 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh

@@ -1000,6 +1000,12 @@ test_skip () {
 		to_skip=t
 		skipped_reason="GIT_SKIP_TESTS"
 	fi
+	if test -z "$to_skip" && test -n "$run_list" &&
+	   ! match_test_selector_list '--run' $test_count "$run_list"
+	then
+		to_skip=t
+		skipped_reason="--run"
+	fi
 	if test -z "$to_skip" && test -n "$test_prereq" &&
 	   ! test_have_prereq "$test_prereq"
 	then

@@ -1012,12 +1018,6 @@ test_skip () {
 		fi
 		skipped_reason="missing $missing_prereq${of_prereq}"
 	fi
-	if test -z "$to_skip" && test -n "$run_list" &&
-		! match_test_selector_list '--run' $test_count "$run_list"
-	then
-		to_skip=t
-		skipped_reason="--run"
-	fi
 
 	case "$to_skip" in
 	t)

-- 
2.24.0.388.gde53c094ea

On Tue, Nov 12, 2019 at 01:24:38PM +0100, SZEDER Gábor wrote:

With './t1234-foo.sh -r 5,6' we can run only specific test cases in a
test script, but our test framwork still evaluates all lazy prereqs
that the excluded test cases might depend on.  This is unnecessary and
produces verbose and trace output that can be distracting.  This has
been an issue ever since the '-r|--run=' options were introduced in
0445e6f0a1 (test-lib: '--run' to run only specific tests, 2014-04-30),
because that commit added the check of the list of test cases
specified with '-r' after evaluating the prereqs.

Avoid this unnecessary prereq evaluation by checking the list of test
cases specified with '-r' before looking at the prereqs.

Note that GIT_SKIP_TESTS has always been checked before the prereqs,
so prereqs necessary for tests skipped that way were not evaluated.

Thanks. This definitely seems like an improvement. I verified that it
works in practice, and the patch itself looks obviously correct.

One of the things I had to double check is how to_skip is handled, since
we check it in the moved block. It's fine, but I wondered if the whole
thing would be easier as an if/else cascade with an early return. Like
the patch below (on top of your patch; try "diff -w" to quiet the
indentation noise).

But maybe it's not worth the churn (and if we pursue it at all, it
should not hold up your patch).

-Peff

diff --git a/t/test-lib.sh b/t/test-lib.sh
index 24b541f494..a1784114cb 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh

@@ -993,49 +993,38 @@ test_finish_ () {
 }
 
 test_skip () {
-	to_skip=
 	skipped_reason=
 	if match_pattern_list $this_test.$test_count $GIT_SKIP_TESTS
 	then
-		to_skip=t
 		skipped_reason="GIT_SKIP_TESTS"
-	fi
-	if test -z "$to_skip" && test -n "$run_list" &&
+	elif test -n "$run_list" &&
 	   ! match_test_selector_list '--run' $test_count "$run_list"
 	then
-		to_skip=t
 		skipped_reason="--run"
-	fi
-	if test -z "$to_skip" && test -n "$test_prereq" &&
+	elif
+	if test -n "$test_prereq" &&
 	   ! test_have_prereq "$test_prereq"
 	then
-		to_skip=t
-
 		of_prereq=
 		if test "$missing_prereq" != "$test_prereq"
 		then
 			of_prereq=" of $test_prereq"
 		fi
 		skipped_reason="missing $missing_prereq${of_prereq}"
+	else
+		return 1
 	fi
 
-	case "$to_skip" in
-	t)
-		if test -n "$write_junit_xml"
-		then
-			message="$(xml_attr_encode "$skipped_reason")"
-			write_junit_xml_testcase "$1" \
-				"      <skipped message=\"$message\" />"
-		fi
+	if test -n "$write_junit_xml"
+	then
+		message="$(xml_attr_encode "$skipped_reason")"
+		write_junit_xml_testcase "$1" \
+			"      <skipped message=\"$message\" />"
+	fi
 
-		say_color skip >&3 "skipping test: $@"
-		say_color skip "ok $test_count # skip $1 ($skipped_reason)"
-		: true
-		;;
-	*)
-		false
-		;;
-	esac
+	say_color skip >&3 "skipping test: $@"
+	say_color skip "ok $test_count # skip $1 ($skipped_reason)"
+	return 0
 }
 
 # stub; perf-lib overrides it

Hi Gábor,

On Tue, 12 Nov 2019, SZEDER Gábor wrote:

With './t1234-foo.sh -r 5,6' we can run only specific test cases in a
test script, but our test framwork still evaluates all lazy prereqs
that the excluded test cases might depend on.  This is unnecessary and
produces verbose and trace output that can be distracting.  This has
been an issue ever since the '-r|--run=' options were introduced in
0445e6f0a1 (test-lib: '--run' to run only specific tests, 2014-04-30),
because that commit added the check of the list of test cases
specified with '-r' after evaluating the prereqs.

Avoid this unnecessary prereq evaluation by checking the list of test
cases specified with '-r' before looking at the prereqs.

Note that GIT_SKIP_TESTS has always been checked before the prereqs,
so prereqs necessary for tests skipped that way were not evaluated.

Signed-off-by: SZEDER Gábor <redacted>
---

Thank you for this patch!
Dscho