I’ve been wanting to really get into using Clojure with the newer and preferred EDN tooling, over the older Leinengen tooling.

Initial Setup

First we’ll set up our directory and write a Hello World application.

brew install clojure 
mkdir learn-deps
cd learn-deps
touch deps.edn

then in deps.edn,

{
  :paths ["src/clj"]
  :deps {org.clojure/clojure {:mvn/version "1.12.1"}
}
mkdir -p src/clj/learn_deps
cd src/clj/learn_deps
touch core.clj
(ns learn-deps.core)

(defn -main []
  (println "Hello World!")
)

Then run from the root learn-deps/ directory as,

clj -M -m lean-deps.core

Using Aliases

We can simplify this command by adding an alias to deps.den,

{
  :paths ["src/clj"]
  :deps {org.clojure/clojure {:mvn/version "1.12.1"}
  :aliases {:run {:main-opts ["-m" "learn-deps.core"]}}
}

Then we can run this with the :run alias as,

clj -M:run

Using Calva from VS Code

As much as I love vim, I switched to VS Code for it’s Calva integration.

Start an interactive REPL with Calva in VS Code by adding this to deps.edn,

{
  :paths ["src/clj"]
  :deps {org.clojure/clojure {:mvn/version "1.12.1"}}
  :aliases {
    :run {:main-opts ["-m" "learn-deps.core"]}
    :repl {:extra-deps {nrepl/nrepl {:mvn/version "1.3.1"}}}       
  }
}

Then in VS Code, with Calva installed, type >jack into the command palette, and select, Calva: Start a PRoject REPL and Connect....

Calva should start up a REPL, then we can look for >load in the command palette, and select, Calva: Load/Evaluate Current File...

Then in the REPL window you can run (-main) and see the output of your main function.

References

This is adapted and update from an older YouTube video by Kelvin Mai.