Allow connecting to nbb via connect-clj (clojure-emacs#3061)

This is for nbb, scittle, joyride.
Better support for "pain" repls, support "cljs" without setup.

we want to

1. connect with a plain client
2. make any assumptions explicit
3. connect cljs buffers with those plain repls

1. Check for cider middleware being present, before using it
(already being done)
2. Check for cider-library-present-p, before relying on anything in
the runtime
3. Make assumptions about the runtime explicit
My suggestion is =cider-connection-capabilities=.
Currently, there was an implicit assumption about the compilation
error format.

=cider-connection-capabilities=
Is my suggestion for 2.

=cider-repls=
Now returns cljs, if the repl capabilities include 'cljs
This way we can make a "plain" clj client, upgrade on connect with
cljs capability and have it be connected in cljs buffers.

This is more a concession / workaround the current repl-type setup.

In the future we might get rid of repl-type?
The only reason we have it, and creaating issue 3., is because we want
to be ergonomic about which buffer to use inside a given source
buffer.
I found that I am able to juggle multiple clients by swapping to the
buffer I want, thereby setting it active.

This can be a user command. Can also make a modeline element that
swaps between clj/cljs like calva.

slack discussion:
https://clojurians.slack.com/archives/C04CAKAGADU

CHANGELOG.md

@@ -17,6 +17,8 @@
 - [#3251](https://github.com/clojure-emacs/cider/pull/3251): Disable undo in `*cider-stacktrace*` buffers.
 - Consecutive overlays will not be spuriously deleted.
 - [#3260](https://github.com/clojure-emacs/cider/pull/3260): Scroll REPL buffer in other frame.
+- [#3061](https://github.com/clojure-emacs/cider/issues/3061): Allow
+  connect-clj for plain cljs repls (nbb etc).
 
 ## 1.5.0 (2022-08-24)
 

cider-connection.el

@@ -343,6 +343,14 @@ buffer."
        (when cider-auto-mode
          (cider-enable-on-existing-clojure-buffers))
 
+       (setf cider-connection-capabilities
+             (append
+              (pcase (cider-runtime)
+                ('clojure '(clojure jvm-compilation-errors))
+                ('babashka '(babashka jvm-compilation-errors))
+                (_ '()))
+              (when (cider-clojurescript-present-p) '(cljs))))
+
        (run-hooks 'cider-connected-hook)))))
 
 (defun cider--disconnected-handler ()
@@ -437,6 +445,22 @@ about this buffer (like variable `cider-repl-type')."
               (plist-get nrepl-endpoint :host)
               (plist-get nrepl-endpoint :port))))))
 
+(defun cider-clojurescript-present-p ()
+  "Return non nil when ClojureScript is present."
+  (nrepl-dict-get (cider-sync-tooling-eval "cljs.core/inc") "value"))
+
+(defvar-local cider-connection-capabilities '()
+  "A list of some of the capabilites of this connection buffer.
+Aka what assumptions we make about the runtime. Aka stuff we needed to make explicit
+in order for nbb to work.
+This is more genaral than `cider-nrepl-op-supported-p' and `cider-library-present-p'.
+But does not need to replace them.")
+
+(defun cider-connection-has-capability-p (capability)
+  "Return non nil when the cider connection has CAPABILITY."
+  (with-current-buffer (cider-current-repl)
+    (member capability cider-connection-capabilities)))
+
 
 ;;; Connection Management Commands
 
@@ -885,7 +909,13 @@ no linked session or there is no REPL of TYPE within the current session."
     (cond ((null buffer-repl-type) nil)
           ((or (null type) (eq type 'multi) (eq type 'any)) t)
           ((listp type) (member buffer-repl-type type))
-          (t (string= type buffer-repl-type)))))
+          (t
+           (or (string= type buffer-repl-type)
+               (let ((capabilities
+                      (buffer-local-value 'cider-connection-capabilities buffer)))
+                 (cond ((listp type)
+                        (cl-some (lambda (it) (member it capabilities)) type))
+                       (t (member type capabilities)))))))))
 
 (defun cider--get-host-from-session (session)
   "Returns the host associated with SESSION."

cider-eval.el

@@ -462,6 +462,13 @@ Uses the value of the `out' slot in RESPONSE."
    (cider-nrepl-sync-request:eval
     "(clojure.stacktrace/print-cause-trace *e)")))
 
