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tests: replace chainlint subshell with a function

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To test that we don't break the &&-chain, test-lib.sh does something
like:

   (exit 117) && $test_commands

and checks that the result is exit code 117. We don't care what that
initial command is, as long as it exits with a unique code. Using "exit"
works and is simple, but is a bit expensive since it requires a subshell
(to avoid exiting the whole script!). This isn't usually very
noticeable, but it can add up for scripts which have a large number of
tests.

Using "return" naively won't work here, because we'd return from the
function eval-ing the snippet (and it wouldn't find &&-chain breakages).
But if we further push that into its own function, it does exactly what
we want, without extra subshell overhead.

According to hyperfine, this produces a measurable improvement when
running t3070 (which has 1800 tests, all of them quite short):

  'HEAD' ran
    1.09 ± 0.01 times faster than 'HEAD~1'

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2023-03-30 15:27:49 -04:00 committed by Junio C Hamano
parent 7b6555ab8d
commit 1686de55fa
1 changed files with 5 additions and 1 deletions
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6
t/test-lib.sh
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@ -1086,6 +1086,10 @@ test_eval_ () {
return $test_eval_ret_
}
fail_117 () {
return 117
}
test_run_ () {
test_cleanup=:
expecting_failure=$2
@ -1097,7 +1101,7 @@ test_run_ () {
trace=
# 117 is magic because it is unlikely to match the exit
# code of other programs
if test "OK-117" != "$(test_eval_ "(exit 117) && $1${LF}${LF}echo OK-\$?" 3>&1)"
if test "OK-117" != "$(test_eval_ "fail_117 && $1${LF}${LF}echo OK-\$?" 3>&1)"
then
BUG "broken &&-chain or run-away HERE-DOC: $1"
fi