info-clj-cljs-variants

Table of Contents

• Intro
• JVM Clojure
• Regular ClojureScript
• Self-hosted ClojureScript

Intro

My little brain does not remember how to write conditional code for JVM cljs vs self-hosted cljs.

This repo is here as a refresher I can come back to and update as I learn more.

Clojure flavors I cover:

• JVM Clojure is what you’d expect, just regular old Clojure.

• Regular ClojureScript is compiled by the JVM and the one most folks are familiar with.

• Self-hosted ClojureScript (aka bootstrap ClojureScript) is ClojureScript compiled by ClojureScript.

As we all know, reader macros can be used to conditionally include code from .cljc source for JVM versions of Clojure and ClojureScript:

#?(:clj "Do this for Clojure"
   :cljs "Do this for ClojureScript")

What if we want to target regular vs self-hosted variants of ClojureScript, how do we do that?

To demonstrate one method, this repo has a macro demo-clj-variants\m1 that will return a different value based what flavor of Clojure it is run on.

Notice that cljs.cljc is brought in only for :cljs. Within that context, :clj means regular ClojureScript and :cljs means self-hosted ClojureScript.

I am no authority here, there are likely other ways to distinguish Clojure variants and conditionally include code for those variants, I just don’t know them yet.

Examples were run from bash on macOS.

To run the examples yourself, you’ll need Clojure and Planck.

JVM Clojure

$ clojure --eval "(require '[demo-clj-variants.entry :as entry]) (entry/testing123)"
"JVM clj"

Regular ClojureScript

$ clojure --main cljs.main \
          --eval "(require '[demo-clj-variants.entry :as entry]) (entry/testing123)"
"JVM cljs"

Self-hosted ClojureScript

$ planck --classpath src \
         --eval "(require '[demo-clj-variants.entry :as entry]) (entry/testing123)"
"self-hosted cljs"