[PATCH v2] generic/556: Filter touch error message

[Gabriel Krisman Bertazi <krisman@collabora.com>]

Coreutils commit d435cfc0bc55 ("touch: fix wrong
diagnostic (Bug#48106)"), released in coreutils v9.0, changed the error
reported by the tool when openat() fails with EINVAL.  Instead of
reporting a generic message for the failure of either openat() or the
following utimensat(), it now differentiates both failures with
different messages.

This change breaks generic/556, which relied on the parsing of that
message.  This test was originally developed by me on a Debian
Buster (coreutils v8.x), so I used the generic error message.  Now that
I tried to run it on a more modern distro, it reports a different error
message, which fails the test.

The patch filters out the touch-specific parts of the touch error
messages, to prevent breakage from future changes, but preserves the
return code information, which is actually useful (and more stable).

There is no change in behavior on the kernel side, just a broken test.
On both older and new distros, the kernel correctly rejects this invalid
sequence with -EINVAL, as shown in the strace hunk below:

...
openat(AT_FDCWD, "/scratch_mnt/strict/corac\314\247\303", ...) = -1 EINVAL
utimensat(AT_FDCWD, "/scratch_mnt/strict/corac\314\247\303", ...) = -1 EINVAL
...

Tested on Debian sid (coreutils v8.32) and Fedora (coreutils 9.0).

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

---
Changes since v1:
  - Dont break on older distros
---
 common/filter         | 8 ++++++++
 tests/generic/556     | 9 +++++++--
 tests/generic/556.out | 4 ++--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/common/filter b/common/filter
index 5b20e848c9b9..a6a42b7a6ad2 100644
--- a/common/filter
+++ b/common/filter
@@ -478,6 +478,14 @@ _filter_stat()
 	sed -e "s/\<cannot stat\>/cannot statx/"
 }
 
+# touch v9.0+ modified part of the message printed on error.  Filter the
+# generic part out, but preserve the strerror() part, which is
+# actually useful for debugging and usually stable.
+_filter_touch()
+{
+	sed -e "s/.* '\(.*\)':\(.*\)/touch: '\1':\2/"
+}
+
 _filter_lostfound()
 {
 	sed -e '/^lost+found$/d'
diff --git a/tests/generic/556 b/tests/generic/556
index 7ef2f6f4106b..1296e241552c 100755
--- a/tests/generic/556
+++ b/tests/generic/556
@@ -44,6 +44,11 @@ jp_file2=$(echo -e "japanese_\xe3\x82\xb1\xe3\x82\x99.txt")
 blob_file1=$(echo -e "corac\xcc\xa7\xc3")
 blob_file2=$(echo -e "coraç\xc3")
 
+filter_touch()
+{
+    _filter_touch | _filter_scratch
+}
+
 # Test helpers
 basic_create_lookup()
 {
@@ -456,8 +461,8 @@ test_strict_mode_invalid_filename()
 
 	# These creation commands should fail, since we are on strict
 	# mode.
-	touch "${basedir}/${blob_file1}" 2>&1 | _filter_scratch
-	touch "${basedir}/${blob_file2}" 2>&1 | _filter_scratch
+	touch "${basedir}/${blob_file1}" 2>&1 | filter_touch
+	touch "${basedir}/${blob_file2}" 2>&1 | filter_touch
 }
 
 #############
diff --git a/tests/generic/556.out b/tests/generic/556.out
index f9dd9542fb12..a689a3e2311c 100644
--- a/tests/generic/556.out
+++ b/tests/generic/556.out
@@ -12,5 +12,5 @@ user.foo="bar"
 # file: SCRATCH_MNT/xattrs/x/f1
 user.foo="bar"
 
-touch: setting times of 'SCRATCH_MNT/strict/corac'$'\314\247\303': Invalid argument
-touch: setting times of 'SCRATCH_MNT/strict/cora'$'\303\247\303': Invalid argument
+touch: 'SCRATCH_MNT/strict/corac'$'\314\247\303': Invalid argument
+touch: 'SCRATCH_MNT/strict/cora'$'\303\247\303': Invalid argument
-- 
2.36.1