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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org
Subject: Re: [PATCH] t7800: don't rely on reuse_worktree_file()
Date: Thu, 16 Jan 2020 22:08:22 +0100 (CET)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.2001162207220.46@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20200116181940.GA2945961@coredump.intra.peff.net>

Hi Peff,

On Thu, 16 Jan 2020, Jeff King wrote:

> A test in t7800 tries to make sure that when git-difftool runs an
> external tool that fails, it stops looking at files. Our fake failing
> tool prints the file name it was asked to diff before exiting non-zero,
> and then we confirm the output contains only that file.
>
> However, this subtly relies on our internal reuse_worktree_file().
> Because we're diffing between branches, the command run by difftool
> might see:
>
>   - the git-stored filename (e.g., "file"), if we decided that the
>     working tree contents were up-to-date with the object in the index
>     and HEAD, and we could reuse them
>
>   - a temporary filename (e.g. "/tmp/abc123_file") if we had to dump the
>     contents from the object database
>
> If the latter case happens, then the test fails, because it's expecting
> the string "file". I discovered this when debugging something unrelated
> with reuse_worktree_file(). I _thought_ it should be able to be
> triggered by a racy-git situation, but running:
>
>   ./t7800-difftool.sh --stress --run=2,13
>
> never seems to fail. However, by my reading of reuse_worktree_file(),
> this would probably always fail under Cygwin, because it sets
> NO_FAST_WORKING_DIRECTORY. At any rate, since reuse_worktree_file()
> is meant to be an optimization that may or may not trigger, our test
> should be robust either way.
>
> Instead of checking the filename, let's just make sure we got a single
> line of output (which would not be true if we continued after the first
> failure).
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---

The reasoning and the patch seem sound to me.

Thanks,
Dscho

>  t/t7800-difftool.sh | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
> index 6bac9ed180..29b92907e2 100755
> --- a/t/t7800-difftool.sh
> +++ b/t/t7800-difftool.sh
> @@ -125,15 +125,14 @@ test_expect_success 'difftool stops on error with --trust-exit-code' '
>  	test_when_finished "rm -f for-diff .git/fail-right-file" &&
>  	test_when_finished "git reset -- for-diff" &&
>  	write_script .git/fail-right-file <<-\EOF &&
> -	echo "$2"
> +	echo failed
>  	exit 1
>  	EOF
>  	>for-diff &&
>  	git add for-diff &&
> -	echo file >expect &&
>  	test_must_fail git difftool -y --trust-exit-code \
>  		--extcmd .git/fail-right-file branch >actual &&
> -	test_cmp expect actual
> +	test_line_count = 1 actual
>  '
>
>  test_expect_success 'difftool honors exit status if command not found' '
> --
> 2.25.0.318.gee4019ba55
>

  reply	other threads:[~2020-01-16 21:08 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16 18:19 [PATCH] t7800: don't rely on reuse_worktree_file() Jeff King
2020-01-16 21:08 ` Johannes Schindelin [this message]
2020-01-16 22:48 ` Junio C Hamano

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