[Fix #1789] Make it easier to change the connection of the scratch

buffer

It wasn't really apparent how one was supposed to change the connection
of a scratch buffer, so the relevant command was added to the mode's
menu.
I've also added another command to quickly toggle a buffer's connection
between Clojure and ClojureScript.

Author: bbatsov

CHANGELOG.md

@@ -12,6 +12,8 @@ request dispatch.
 within the scope of your current Emacs session.
 * [#1851](https://github.com/clojure-emacs/cider/issues/1851): Add a command to rerun the last test ran via `cider-test-run-test`. The new command is named `cider-test-rerun-test` and is about to `C-c C-t (C-)g`.
 * [#1748](https://github.com/clojure-emacs/cider/issues/1748): Add new interactive command `cider-pprint-eval-last-sexp-to-repl`.
+* [#1789](https://github.com/clojure-emacs/cider/issues/1789): Make it easy to change the connection of the cider-scratch buffer from the mode's menu.
+* New interactive command `cider-toggle-buffer-connection`.
 
 ### Changes
 

cider-client.el

@@ -205,6 +205,15 @@ such a link cannot be established automatically."
     (when conn
       (setq-local cider-connections (list conn)))))
 
+(defun cider-toggle-buffer-connection ()
+  "Toggles the current buffer's connection between Clojure and ClojureScript."
+  (interactive)
+  (cider-ensure-connected)
+  (let ((other-conn (cider-other-connection)))
+    (if other-conn
+        (setq-local cider-connections (list other-conn))
+      (user-error "No other connection available"))))
+
 (defun cider-clear-buffer-local-connection ()
   "Remove association between the current buffer and a connection."
   (interactive)

cider-scratch.el

@@ -32,12 +32,23 @@
 
 (require 'cider-interaction)
 (require 'clojure-mode)
+(require 'easymenu)
 
 (defvar cider-clojure-interaction-mode-map
   (let ((map (make-sparse-keymap)))
     (set-keymap-parent map clojure-mode-map)
     (define-key map (kbd "C-j") #'cider-eval-print-last-sexp)
     (define-key map [remap paredit-newline] #'cider-eval-print-last-sexp)
+    (easy-menu-define cider-clojure-interaction-mode-menu map
+      "Menu for Clojure Interaction mode"
+      '("Clojure Interaction"
+        (["Eval and print last sexp" #'cider-eval-print-last-sexp]
+         "--"
+         ["Reset" #'cider-scratch-reset]
+         "--"
+         ["Set buffer connection" #'cider-assoc-buffer-with-connection]
+         ["Toggle buffer connection" #'cider-toggle-buffer-connection]
+         ["Reset buffer connection" #'cider-clear-buffer-local-connection])))
     map))
 
 (defconst cider-scratch-buffer-name "*cider-scratch*")
@@ -62,14 +73,24 @@ before point, and prints its value into the buffer, advancing point.
 
 \\{cider-clojure-interaction-mode-map}")
 
+(defun cider--scratch-insert-welcome-message ()
+  "Insert the welcome message for the scratch buffer."
+  (insert ";; This buffer is for Clojure experiments and evaluation.\n"
+          ";; Press C-j to evaluate the last expression.\n\n"))
+
 (defun cider-create-scratch-buffer ()
   "Create a new scratch buffer."
   (with-current-buffer (get-buffer-create cider-scratch-buffer-name)
     (cider-clojure-interaction-mode)
-    (insert ";; This buffer is for Clojure experiments and evaluation.\n"
-            ";; Press C-j to evaluate the last expression.\n\n")
+    (cider--scratch-insert-welcome-message)
     (current-buffer)))
 
+(defun cider-scratch-reset ()
+  "Reset the current scratch buffer."
+  (interactive)
+  (erase-buffer)
+  (cider--scratch-insert-welcome-message))
+
 (provide 'cider-scratch)
 
 ;;; cider-scratch.el ends here