LSP doesn't start over Tramp

[Patryk27]

Hi,

rustic-mode works perfectly fine locally, but when started over a Tramp session (via standard C-x C-f /ssh:something), errors out with:

LSP :: There are no language servers supporting current mode `rustic-mode' registered with `lsp-mode'.
This issue might be caused by:
1. The language you are trying to use does not have built-in support in `lsp-mode'. You must install the required support manually. Examples of this are `lsp-java' or `lsp-metals'.
2. The language server that you expect to run is not configured to run for major mode `rustic-mode'. You may check that by checking the `:major-modes' that are passed to `lsp-register-client'.
3. `lsp-mode' doesn't have any integration for the language behind `rustic-mode'. Refer to https://emacs-lsp.github.io/lsp-mode/page/languages and https://langserver.org/ .

Syntax highlighting works, but LSP doesn't start at all.

For reference, I'm using standard Doom Emacs with no fancy plugins & no fancy configuration.

[brotzeit]

Is your LSP server installed on the remote system ?

[Patryk27]

Yes - I'm using NixOS, so my local & remote configuration are almost identical; additionally, LSP via ssh emacs -nw works as usual.

lsp-doctor via Tramp says:

Checking for Native JSON support: OK
Using company-capf: OK
Check emacs supports `read-process-output-max': OK
Check `read-process-output-max' default has been changed from 4k: OK
Byte compiled against Native JSON (recompile lsp-mode if failing when Native JSON available): OK
`gc-cons-threshold' increased?: OK
Using gccemacs with emacs lisp native compilation (https://akrl.sdf.org/gccemacs.html): NOT AVAILABLE (OPTIONAL)

[brotzeit]

I guess you are using rust-analyzer. Can you run it manually on the remote host ?

[Patryk27]

Yes, I'm using rust-analyzer - it works on the remote machine:

❯ rust-analyzer --version
rust-analyzer 2021-01-04

[brotzeit]

I haven't used lsp-mode on remote hosts, but I just noticed https://emacs-lsp.github.io/lsp-mode/page/remote/. Have you tried it ?

[Patryk27]

I've tried adding:

(with-eval-after-load "lsp-rust"
    (lsp-register-client
     (make-lsp-client
      :new-connection (lsp-tramp-connection
                       (executable-find (car lsp-rust-analyzer-server-command)))
      :major-modes '(rust-mode rustic-mode)
      :priority (if (eq lsp-rust-server 'rust-analyzer) 1 -1)
      :remote? t
      :initialization-options 'lsp-rust-analyzer--make-init-options
      :notification-handlers (ht<-alist lsp-rust-notification-handlers)
      :action-handlers (ht<-alist lsp-rust-action-handlers)
      :library-folders-fn (lambda (_workspace) lsp-rust-library-directories)
      :ignore-messages nil
      :server-id 'rust-analyzer-remote)))

(and similar ones)
... and they all made Emacs bail out with:

Debugger entered--Lisp error: (wrong-number-of-arguments (3 . 3) 7)
  start-file-process-shell-command("rust-analyzer-remote" "*rust-analyzer-remote*" "stty" "raw" ";" "/etc/profiles/per-user/ppp/bin/rust-analyzer" "2>/tmp/rust-analyzer-remote-3-stderr")
  apply(start-file-process-shell-command "rust-analyzer-remote" "*rust-analyzer-remote*" ("stty" "raw" ";" "/etc/profiles/per-user/ppp/bin/rust-analyzer" "2>/tmp/rust-analyzer-remote-3-stderr"))
  lsp--start-workspace(...)
  lsp--start-connection(...)
  mapcar(...)
  lsp--ensure-lsp-servers(...)
  lsp--try-project-root-workspaces(nil nil)
  lsp()
  rustic-setup-lsp()
  rustic-mode()

[Patryk27]

Actually, this new error might be emacs-lsp/lsp-mode#2514 - I'll check when I get home later.

[Patryk27]

Yeah, adding emacs-lsp/lsp-mode#2514 (comment) and #217 (comment) made LSP work 😄

Thanks for helping!

[brotzeit]

What did you do exactly so we can add it to the readme ?

[Patryk27]

I added those lines to my config.el:

;; fix for Emacs 28 (https://github.com/emacs-lsp/lsp-mode/issues/2514#issuecomment-759452037)
(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'."
    (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)

;; remote rust-analyzer
(with-eval-after-load "lsp-rust"
    (lsp-register-client
     (make-lsp-client
      :new-connection (lsp-tramp-connection
                       (executable-find (car lsp-rust-analyzer-server-command)))
      :major-modes '(rust-mode rustic-mode)
      :priority (if (eq lsp-rust-server 'rust-analyzer) 1 -1)
      :remote? t
      :initialization-options 'lsp-rust-analyzer--make-init-options
      :notification-handlers (ht<-alist lsp-rust-notification-handlers)
      :action-handlers (ht<-alist lsp-rust-action-handlers)
      :library-folders-fn (lambda (_workspace) lsp-rust-library-directories)
      :ignore-messages nil
      :server-id 'rust-analyzer-remote)))

[brotzeit]

Do you want to add a section to the readme ? I haven't set it up myself, so maybe you can add some hints why this is needed.

[Patryk27]

Sure, I'll prepare a merge request tomorrow :-)

[brotzeit]

Great, thanks!