[llvm] [lit] Cope with more cat variants (PR #121376)

[Angus Lees via llvm-commits]

https://github.com/anguslees created https://github.com/llvm/llvm-project/pull/121376

BusyBox `cat` has yet another slight variation of error formatting:

```console
$ cat --help 2>&1 | head -1
BusyBox v1.37.0 (2024-09-30 10:39:57 UTC) multi-call binary.

$ cat does-not-exist
cat: can't open 'does-not-exist': No such file or directory
```

Rather than extend the test result regex with a third case,
recognise that we only really care about the filename and errno string.
Weaken the regex to ignore all "noise" around the filename.

Note this also corrects what looks like a bug with the previous regex.
Previously, the `cannot open does-not-exist` alternate did not assert
the following errno message.  This was introduced in
https://reviews.llvm.org/D60553 (apparently) due to differences in the
`cat` command on AIX.  That bug doesn't include the specific
AIX output, so it's unclear if this omission was intended.

>From aafc0750f1ccc1cba1bc4ccdc24f777d664304c8 Mon Sep 17 00:00:00 2001
From: Angus Lees <gus at inodes.org>
Date: Tue, 31 Dec 2024 17:11:09 +1100
Subject: [PATCH] [lit] Cope with more cat variants

BusyBox `cat` has yet another slight variation of error formatting:

```console
$ cat --help 2>&1 | head -1
BusyBox v1.37.0 (2024-09-30 10:39:57 UTC) multi-call binary.

$ cat does-not-exist
cat: can't open 'does-not-exist': No such file or directory
```

Rather than extend the test result regex with a third case,
recognise that we only really care about the filename and errno string.
Weaken the regex to ignore all "noise" around the filename.

Note this also corrects what looks like a bug with the previous regex.
Previously, the `cannot open does-not-exist` alternate did not assert
the following errno message.  This was introduced in
https://reviews.llvm.org/D60553 (apparently) due to differences in the
`cat` command on AIX.  That bug doesn't include the specific
AIX output, so it's unclear if this omission was intended.
---
 llvm/utils/lit/tests/shtest-format.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/utils/lit/tests/shtest-format.py b/llvm/utils/lit/tests/shtest-format.py
index 3a1959549e5d01..d58973993b272a 100644
--- a/llvm/utils/lit/tests/shtest-format.py
+++ b/llvm/utils/lit/tests/shtest-format.py
@@ -18,7 +18,7 @@
 # CHECK: Command Output (stderr):
 # CHECK-NEXT: --
 # CHECK-NOT: --
-# CHECK: cat{{(_64)?(\.exe)?}}: {{cannot open does-not-exist|does-not-exist: No such file or directory}}
+# CHECK: cat{{(_64)?(\.exe)?}}: {{.*does-not-exist.*}}: No such file or directory
 # CHECK: --
 
 # CHECK: FAIL: shtest-format :: external_shell/fail_with_bad_encoding.txt