@viebel: that seems more like a cljsbuild question?

What is passed here: https://github.com/technomancy/leiningen/blob/master/sample.project.clj#L322 ?

p is the project map

$ pwd
/Users/me/Developer/clojure/sente
$ lein pprint :root
"/Users/me/Developer/clojure/sente"

I didn’t realise this was a feature, but it looks like Leiningen will pass the project map to any functions which are keys