CLJS-1422: cljs.js/eval-str fails for ns form on node.js with simple optimizations

The special case of find-ns-obj for node.js under optimizations now
guards the eval of the initial path segment, catching ReferenceError.
This fixes eval-str of ns forms.

Author: michaelballantyne

src/main/cljs/cljs/core.cljs

@@ -10135,7 +10135,16 @@ Maps become Objects. Arbitrary keys are encoded to by key->js."
         segs (.split munged-ns ".")]
     (case *target*
       "nodejs"  (if ^boolean js/COMPILED
-                  (js/eval munged-ns)
+                  ; Under simple optimizations on nodejs, namespaces will be in module
+                  ; rather than global scope and must be accessed by a direct call to eval.
+                  ; The first segment may refer to an undefined variable, so its evaluation
+                  ; may throw ReferenceError.
+                  (find-ns-obj*
+                    (try
+                      (js/eval (first segs))
+                      (catch js/ReferenceError e
+                        nil))
+                    (next segs))
                   (find-ns-obj* js/global segs))
       "default" (find-ns-obj* goog/global segs)
       (throw (js/Error. (str "find-ns-obj not supported for target " *target*))))))

src/test/self/self_host/test.cljs

@@ -124,7 +124,7 @@
           (is (nil? error))
           (is (== 3 value))
           (inc! l)))
-      #_(cljs/eval-str st "(ns foo.bar)" nil
+      (cljs/eval-str st "(ns foo.bar)" nil
           {:eval node-eval
            :context :expr
            :def-emits-var true}