userdiff: skip textconv caching when not in a repository

Commit Message

Jeff King Feb. 26, 2024, 10:27 a.m. UTC

On Mon, Feb 26, 2024 at 08:56:09AM +0100, Paweł Dominiak wrote:

> But it seems like something git should handle on its own, so that diff
> would accommodate use in different circumstances with the same config.

Yes, definitely. Here's my patch with a commit message and a test.

-- >8 --
Subject: userdiff: skip textconv caching when not in a repository

The textconv caching system uses git-notes to store its cache entries.
But if you're using "diff --no-index" outside of a repository, then
obviously that isn't going to work.

Since caching is just an optimization, it's OK for us to skip it.
However, the current behavior is much worse: we call notes_cache_init()
which tries to look up the ref, and the low-level ref code hits a BUG(),
killing the program. Instead, we should notice before setting up the
cache that it there's no repository, and just silently skip it.

Reported-by: Paweł Dominiak <[e-mail]>
Signed-off-by: Jeff King <[e-mail]>
---
 t/t4042-diff-textconv-caching.sh | 22 ++++++++++++++++++++++
 userdiff.c                       |  4 +++-
 2 files changed, 25 insertions(+), 1 deletion(-)

Comments

Junio C Hamano Feb. 26, 2024, 4:35 p.m. UTC | #1

Jeff King <[e-mail]> writes:

> Subject: userdiff: skip textconv caching when not in a repository
>
> The textconv caching system uses git-notes to store its cache entries.
> But if you're using "diff --no-index" outside of a repository, then
> obviously that isn't going to work.
>
> Since caching is just an optimization, it's OK for us to skip it.
> However, the current behavior is much worse: we call notes_cache_init()
> which tries to look up the ref, and the low-level ref code hits a BUG(),
> killing the program. Instead, we should notice before setting up the
> cache that it there's no repository, and just silently skip it.

Makes sense.

Will queue.  Thanks.

Patch

diff --git a/t/t4042-diff-textconv-caching.sh b/t/t4042-diff-textconv-caching.sh
index bf33aedf4b..8ebfa3c1be 100755
--- a/t/t4042-diff-textconv-caching.sh
+++ b/t/t4042-diff-textconv-caching.sh
@@ -118,4 +118,26 @@  test_expect_success 'log notes cache and still use cache for -p' '
 	git log --no-walk -p refs/notes/textconv/magic HEAD
 '
 
+test_expect_success 'caching is silently ignored outside repo' '
+	mkdir -p non-repo &&
+	echo one >non-repo/one &&
+	echo two >non-repo/two &&
+	echo "* diff=test" >attr &&
+	test_expect_code 1 \
+	nongit git -c core.attributesFile="$PWD/attr" \
+		   -c diff.test.textconv="tr a-z A-Z <" \
+		   -c diff.test.cachetextconv=true \
+		   diff --no-index one two >actual &&
+	cat >expect <<-\EOF &&
+	diff --git a/one b/two
+	index 5626abf..f719efd 100644
+	--- a/one
+	+++ b/two
+	@@ -1 +1 @@
+	-ONE
+	+TWO
+	EOF
+	test_cmp expect actual
+'
+
 test_done
diff --git a/userdiff.c b/userdiff.c
index e399543823..fce3a31efa 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -3,6 +3,7 @@ 
 #include "userdiff.h"
 #include "attr.h"
 #include "strbuf.h"
+#include "environment.h"
 
 static struct userdiff_driver *drivers;
 static int ndrivers;
@@ -460,7 +461,8 @@  struct userdiff_driver *userdiff_get_textconv(struct repository *r,
 	if (!driver->textconv)
 		return NULL;
 
-	if (driver->textconv_want_cache && !driver->textconv_cache) {
+	if (driver->textconv_want_cache && !driver->textconv_cache &&
+	    have_git_dir()) {
 		struct notes_cache *c = xmalloc(sizeof(*c));
 		struct strbuf name = STRBUF_INIT;