Fix Tramp file name completion

* lisp/net/tramp.el (tramp-completion-handle-expand-file-name):
Reimplement.  It must also work for the non-Tramp case.

* test/lisp/net/tramp-tests.el
(tramp-test26-interactive-file-name-completion): Fix test.

2 files changed, 29 insertions, 5 deletions

diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index b75a1816fdb..36305dda496 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -2948,9 +2948,21 @@ not in completion mode."
 
 (defun tramp-completion-handle-expand-file-name (filename &optional directory)
   "Like `expand-file-name' for partial Tramp files."
-  (if (file-name-absolute-p filename)
-      filename
-    (concat (or directory default-directory "/") filename)))
+  ;; We need special handling only when a method is needed.  Then we
+  ;; check, whether DIRECTORY is "/method:" or "/[method/".
+  (let ((dir (or directory default-directory "/")))
+    (cond
+     ((file-name-absolute-p filename) filename)
+     ((and (eq tramp-syntax 'simplified)
+           (string-match-p (rx (regexp tramp-postfix-host-regexp) eos) dir))
+      (concat dir filename))
+     ((string-match-p
+       (rx bos (regexp tramp-prefix-regexp)
+           (? (regexp tramp-method-regexp) (regexp tramp-postfix-method-regexp))
+           eos)
+       dir)
+      (concat dir filename))
+     (t (tramp-run-real-handler #'expand-file-name (list filename directory))))))
 
 (defun tramp-completion-handle-file-exists-p (filename)
   "Like `file-exists-p' for partial Tramp files."
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index eea59843d47..a9f22369231 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -4695,7 +4695,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                               tramp-prefix-format
                               (substring-no-properties method 0 2))
                         unread-command-events
-                        (mapcar #'identity (concat test "\t\n"))
+                        (mapcar #'identity (concat test "\t\t\n"))
                         completions nil
                         result (read-file-name "Prompt: "))
                   (if (not (get-buffer "*Completions*"))
@@ -4708,6 +4708,12 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                           (concat tramp-prefix-format method-string)
                           result)))
                     (with-current-buffer "*Completions*"
+                      ;; We must remove leading `default-directory'.
+                      (goto-char (point-min))
+                      (let ((inhibit-read-only t))
+                        (while (re-search-forward "//" nil 'noerror)
+                          (delete-region (line-beginning-position) (point))))
+                      (goto-char (point-min))
                       (re-search-forward
                        (rx bol (1+ nonl) "possible completions:" eol))
                       (forward-line 1)
@@ -4729,7 +4735,7 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                               tramp-prefix-format method-string
                               (substring-no-properties host 0 2))
                         unread-command-events
-                        (mapcar #'identity (concat test "\t\n"))
+                        (mapcar #'identity (concat test "\t\t\n"))
                         completions nil
                         result (read-file-name "Prompt: "))
                   (if (not (get-buffer "*Completions*"))
@@ -4744,6 +4750,12 @@ This tests also `make-symbolic-link', `file-truename' and `add-name-to-file'."
                            ipv6-prefix host ipv6-postfix tramp-postfix-host-format)
                           result)))
                     (with-current-buffer "*Completions*"
+                      ;; We must remove leading `default-directory'.
+                      (goto-char (point-min))
+                      (let ((inhibit-read-only t))
+                        (while (re-search-forward "//" nil 'noerror)
+                          (delete-region (line-beginning-position) (point))))
+                      (goto-char (point-min))
                       (re-search-forward
                        (rx bol (1+ nonl) "possible completions:" eol))
                       (forward-line 1)