Using Calva with nbb

Since nbb can be started such that it is an nREPL server, Calva can connect to it and a lot of the features will work.

Calva can also start nbb and connect its REPL for you, using the Jack-in command. This will start an nbb nREPL server on a random port and connect Calva to it. Check out this video where they use Calva and nbb to create a CLI tool as an executable npm module:

In that video they ask for a JavaScript to ClojureScript converter. And there is one: https://mauricioszabo.gitlab.io/js2cljs/

Though if you are using Calva, this converter is easier to use directly via the command Calva: Convert JavaScript to ClojureScript:

Errors jacking in to nbb on Windows?

On some machines it seems necessary to first run npx nbb from the CMD prompt to make jack-in work. Or try first install it npm i -g nbb. (You probabl want nbb installed globally anyway.)

Don't expect complete support

nbb's nREPL server is completely new and and WIP. It will be a bit limited compared to a full cider-nrepl enhanced "regular" Clojure nREPL server. Things like function signatures, and more do not work.

It's a bit hacky

The nbb nREPL server is the first ClojureScript nREPL server around and throws Calva's assumption that an nREPL server is always started in a Clojure process out the window. The nbb Jack-in/connect option ”pretends” it is connecting to a Clojure nREPL and then the code fro promoting the nREPL session to a ClojureScript one is just dummy code.

This means that if you open a Clojure (.clj) file while connected to an nbb nREPL server, it will still be a ClojureScript session serving even though Calva will indicate that it is a Clojure one. Bare with us until we can fix this properly in Calva.