How to use “foreign” JavaScript dependencies in Clojurescript?

Question

I'm trying to wrap my head around using "foreign" JavaScript dependencies in Clojurescript . I've read most everything Google has to offer on this topic but I still fail to understand this process. In particular, I'm interested how to depend on the jsonld.js library from Clojurescript.

Some points I don't get:

1. Do you put :foreign-libs into deps.cljs or compiler options (eg, :compiler map in project.clj)?

2. Is the value of :file in :foreign-libs interpreted as a Java resource? Where do you put the JavaScript files you use as foreign libraries? I tried putting them into resources and elsewhere, but all my attempts resulted in java.lang.NullPointerException .

Steps to reproduce:

# Create an empty Clojurescript project
lein new figwheel jsonld

# Download jsonld.js library
cd jsonld/resources
curl -O http://cdnjs.cloudflare.com/ajax/libs/jsonld/0.3.15/jsonld.js

# Configure foreign libs in project.clj.
# Add the following into `:compiler` in the dev build:
# :foreign-libs {:file "resources/jsonld.js"
#                :provides ["jsonld"]}

lein figwheel # => java.lang.NullPointerException

Alternatively, if I provide deps.cljs with the following content:

{:foreign-libs {:file "jsonld.js"
                :provides ["jsonld"]}}

Then Figwheel starts, but when I call (require '[jsonld]) , I get this error:

WARNING: JavaScript file found on classpath for library `jsonld`, but does not contain a corresponding `goog.provide` declaration
clojure.lang.ExceptionInfo: No such namespace: jsonld, could not locate jsonld.cljs, jsonld.cljc, or Closure namespace "jsonld" {:tag :cljs/analysis-error}

Answer 1

Update: The :foreign-libs option takes a vector of foreign libs and not a single map.

The :foreign-libs option can either be supplied to the compiler directly or via a deps.cljs file within jars. deps.cljs is mostly useful when you want to package a Javascript library within a jar that other people may use — maybe useful later but not what you need right now.

You can find more information about the compiler option in the wiki . There also is a page specifically about using/packaging foreign dependencies in ClojureScript .

I think in your particular example the problem is the path you're supplying as :file . The path is classpath-relative and the contents of the resources/ directory are added to the classpath, meaning if you want to point to resources/jsonld.js in a classpath-relative way it's just jsonld.js .

PS: You can also supply URLs as :file and the compiler will download them for you.