Meta The Meta (Use JVM repl for bb script development)

bb nrepl-server 0

Or just cider-jack-in. It will ask you for bb, if you have a bb.edn.

Babashkas nrepl is useful for interactively building scripts but the moment you like to use more complicated (cider) features, some stuff is not implemented.

Nrepl middleware support compatible with cider middleware would potentially unlock things like

• Cider inspector
• Cider debugger
• Keyword completions

I tried tricking Borkdude into solving the problems needed for cider middleware in bb. And I accidentally thought for 5 minutes it might be easy but yea, it is hard middlewares?.

It started brewing in me:

Just run a jvm nrepl for developing your script, it works.

Turns out the same was obvious to Martin Kavalar all along - [insert a link to babashka-conf talk].¹

The basic idea:

bb print-deps > deps.edn

(cider-jack-in-clj)

We are done, we have all the bb packages as dependencies, fs, process and friends. Now we develop our script as a usual Clojure jvm program with all our advanced Cider goodness.

• Development: jvm nrepl with bb deps loaded. All the dev goodness from our editors and middlewares.
• Production: bb process executing the code we have produced.

And since sci is a great Clojure implementation, everything just maps over.²

You are not trying to do anything serious like a production server with babashka anyway… right?³

Here be a script that might be useful:

#!/bin/bb

(ns bb_print_deps_or_alias
  (:require
   [clojure.java.shell :as shell]
   [clojure.pprint :as pp]
   [babashka.fs :as fs]))

(let [file (fs/file "deps.edn")
      deps (-> (shell/sh "bb" "print-deps") :out read-string)
      deps
      (if-not
          (fs/exists? file)
          deps
          (update-in
           (read-string (slurp file))
           [:aliases :bb :extra-deps]
           merge
           (:deps deps)))]
  (spit file (with-out-str (pp/pprint deps))))

In the basic case, it makes a deps.edn, else if there is a deps.edn already existing, it ads a bb alias.

Here is me using Emacs and Lispy to come up with the following:

(defun mm/cider-jack-in-babashka ()
  (interactive)
  (let ((cider-clojure-cli-aliases
         (concat
          cider-clojure-cli-aliases ":bb")))
    (cider-jack-in-clj nil)))

I give up on making the babashka nrepl even better. It is fine like this for my use cases. Instead, I will run a JVM repl for developing bb scripts.

This then means that more Clojure nrepl tooling efforts can flow into making the jvm nrepl good. And by doing so we get leverage into the bb development experience also.

Unfortunately, this does not help us when it comes to Nbb and Clojurescript. This is another front for tooling.

Since the door is open, would there be a way to have 1 jvm repl and develop Clojurescript?

• I did hack around with a babashka nrepl user land middleware #1529.
• Current overview issue: https://github.com/babashka/babashka.nrepl/issues/62