Making lsp work over tramp

[fakedrake]

I am not quite sure how obscure my case is but I had some trouble setting up lsp. I thought I would open this issue for posterity. The fundamental problem was two-fold: the rustic readme suggested using lsp-stdio-connection rather than lsp-tramp-connection when defining the remote server and that lsp itself is (probably) inconsistent w.r.t. when it uses executable-find and when it doesnt. The solution was to advise executable-find to return the same string it receives when the argument is a remote executable path:

(defun rustic-lsp-conn-command ()
  (cons
   (executable-find "rust-analyzer" t)
   (cl-rest lsp-rust-analyzer-server-args)))

(with-eval-after-load "lsp-rust"
  (defun start-file-process-shell-command@around (start-file-process-shell-command name buffer &rest args)
    "Start a program in a subprocess.  Return the process object
for it. Similar to `start-process-shell-command', but calls
`start-file-process'."
    ;; On remote hosts, the local `shell-file-name' might be useless.
    (let ((command (mapconcat 'identity args " ")))
      (funcall start-file-process-shell-command name buffer command)))

  (advice-add 'start-file-process-shell-command
              :around #'start-file-process-shell-command@around)

 (lsp-register-client
  (make-lsp-client
   :new-connection (lsp-tramp-connection #'rustic-lsp-conn-command)
   :remote? t
   :major-modes '(rust-mode rustic-mode)
   :initialization-options 'lsp-rust-analyzer--make-init-options
   :notification-handlers (ht<-alist lsp-rust-notification-handlers)
   :action-handlers (ht ("rust-analyzer.runSingle" #'lsp-rust--analyzer-run-single))
   :library-folders-fn (lambda (_workspace) lsp-rust-library-directories)
   :after-open-fn (lambda ()
                    (when lsp-rust-analyzer-server-display-inlay-hints
                      (lsp-rust-analyzer-inlay-hints-mode)))
   :ignore-messages nil
   :server-id 'rust-analyzer-remote)))


(defun expand-file-name-remote (file)
  "A tramp-friendly version of expand-file-name.  Expand file
relative to the remote part of default-directory."
  (let ((file (expand-file-name file))
        (dir-remote (file-remote-p default-directory)))
    (if (file-remote-p file)
        ;; if file is already remote, return it
        file
      ;; otherwise prepend the remote part (if any) of default-directory
      (concat dir-remote file))))

(defun around-ad-executable-find (orig-fn cmd &optional is-remote)
  (let ((remote-cmd (if is-remote (expand-file-name-remote cmd) cmd)))
    (if (file-executable-p remote-cmd)
        cmd
      (funcall orig-fn cmd is-remote))))
(advice-add 'executable-find :around 'around-ad-executable-find)

Please advise on whether there is something more official that we can do with this information (and if more of it is required)

[brotzeit]

I also didn't get this to work #337. But it seems it was working when the docs were added...

[brotzeit]

@yyoncho sorry for the ping, I know you're quite busy. Do you see anything obvious that we don't notice ?

[fakedrake]

Just to make sure that I am clear: with the above config lsp works (mostly) fine but it diverges a bit from the docs. Sometimes when the remote server dies the client is unable to restart it but I haven't been able to consistently reproduce it.

[buzmeg]

One thing I would like to flag is that you likely need to have something like this stashed somewhere:

(require 'tramp)
(add-to-list 'tramp-remote-path 'tramp-own-remote-path)

Otherwise, tramp completely blows away your path on the remote machine and finding rust-analyzer is unlikely to work.

Figuring this out caused me quite a lot of grief.

[brotzeit]

Unfortunately, lsp-mode doesn't seem to work with tramp. Hopefully somebody can fix this issue at some point. If you need to work with tramp the only option is eglot.

[cpoile]

Just wondering if there was any progress on this? I can confirm that the above code doesn't work for Emacs 29.1, and hoping maybe there was a new solution?

[bleggett]

(note: using DOOM emacs FWIW)

I have this:

(add-to-list 'tramp-remote-path 'tramp-own-remote-path)

and when I open a vterm shell in a tramp project, I can confirm that rust-analyzer is found in $PATH on the remote box - but rustic tries to find it from a location that doesn't exist on the remote box and doesn't seem to respect the remote $PATH when looking.