Possible duplication issue with ClojureScript :none compilation. Note the doubling of goog.require in the compiled core.js

alpha.cljs

(ns simple-test.alpha)

(def a-val 1)

beta.cljs

(ns simple-test.beta)

(def a-value :a-value)

core.cljs

(ns simple-test.core
  (:require [simple-test.alpha :as alpha]
            [simple-test.beta :refer [a-value]]
            [clojure.string :as test-external]))

(enable-console-print!)

(println "Hello world! " a-value)

core.js

// Compiled by ClojureScript 0.0-2411
goog.provide('simple_test.core');
goog.require('cljs.core');
goog.require('simple_test.beta');
goog.require('clojure.string');
goog.require('clojure.string');
goog.require('simple_test.beta');
goog.require('simple_test.alpha');
goog.require('simple_test.alpha');
cljs.core.enable_console_print_BANG_.call(null);
cljs.core.println.call(null,"Hello world! ",simple_test.beta.a_value);

//# sourceMappingURL=core.js.map?rel=1418555547209

project.clj

(defproject simple-test "0.1.0-SNAPSHOT"
  :description "FIXME: write this!"
  :url "http://example.com/FIXME"

  :dependencies [[org.clojure/clojure "1.6.0"]
                 [org.clojure/clojurescript "0.0-2411"]]

  :plugins [[lein-cljsbuild "1.0.4-SNAPSHOT"]]

  :source-paths ["src"]

  :cljsbuild {
    :builds [{:id "simple-test"
              :source-paths ["src"]
              :compiler {
                :output-to "simple_test.js"
                :output-dir "out"
                :optimizations :none
                :source-map true}}]})