CIDER has way too many special buffers, doesn’t it? Immediately a few come to my mind - the REPL buffer, the stacktrace buffer, the profiler buffer, the scratch buffer, the docs buffer and the nREPL messages buffer. There are easy ways to summon some of them (e.g. the REPL buffer with C-c C-z), but not all. Usually you’d be looking the CIDER buffers up using C-x b (switch-buffer) and whatever completion front-end you’re using.1 Is there a better way to handle navigation to and from those special buffers?

Turns out there is! Enter the little known cider-selector command, bound by default to C-c M-s. The usage of the command is extremely simple - after invoking it you need to type a single key identifying the target buffer (e.g. r for the REPL) and that’s it.

Here’s a list of all of cider-selectors’s keybindings:

Keyboard Shortcut Description
c Most recently visited Clojure buffer.
e Most recently visited Emacs Lisp buffer.
r Current REPL buffer or most recently visited REPL buffer.
m *nrepl-messages* buffer.
x *cider-error* buffer.
d *cider-doc* buffer.
p *cider-profiler* buffer.
s *cider-scratch* buffer.
q Abort.
? Show help.

Any of those keys can be prefixed with a 4 to make the target buffer open in a different window (as opposed to the current one).

One thing to keep in mind about the default keybinding C-c M-s is that it’s available only in buffers where cider-mode is enabled (e.g. Clojure source buffers) and in the CIDER REPL. If you want to have it available everywhere it might be a good idea to add a global binding in your Emacs config:

(global-set-key (kbd "C-c s") #'cider-selector)

One cool thing that you probably noticed is that there are also shortcuts for going back to whatever is the most recently used Clojure or Emacs Lisp buffer.2 Another cool thing is that you can easily extend the selector with new commands using def-cider-selector-method:

(def-cider-selector-method ?z
  "CIDER foo buffer."

I’d be really curious to hear your ideas about additional selector actions!

The cider-selector command will be familiar to users of SLIME (CIDER’s main inspiration), as we borrowed it from there. Perhaps we could have named it better, but you know… naming is hard! Rest assured, despite its weird name it’s pretty useful!

That’s all I have for you today. This episode was brought to you by Clojurists Together. They are awesome and so are all of you! Keep hacking!

  1. I’m quite fond of ivy

  2. I hope this will motivate some of you to work on CIDER itself.