CLJS-3333: defonce expansion non-hygienic with respect to core names

Author: mfikes

src/main/clojure/cljs/core.cljc

@@ -618,8 +618,11 @@
   "defs name to have the root value of init iff the named var has no root value,
   else init is unevaluated"
   [x init]
-  `(when-not (exists? ~x)
-     (def ~x ~init)))
+  (core/let [qualified (if (namespace x)
+                         x
+                         (symbol (core/str (core/-> &env :ns :name)) (name x)))]
+    `(when-not (exists? ~qualified)
+       (def ~x ~init))))
 
 (core/defn destructure [bindings]
   (core/let [bents (partition 2 bindings)

src/test/cljs/cljs/core_test.cljs

@@ -1874,3 +1874,7 @@
             (for [e s :when (and (sequential? e) (every? (fn [x] x) e))]
               e))
           [[]]))))
+
+(deftest test-cljs-3333
+  (defonce not-native 17)   ;; Intentionally matching a core name
+  (is (== 17 not-native)))