cjohansen / cljsns

Reproducing a surprising ClojureScript build snag

ClojureScript externs woes

This repo reproduces a snag I just tripped on. I'm not sure if this is a bug or the exepected behavior.

This repo includes a single namespace, link.core. It also includes an external script that defines a function window.link.myfn. There is an externs file that informs the Closure compiler of the external script.

Development: works

If you run this in development, everything works as expected:

clojure -A:figwheel:build-dev
open resources/public/index.html

Now you can observe two printed messages in the console - one from ClojureScript and one from the external script being called from the ClojureScript namespace.

Production: no go

Now try to build this with advanced compilation settings:

clojure -A:figwheel:build-prod
open resources/public/prod.html

Open resources/public/index-prod.html and observe that the link object is now being overwritten by the app bundle - with an empty object. Result: prod build does not work.

Without the externs

Interestingly, if you drop the call to (js/link.myfn) and compile without the externs, no global link object is created at all:

clojure -A:figwheel:build-prod-noext
open resources/public/noext.html

Renaming the namespace

If you build the production build as before, but do not use overlapping names on the externed function and the namespace, things work as expected:

clojure -A:figwheel:build-other-ns
open resources/public/otherns.html