+(defun cider-default-err-eval-print-handler ()
+  "Display the last exception without middleware support.
+When clojure.stracktrace is not present."
+  (cider--handle-err-eval-response
+   (cider-nrepl-sync-request:eval
+    "(println (ex-data *e))")))
+
 (defun cider--render-stacktrace-causes (causes &optional error-types)
   "If CAUSES is non-nil, render its contents into a new error buffer.
 Optional argument ERROR-TYPES contains a list which should determine the
@@ -498,9 +505,10 @@ into a new error buffer."
 (defun cider-default-err-handler ()
   "This function determines how the error buffer is shown.
 It delegates the actual error content to the eval or op handler."
-  (if (cider-nrepl-op-supported-p "stacktrace")
-      (cider-default-err-op-handler)
-    (cider-default-err-eval-handler)))
+  (cond ((cider-nrepl-op-supported-p "stacktrace") (cider-default-err-op-handler))
+        ((cider-library-present-p "clojure.stacktrace") (cider-default-err-eval-handler))
+        (t (cider-default-err-eval-print-handler))))
+
 
 ;; The format of the error messages emitted by Clojure's compiler changed in
 ;; Clojure 1.10.  That's why we're trying to match error messages to both the
@@ -739,7 +747,9 @@ when `cider-auto-inspect-after-eval' is non-nil."
                                    (cider-emit-interactive-eval-output out))
                                  (lambda (_buffer err)
                                    (cider-emit-interactive-eval-err-output err)
-                                   (unless cider-show-error-buffer
+                                   (when (or (not cider-show-error-buffer)
+                                             (not (cider-connection-has-capability-p 'jvm-compilation-errors)))
+
                                      ;; Display errors as temporary overlays
                                      (let ((cider-result-use-clojure-font-lock nil))
                                        (cider--display-interactive-eval-result

cider-overlays.el

@@ -303,6 +303,7 @@ focused."
   (let* ((font-value (if cider-result-use-clojure-font-lock
                          (cider-font-lock-as-clojure value)
                        value))
+         (font-value (string-trim-right font-value))
          (used-overlay (when (and point cider-use-overlays)
                          (cider--make-result-overlay font-value
                            :where point

cider-repl.el

@@ -153,7 +153,8 @@ you'd like to use the default Emacs behavior use
 (make-obsolete-variable 'cider-repl-print-level 'cider-print-options "0.21")
 
 (defvar cider-repl-require-repl-utils-code
-  '((clj . "(clojure.core/apply clojure.core/require clojure.main/repl-requires)")
+  '((clj . "(when-let [requires (resolve 'clojure.main/repl-requires)]
+  (clojure.core/apply clojure.core/require @requires))")
     (cljs . "(require '[cljs.repl :refer [apropos dir doc find-doc print-doc pst source]])")))
 
 (defcustom cider-repl-init-code (list (cdr (assoc 'clj cider-repl-require-repl-utils-code)))

cider.el

@@ -780,7 +780,7 @@ Generally you should not disable this unless you run into some faulty check."
 
 (defun cider-verify-clojurescript-is-present ()
   "Check whether ClojureScript is present."
-  (unless (cider-library-present-p "cljs.core")
+  (unless (cider-clojurescript-present-p)
     (user-error "ClojureScript is not available.  See https://docs.cider.mx/cider/basics/clojurescript for details")))
 
 (defun cider-verify-piggieback-is-present ()

test/cider-connection-tests.el

@@ -370,6 +370,26 @@
            (expect (cider-repls) :to-equal (list a b))
            (kill-buffer b)
            (expect (cider-repls) :to-equal (list a))
+           (sesman-unregister 'CIDER session))))))
+
+  (describe "cljs capability"
+    (it "Upgraded clj repl counts as cljs"
+      (let ((default-directory (expand-file-name "/tmp/some-dir")))
+        (cider-test-with-buffers
+         (a b)
+         (let ((session (list "some-session" a b)))
+           (with-current-buffer a
+             (setq cider-repl-type 'clj))
+           (with-current-buffer b
+             (setq cider-repl-type 'cljs))
+           (sesman-register 'CIDER session)
+           (expect (cider-repls 'cljs) :to-equal (list b))
+
+           (with-current-buffer a
+             (setf cider-connection-capabilities
+                   (append cider-connection-capabilities '(cljs))))
+
+           (expect (cider-repls) :to-equal (list a b))
            (sesman-unregister 'CIDER session)))))))
 
 (describe "cider--connection-info"