feat(common-lisp): set custom repl opener

After some experimentation, calling `sly` non-interactively when no
Slynk connection involves some strange async affects which displease the
REPL-opening code. Instead, we start the Slynk process, wait while it
loads, and then finally connect with the usual `sly-mrepl`, whose Elisp
would have been loaded by this point.

modules/lang/common-lisp/autoload/common-lisp.el

@@ -3,3 +3,17 @@
 ;; HACK Fix #1772: void-variable sly-contribs errors due to sly packages (like
 ;; `sly-macrostep') trying to add to `sly-contribs' before it is defined.
 ;;;###autoload (defvar sly-contribs '(sly-fancy))
+
+;;;###autoload
+(defun +lisp/open-repl ()
+  "Open the Sly REPL."
+  (interactive)
+  (require 'sly)
+  (if (sly-connected-p) (sly-mrepl)
+    (sly nil nil t)
+    (cl-labels ((recurse (attempt)
+                  (sleep-for 1)
+                  (cond ((sly-connected-p) (sly-mrepl))
+                        ((> attempt 5) (error "Failed to start Slynk process."))
+                        (t (recurse (1+ attempt))))))
+      (recurse 1))))

modules/lang/common-lisp/config.el

@@ -24,7 +24,7 @@
     (remove-hook 'lisp-mode-hook #'sly-editing-mode))
 
   (after! lisp-mode
-    (set-repl-handler! 'lisp-mode #'sly-mrepl)
+    (set-repl-handler! 'lisp-mode #'+lisp/open-repl)
     (set-eval-handler! 'lisp-mode #'sly-eval-region)
     (set-lookup-handlers! 'lisp-mode
       :definition #'sly-edit-definition