Subject: [PATCH 2/3] add -p: gracefully ignore unparseable hunk headers in colored diffs

From: "Johannes Schindelin via GitGitGadget" <[email-masked]>
Date: Tue, 23 Aug 2022 18:04:29 +0000

From: Johannes Schindelin <[email-masked]>

In
https://lore.kernel.org/git/[email-masked],
Phillipe Blain reported that the built-in `git add -p` command fails
when asked to use [`diff-so-fancy`][diff-so-fancy] to colorize the diff.

The reason is that this tool produces colored diffs with a hunk header
that does not contain any parseable `@@ ... @@` line range information,
and therefore we cannot detect any part in that header that comes after
the line range.

Let's punt for now and simply show nothing apart from the line range in
that case.

[diff-so-fancy]: https://github.com/so-fancy/diff-so-fancy

Signed-off-by: Johannes Schindelin <[email-masked]>
---
 add-patch.c                | 15 ++++++---------
 t/t3701-add-interactive.sh |  9 +++++++++
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/add-patch.c b/add-patch.c
index 509ca04456b..f2fffe1af02 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -357,16 +357,13 @@ static int parse_hunk_header(struct add_p_state *s, struct hunk *hunk)
 	eol = memchr(line, '\n', s->colored.len - hunk->colored_start);
 	if (!eol)
 		eol = s->colored.buf + s->colored.len;
-	p = memmem(line, eol - line, "@@ -", 4);
-	if (!p)
-		return error(_("could not parse colored hunk header '%.*s'"),
-			     (int)(eol - line), line);
-	p = memmem(p + 4, eol - p - 4, " @@", 3);
-	if (!p)
-		return error(_("could not parse colored hunk header '%.*s'"),
-			     (int)(eol - line), line);
 	hunk->colored_start = eol - s->colored.buf + (*eol == '\n');
-	header->colored_extra_start = p + 3 - s->colored.buf;
+	p = memmem(line, eol - line, "@@ -", 4);
+	if (p && (p = memmem(p + 4, eol - p - 4, " @@", 3)))
+		header->colored_extra_start = p + 3 - s->colored.buf;
+	else
+		/* could not parse colored hunk header, showing nothing */
+		header->colored_extra_start = hunk->colored_start;
 	header->colored_extra_end = hunk->colored_start;
 
 	return 0;
diff --git a/t/t3701-add-interactive.sh b/t/t3701-add-interactive.sh
index b40d1c94d99..7e3c1de71f5 100755
--- a/t/t3701-add-interactive.sh
+++ b/t/t3701-add-interactive.sh
@@ -766,6 +766,15 @@ test_expect_success 'detect bogus diffFilter output' '
 	force_color test_must_fail git add -p <y
 '
 
+test_expect_success 'gracefully fail to parse colored hunk header' '
+	git reset --hard &&
+
+	echo content >test &&
+	test_config interactive.diffFilter "sed s/@@/XX/g" &&
+	printf y >y &&
+	force_color git add -p <y
+'
+
 test_expect_success 'diff.algorithm is passed to `git diff-files`' '
 	git reset --hard &&
 
-- 
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