Prettier for Ruby in spacemacs

Currently, spacemacs' Ruby layer does not support choosing a formatter, like e.g. the TypeScript layer. I love being able to type code without thinking about formatting, hit :w, and watch my file beautify itself.

I've started using @prettier/plugin-ruby at work, and wanted the experience I get with my TypeScript code, with my Ruby code. To that end, I wrote my very first elisp!

(defun ruby-prettier ()
  (interactive)
  (when (eq major-mode 'ruby-mode))
    (shell-command-to-string (format "yarn prettier --write %s" buffer-file-name))
    (revert-buffer :ignore-auto :noconfirm)))

(add-hook 'after-save-hook 'ruby-prettier)

For the time being, I've dumped this function into dotspacemacs/user-config and it works! There is a noticeable half-second pause while this formats my code, something I haven't noticed when using prettier with TypeScript files. I don't know why.