Subject: bug#65356: 30.0.50; [wishlist] Support Tramp method, user name and host name completion in eshell

From: Michael Albinus <[email-masked]>
Date: Thu, 17 Aug 2023 20:01:51 +0200

When we open a file with find-file, the minibuffer offers method, user
name and host name completion for remote files. That is, after typing
"C-x C-f /ss TAB" we're offered with the completions "ssh:", "sshfs:"
and "sshx:". Same for user name and host name.

In eshell, this feature does not exist. I would like if I could type
"cd /ss TAB" and could see the same offering of "ssh:", "sshfs:" and
"sshx:". Same for user name and host name.

The appended patch does this for me. I have no idea how good it fits
into the eshell machinery, for example whether there are problems with
the em-elecslash.el module. Comments welcome!

Disclaimer: The idea has appeared on
<https://emacs.stackexchange.com/questions/78479/can-eshell-provide-tramp-auto-completion>.

Best regards, Michael.

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.38, cairo version 1.17.8) of 2023-08-15 built on gandalf
Repository revision: 5c101b1adac2b4f3cc4e08a6492b406952c529f3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12201009
System Description: Fedora Linux 38 (Workstation Edition)

Configured using:
 'configure --with-tree-sitter'

Configured features:
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LIBOTF LIBSELINUX LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY PDUMPER PNG
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diff --git a/lisp/eshell/em-tramp.el b/lisp/eshell/em-tramp.el
index 94eb9797033..c90e689f6de 100644
--- a/lisp/eshell/em-tramp.el
+++ b/lisp/eshell/em-tramp.el
@@ -51,11 +51,23 @@ eshell-tramp-initialize
   "Initialize the Tramp-using commands code."
   (when (eshell-using-module 'eshell-cmpl)
     (add-hook 'pcomplete-try-first-hook
-	      'eshell-complete-host-reference nil t))
+              'eshell-complete-partial-tramp-file-name))
   (setq-local eshell-complex-commands
               (append '("su" "sudo" "doas")
                       eshell-complex-commands)))

+(defun eshell-complete-partial-tramp-file-name ()
+  "Complete a partial Tramp file name (method, user name, hostname)."
+  (let ((arg (pcomplete-actual-arg))
+        (non-essential t)
+        (minibuffer-completing-file-name t))
+    (when (string-match tramp-completion-file-name-regexp arg)
+      (setq pcomplete-stub (substring arg (length tramp-prefix-format))
+            pcomplete-last-completion-raw t
+            pcomplete-termination-string "")
+      (throw 'pcomplete-completions
+             (file-name-all-completions pcomplete-stub tramp-prefix-format)))))
+
 (autoload 'eshell-parse-command "esh-cmd")

 (defun eshell/su (&rest args)