Support custom Jack-in command lines

[PEZ]

A way to make Calva Jack-in very flexible is to allow for a custom command line. Something like this setting in a connect sequence:

"customJackInCommandLine": "npx shadow-cljs -d <CIDER-NREPL-VERSION> watch :app some-arg-1 some-arg-2"

Would construct a fixed command line, which substitutes the cider-nrepl dependency version. So it would become:

npx shadow-cljs -d 0.28.5 watch :app some-arg-1 some-arg-2

This would allow the user to quite easily reach shadow-cljs features that the current jack-in convenience shuts you out from. The facility doesn't stop at letting us provide custom options to common Clojure tools, though, it would allow for any command line, including calling custom scripts.

Calva could make the following substitutions available to the command line construction:

From configuration:

• <NREPL-VERSION>
• <CIDER-NREPL-VERSION>
• <CIDER-PIGGIEBACK-VERSION>
• <NREPL-PORT-FILE>

Collected at Jack-in:

• <PROJECT-ROOT-PATH>
• <LEIN-PROFILES>
• <LEIN-LAUNCH-ALIAS>
• <CLJ-ALIASES>
• <CLJS-LAUNCH-BUILDS>

With this the above command line could be:

"customJackInCommandLine": "npx shadow-cljs -d <CIDER-NREPL-VERSION> watch <CLJS-LAUNCH-BUILDS> some-arg-1 some-arg-2"

Making it still allow the user to decide at Jack-in time which shadow-build to watch. The plural substitutions would be provided as a comma separated list. So :app,:test e.g.

Just like with any Jack-in, the command line will be executed with the jackInEnv provided in Calva configuration.

Here's an example Babashka script that doesn't start a REPL at all, just echoes the aliases and cider nrepl version:

#!/usr/bin/env bb

(require '[clojure.string :as str])

(defn parse-args [args]
  (loop [args args
         parsed {}]
    (if (empty? args)
      parsed
      (let [[flag value & rest-args] args]
        (case flag
          "--aliases" (recur rest-args (assoc parsed :aliases value))
          "--cider-nrepl-version" (recur rest-args (assoc parsed :cider-nrepl-version value))
          (do (println "Unknown parameter:" flag) (System/exit 1)))))))

(defn process-args [args]
  (let [aliases (str/split (:aliases args) #",")
        cider-nrepl-version (:cider-nrepl-version args)]
    (println "Aliases:")
    (doseq [alias aliases]
      (println alias))
    (println "CIDER nREPL version:" cider-nrepl-version)))

(def parsed-args (parse-args *command-line-args*))

(when (= *file* (System/getProperty "babashka.file"))
  (process-args parsed-args))

Please comment with your thoughts on this.