[Emacs-diffs] master 8b13ec1: Fix expand-file-name for names starting with '~'

[Ken Brown]

branch: master
commit 8b13ec1d7022b05ce71982c83f320d5272b92de7
Author: Ken Brown <address@hidden>
Commit: Ken Brown <address@hidden>

    Fix expand-file-name for names starting with '~'
    
    * src/fileio.c: (file_name_absolute_no_tilde_p):
    New static function.
    (Fexpand_file_name): If the current buffer's default-directory
    starts with "~user" where "user" is not a valid user name, don't
    give the '~' a special meaning.  Just treat the value of
    default-directory as a relative name.  (Bug#36502)
    * test/src/fileio-tests.el
    (fileio-tests--relative-default-directory): Add a test.
---
 src/fileio.c             | 68 +++++++++++++++++++++++++++++++-----------------
 test/src/fileio-tests.el |  6 ++++-
 2 files changed, 49 insertions(+), 25 deletions(-)

diff --git a/src/fileio.c b/src/fileio.c
index 7f83267..4c7625c 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -737,6 +737,13 @@ For that reason, you should normally use `make-temp-file' 
instead.  */)
                                   empty_unibyte_string, Qnil);
 }
 
+/* NAME must be a string.  */
+static bool
+file_name_absolute_no_tilde_p (Lisp_Object name)
+{
+  return IS_ABSOLUTE_FILE_NAME (SSDATA (name));
+}
+
 DEFUN ("expand-file-name", Fexpand_file_name, Sexpand_file_name, 1, 2, 0,
        doc: /* Convert filename NAME to absolute, and canonicalize it.
 Second arg DEFAULT-DIRECTORY is directory to start with if NAME is relative
@@ -807,41 +814,54 @@ the root directory.  */)
       error ("Invalid handler in `file-name-handler-alist'");
     }
 
+  /* As a last resort, we may have to use the root as
+     default_directory below.  */
+  Lisp_Object root;
+#ifdef DOS_NT
+      /* "/" is not considered a root directory on DOS_NT, so using it
+        as default_directory causes an infinite recursion in, e.g.,
+        the following:
+
+            (let (default-directory)
+             (expand-file-name "a"))
+
+        To avoid this, we use the root of the current drive.  */
+      root = build_string (emacs_root_dir ());
+#else
+      root = build_string ("/");
+#endif
 
   /* Use the buffer's default-directory if DEFAULT_DIRECTORY is omitted.  */
   if (NILP (default_directory))
     {
       Lisp_Object dir = BVAR (current_buffer, directory);
-      /* The buffer's default-directory should be absolute.  If it
-        isn't, try to expand it relative to invocation-directory.
-        But we have to be careful to avoid an infinite loop, because
-        the code in emacs.c that sets Vinvocation_directory might
-        call Fexpand_file_name.  */
+      /* The buffer's default-directory should be absolute or should
+        start with `~'.  If it isn't absolute, we replace it by its
+        expansion relative to a known absolute name ABSDIR, which is
+        the invocation-directory if the latter is absolute, or the
+        root otherwise.
+
+        In case default-directory starts with `~' or `~user', where
+        USER is a valid user name, this correctly expands it (and
+        ABSDIR plays no role).  If USER is not a valid user name, the
+        leading `~' loses its special meaning and is retained as part
+        of the expanded name.  */
       if (STRINGP (dir))
        {
-         if (!NILP (Ffile_name_absolute_p (dir)))
+         if (file_name_absolute_no_tilde_p (dir))
            default_directory = dir;
-         else if (STRINGP (Vinvocation_directory)
-                  && !NILP (Ffile_name_absolute_p (Vinvocation_directory)))
-           default_directory = Fexpand_file_name (dir, Vinvocation_directory);
+         else
+           {
+             Lisp_Object absdir
+               = STRINGP (Vinvocation_directory)
+               && file_name_absolute_no_tilde_p (Vinvocation_directory)
+               ? Vinvocation_directory : root;
+             default_directory = Fexpand_file_name (dir, absdir);
+           }
        }
     }
   if (! STRINGP (default_directory))
-    {
-#ifdef DOS_NT
-      /* "/" is not considered a root directory on DOS_NT, so using "/"
-        here causes an infinite recursion in, e.g., the following:
-
-            (let (default-directory)
-             (expand-file-name "a"))
-
-        To avoid this, we set default_directory to the root of the
-        current drive.  */
-      default_directory = build_string (emacs_root_dir ());
-#else
-      default_directory = build_string ("/");
-#endif
-    }
+    default_directory = root;
 
   handler = Ffind_file_name_handler (default_directory, Qexpand_file_name);
   if (!NILP (handler))
diff --git a/test/src/fileio-tests.el b/test/src/fileio-tests.el
index 0e0230a..813ee5f 100644
--- a/test/src/fileio-tests.el
+++ b/test/src/fileio-tests.el
@@ -131,4 +131,8 @@ Also check that an encoding error can appear in a symlink."
 (ert-deftest fileio-tests--relative-default-directory ()
   "Test expand-file-name when default-directory is relative."
   (let ((default-directory "some/relative/name"))
-    (should (file-name-absolute-p (expand-file-name "foo")))))
+    (should (file-name-absolute-p (expand-file-name "foo"))))
+  (let* ((default-directory "~foo")
+         (name (expand-file-name "bar")))
+    (should (and (file-name-absolute-p name)
+                 (not (eq (aref name 0) ?~))))))