Fix file-name-case-insensitive-p on non-existent files

* src/fileio.c (Ffile_name_case_insensitive_p): If the file
doesn't exist, move up the filesystem tree until an existing
directory is found.  Then test that directory for
case-insensitivity.  (Bug#32246)

1 files changed, 15 insertions, 0 deletions

diff --git a/src/fileio.c b/src/fileio.c
index b92492c93a6..2dcfb73b0d5 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -2296,6 +2296,21 @@ The arg must be a string.  */)
   if (!NILP (handler))
     return call2 (handler, Qfile_name_case_insensitive_p, filename);
 
+  /* If the file doesn't exist, move up the filesystem tree until we
+     reach an existing directory or the root.  */
+  if (NILP (Ffile_exists_p (filename)))
+    {
+      filename = Ffile_name_directory (filename);
+      while (NILP (Ffile_exists_p (filename)))
+        {
+          Lisp_Object newname = expand_and_dir_to_file (filename);
+          /* Avoid infinite loop if the root is reported as non-existing
+             (impossible?).  */
+          if (!NILP (Fstring_equal (newname, filename)))
+            break;
+          filename = newname;
+        }
+    }
   filename = ENCODE_FILE (filename);
   return file_name_case_insensitive_p (SSDATA (filename)) ? Qt : Qnil;
 }