Fix cider-jack-in failing in remote ssh buffers (#3544)

* tramp-sample-project: fix Lein not finding `java` after cider-jack-in

This is a workaround that can be removed when `PATH` is picked up
correctly when jacking in on the running remote.

Circumvents:

```
Tramp: Opening connection nrepl-server for root@localhost using sshx...done
[nREPL] Starting server via lein update-in :dependencies conj \[nrepl/nrepl\ \"1.0.0\"\] -- update-in :plugins conj \[cider/cider-nrepl\ \"0.40.0\"\] -- repl :headless :host localhost
error in process sentinel: let: Could not start nREPL server: /usr/local/bin/lein: line 224: type: java: not found
Leiningen couldn't find 'java' executable, which is required.
Please either set JAVA_CMD or put java (>=1.6) in your $PATH (/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/bin:/usr/local/sbin).
 ("exited abnormally with code 1")
```

* tramp-sample-project: add `cider-jack-in` method to README

* Fix `cider-jack-in` failing with SSH remotes

Calling cider-jack-in from a tramp buffer on a ssh-remote would throw:
"error in process filter: Wrong type argument: stringp, nil"

This happens because nrepl--ssh-tunnel-connect is trying to infer the
hostname from the current filename: It string-matches
on (buffer-file-name) which returns nil in
the *cider-uninitialized-repl* buffer.

For the jack-in use-case, the local var nrepl-project-dir will
always be bound when connecting the client, so we can use
it as a fallback.

Fixes #3541

Author: caadr

CHANGELOG.md

@@ -14,6 +14,7 @@
 
 ### Bugs fixed
 
+- [#3541](https://github.com/clojure-emacs/cider/issues/3541): Fix `cider-jack-in` failing with SSH remotes.
 - [#3559](https://github.com/clojure-emacs/cider/issues/3559): Don't apply [dynamic syntax highlighting](https://docs.cider.mx/cider/config/syntax_highlighting.html) over buffers belonging to unrelated Sesman sessions.
 
 ## 1.9.0 (2023-10-24)

dev/tramp-sample-project/Dockerfile

@@ -36,6 +36,7 @@ COPY . /usr/src/app
 RUN lein deps
 
 RUN echo "export JAVA_HOME=${JAVA_HOME}" >> /root/.bashrc
+RUN echo "export JAVA_CMD=${JAVA_HOME}/bin/java" >> /root/.bashrc
 RUN echo "export LEIN_HOME=${LEIN_HOME}" >> /root/.bashrc
 RUN echo "export LEIN_JAVA_CMD=${LEIN_JAVA_CMD}" >> /root/.bashrc
 RUN echo "export LEIN_JVM_OPTS=${LEIN_JVM_OPTS}" >> /root/.bashrc

dev/tramp-sample-project/README.md

@@ -4,8 +4,15 @@ The Docker image exposes a SSH server.
 
 This way, for development purposes, we can SSH into it with TRAMP and exercise CIDER's TRAMP-related capabilities.
 
-To get started:
+## Some ways to get started:
 
+### `cider-jack-in` from a tramp buffer
+* `M-:` `(async-shell-command "make run")` to run the Docker image
+* `M-:` `(find-file "/sshx:root@localhost#8022:/usr/src/app/src/foo.clj")`
+* `M-x` `cider-jack-in`
+* Enter password: `cider`
+
+###  Manually create a remote repl and connect to it
 * In one terminal tab, run `make run` to run the Docker image
 * Once it's ready, from another tab, run `make ssh` and start a repl manually from there
   * The password is `cider`

nrepl-client.el

@@ -271,6 +271,12 @@ Discards it if it can be determined that the port is not active."
                           (shell-command-to-string (format "lsof -i:%s" port-number))))
           port-string)))))
 
+(defun nrepl--ssh-file-name-matches-host-p (file-name host)
+  "Return t, if FILE-NAME is a tramp-file-name on HOST via ssh."
+  (when (tramp-tramp-file-p file-name)
+    (with-parsed-tramp-file-name file-name v
+      (and (member v-method '("ssh" "sshx"))
+           (member host (list v-host (concat v-host "#" v-port)))))))
 
 ;;; Bencode
 
@@ -587,14 +593,12 @@ 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* ((current-buf (buffer-file-name))
-         (tramp-file-regexp "/ssh:\\(.+@\\)?\\(.+?\\)\\(:\\|#\\).+")
+  (let* ((file-name (or (buffer-file-name) nrepl-project-dir))
          (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)
+                      ((nrepl--ssh-file-name-matches-host-p file-name host) file-name)
                       ;; Otherwise, if HOST was provided, use it for connection.
                       (host (format "/ssh:%s:" host))
                       ;; Use default directory as fallback.

test/nrepl-client-tests.el

@@ -158,6 +158,27 @@
         (expect (match-string 1 msg)
                 :to-equal "nrepl.sock"))))
 
+(describe "nrepl--ssh-file-name-matches-host-p"
+  (it "works in the most basic case"
+    (expect (nrepl--ssh-file-name-matches-host-p "/ssh:host:~/test/" "host")
+            :to-be-truthy)
+    (expect (nrepl--ssh-file-name-matches-host-p "/ssh:host:~/test/" "other-host")
+            :to-be nil))
+  (it "understands non-standart ssh ports and distinguishes between them"
+    (expect (nrepl--ssh-file-name-matches-host-p
+             "/ssh:tester@host#8022:~/test/" "host#8022")
+            :to-be-truthy)
+    (expect (nrepl--ssh-file-name-matches-host-p
+             "/ssh:tester@host#8022:~/test/" "host#7777")
+            :to-be nil))
+  (it "works with tramps other ssh methods"
+    (expect (nrepl--ssh-file-name-matches-host-p
+             "/sshx:tester@host:~/test/" "host")
+            :to-be-truthy))
+  (it "can handle nil"
+    (expect (nrepl--ssh-file-name-matches-host-p nil nil)
+            :to-be nil)))
+
 (describe "nrepl-client-lifecycle"
   (it "start and stop nrepl client process"