[Fix #2822] If current buffer is a TRAMP buffer, use its filename for SSH tunnel (#3264)

If current buffer is a TRAMP buffer, use its filename for SSH tunnel. This way, username and SSH port will be parsed from existing SSH connection, instead of using current username and default SSH port.

Also fixes #3261.

Author: OknoLombarda

CHANGELOG.md

@@ -13,6 +13,7 @@
 
 - Bump the injected nREPL version to 1.0.
 - [#3291](https://github.com/clojure-emacs/cider/pull/3291): **Remove** the `'cljs-pending` `repl-type`. It is replaced by `cider-repl-cljs-upgrade-pending`.
+- [#3261](https://github.com/clojure-emacs/cider/issues/3261): If user is connecting to nREPL from a TRAMP buffer, use its connection parameters (port, username) for establishing SSH tunnel.
 
 ### Bugs fixed
 

doc/modules/ROOT/pages/basics/up_and_running.adoc

@@ -262,7 +262,9 @@ config files such as `~/.ssh/config` and `~/.ssh/known_hosts`. This is known to
 cause problems with complex or nonstandard ssh configs.
 
 You can safely run `cider-jack-in-*` while working with remote files over TRAMP. CIDER
-will handle this use-case transparently for you.
+will reuse existing SSH connection's parameters (like port and username) for establishing SSH tunnel.
+The same will happen if you try to `cider-connect-*` to a host that matches the one you're currently
+connected to.
 
 == Connecting via unix domain file socket
 

nrepl-client.el

@@ -570,7 +570,18 @@ If NO-ERROR is non-nil, show messages instead of throwing an error."
 (defun nrepl--ssh-tunnel-connect (host port)
   "Connect to a remote machine identified by HOST and PORT through SSH tunnel."
   (message "[nREPL] Establishing SSH tunneled connection to %s:%s ..." host port)
-  (let* ((remote-dir (if host (format "/ssh:%s:" host) default-directory))
+  (let* ((current-buf (buffer-file-name))
+         (tramp-file-regexp "/ssh:\\(.+@\\)?\\(.+?\\)\\(:\\|#\\).+")
+         (remote-dir (cond
+                      ;; If current buffer is a TRAMP buffer and its host is
+                      ;; the same as HOST, reuse its connection parameters for
+                      ;; SSH tunnel.
+                      ((and (string-match tramp-file-regexp current-buf)
+                            (string= host (match-string 2 current-buf))) current-buf)
+                      ;; Otherwise, if HOST was provided, use it for connection.
+                      (host (format "/ssh:%s:" host))
+                      ;; Use default directory as fallback.
+                      (t default-directory)))
          (ssh (or (executable-find "ssh")
                   (error "[nREPL] Cannot locate 'ssh' executable")))
          (cmd (nrepl--ssh-tunnel-command ssh remote-dir port))
@@ -598,11 +609,12 @@ If NO-ERROR is non-nil, show messages instead of throwing an error."
     ;; forwarding is set up, which is used to synchronise on, so that
     ;; the port forwarding is up when we try to connect.
     (format-spec
-     "%s -v -N -L %p:localhost:%p %u'%h'"
+     "%s -v -N -L %p:localhost:%p %u'%h' %n"
      `((?s . ,ssh)
        (?p . ,port)
        (?h . ,v-host)
-       (?u . ,(if v-user (format "-l '%s' " v-user) ""))))))
+       (?u . ,(if v-user (format "-l '%s' " v-user) ""))
+       (?n . ,(if v-port (format "-p '%s' " v-port) ""))))))
 
 (autoload 'comint-watch-for-password-prompt "comint"  "(autoload).")