Emacs TRAMP

Emacs TRAMP is a method of running editing operations on a remote server.

Connecting To A Workspace

To connect to your workspace first run:

coder config-ssh

Then you can connect to your workspace by its name in the format: coder.<WORKSPACE NAME>.

In Emacs type C-x d and then input: /-:coder.<WORKSPACE NAME>: and hit enter. This will open up Dired on the workspace's home directory.

Using SSH

By default Emacs TRAMP is setup to use SCP to access files on the Coder workspace instance. However you might want to use SSH if you have a jumpbox or some other complex network setup.

To do so set the following in your Emacs init.el file:

(setq tramp-default-method "ssh")

Then when you access the workspace instance via /-:coder.<WORKSPACE NAME> Emacs will use SSH. Setting tramp-default-method will also tell ansi-term mode the correct way to access the remote when directory tracking.

Directory Tracking

ansi-term

If you run your terminal in Emacs via ansi-term then you might run into a problem where while SSH-ed into a workspace Emacs will not change its default-directory to open files in the directory your shell is in.

To fix this:

1. In your workspace Terraform template be sure to add the following:

   data "coder_workspace" "me" {
   }
   
   resource "coder_agent" "main" {
     # ...
     env = {
       name = "CODER_WORKSPACE_NAME"
       value = data.coder_workspace.me.name
     }
   }
   

2. Next in the shell profile file on the workspace (ex., ~/.bashrc for Bash and ~/.zshrc for Zsh) add the following:

   ansi_term_announce_host() {
       printf '\033AnSiTh %s\n' "coder.$CODER_WORKSPACE_NAME"
   }
   
   ansi_term_announce_user() {
       printf '\033AnSiTu %s\n' "$USER"
   }
   
   ansi_term_announce_pwd() {
       printf '\033AnSiTc %s\n' "$PWD"
   }
   
   ansi_term_announce() {
       ansi_term_announce_host
       ansi_term_announce_user
       ansi_term_announce_pwd
   }
   
   cd()    { command cd    "$@"; ansi_term_announce_pwd; }
   pushd() { command pushd "$@"; ansi_term_announce_pwd; }
   popd()  { command popd  "$@"; ansi_term_announce_pwd; }
   
   ansi_term_announce
   

   Ansi Term expects the terminal running inside of it to send escape codes to inform Emacs of the hostname, user, and working directory. The above code sends these escape codes and associated data whenever the terminal logs in and whenever the directory changes.

eshell

The eshell mode will perform directory tracking by default, no additional configuration is needed.

Language Servers (Code Completion)

If you use lsp-mode for code intelligence and completion some additional configuration is required.

In your Emacs init.el file you must register a LSP client and tell lsp-mode how to find it on the remote machine using the lsp-register-client function. For each LSP server you want to use in your workspace add the following:

(lsp-register-client (make-lsp-client :new-connection (lsp-tramp-connection "<LSP SERVER BINARY>")
              :major-modes '(<LANGUAGE MODE>)
              :remote? t
              :server-id '<LANGUAGE SERVER ID>))

This tells lsp-mode to look for a language server binary named <LSP SERVER BINARY> for use in <LANGUAGE MODE> on a machine named coder.<WORKSPACE NAME>. Be sure to replace the values between angle brackets:

• <LSP SERVER BINARY> : The name of the language server binary, without any path components. For example to use the Deno Javascript language server use the value deno.
• <LANGUAGE MODE>: The name of the Emacs major mode for which the language server should be used. For example to enable the language server for Javascript development use the value web-mode.
• <LANGUAGE SERVER ID>: This is just the name that lsp-mode will use to refer to this language server. If you are ever looking for output buffers or files they may have this name in them.

Calling the lsp-register-client function will tell lsp-mode the name of the LSP server binary. However this binary must be accessible via the path. If the language server binary is not in the path you must modify tramp-remote-path so that lsp-mode knows in what directories to look for the LSP server. To do this use TRAMP's connection profiles functionality. These connection profiles let you customize variables depending on what machine you are connected to. Add the following to your init.el:

(connection-local-set-profile-variables 'remote-path-lsp-servers
								 '((tramp-remote-path . ("<PATH TO ADD>" tramp-default-remote-path))))
(connection-local-set-profiles '(:machine "coder.<WORKSPACE NAME>") 'remote-path-lsp-servers)

The connection-local-set-profile-variables function creates a new connection profile by the name remote-path-lsp-servers. The connection-local-set-profiles then indicates this remote-path-lsp-servers connection profile should be used when connecting to a server named coder.<WORKSPACE NAME>. Be sure to replace <PATH TO ADD> with the directory in which a LSP server is present.

TRAMP and lsp-mode are fickle friends, sometimes there is weird behavior. If you find that language servers are hanging in the starting state then it might be helpful to set the lsp-log-io variable to t.

More details on configuring lsp-mode for TRAMP can be found in the lsp-mode documentation. The TRAMP tramp-remote-path documentation contains more examples and details of connection profiles.