Subject: [PATCH] t4053: avoid race when killing background processes

From: "Phillip Wood via GitGitGadget" <[email-masked]>
Date: Thu, 10 Aug 2023 14:33:13 +0000

From: Phillip Wood <[email-masked]>

The test 'diff --no-index reads from pipes' starts a couple of
background processes that write to the pipes that are passed to "diff
--no-index". If the test passes then we expect these processes to exit
as all their output will have been read. However if the test fails
then we want to make sure they do not hang about on the users machine
and the test remembers they should be killed by calling

      test_when_finished  "! kill $!"

after each background process is created. Unfortunately there is a
race where test_when_finished may run before the background process
exits even when all its output has been read resulting in the kill
command succeeding which causes the test to fail. Fix this by ignoring
the exit status of the kill command. If the diff is successful we
could instead wait for the background process to exit and check their
status but that feels like it is testing the platform's printf
implementation rather than git's code.

Reported-by: Jeff King <[email-masked]>
Signed-off-by: Phillip Wood <[email-masked]>
---
    t4053: avoid race when killing background processes
    
    Thanks to Peff for reporting this. Junio - this fixes a regression
    introduced in the current cycle. It is fairly minor though so I'm not
    sure if you want to pick it up now or wait until 2.42.0 is out.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1571%2Fphillipwood%2Fdiff-no-index-pipes-fixes-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1571/phillipwood/diff-no-index-pipes-fixes-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1571

 t/t4053-diff-no-index.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/t/t4053-diff-no-index.sh b/t/t4053-diff-no-index.sh
index a28b9ff2434..1fb7d334620 100755
--- a/t/t4053-diff-no-index.sh
+++ b/t/t4053-diff-no-index.sh
@@ -248,11 +248,11 @@ test_expect_success PIPE,SYMLINKS 'diff --no-index reads from pipes' '
 	{
 		(test_write_lines a b c >old) &
 	} &&
-	test_when_finished "! kill $!" &&
+	test_when_finished "kill $! || :" &&
 	{
 		(test_write_lines a x c >new) &
 	} &&
-	test_when_finished "! kill $!" &&
+	test_when_finished "kill $! || :" &&
 
 	cat >expect <<-EOF &&
 	diff --git a/old b/new-link

base-commit: a82fb66fed250e16d3010c75404503bea3f0ab61
-- 
gitgitgadget