CLJS-1449: self-host: Error if :require-macros with :as

The k argument to cljs.js/load-macros should be either
a keyword or nil. The current implementation employs
an or construct that can set k to be the value false, and
when ultimately passed back into load-macros this
false value can inadvertently be used as a function.

This patch

a) revises the or construct to terminate wil a nil,
   ensuring k will be be set to nil where previously it
   would have been set to false

b) revises a spot where k is used to look up a value
   in a map, reversing things so that the map is
   instead used as the (non-nil) fn

Author: mfikes

src/main/cljs/cljs/js.cljs

@@ -353,9 +353,10 @@
 (defn- load-macros [bound-vars k macros reload reloads opts cb]
   (if (seq macros)
     (let [nsym (first (vals macros))
-          k    (or (k reload)
+          k    (or (reload k)
                    (get-in reloads [k nsym])
-                   (and (= nsym name) (:*reload-macros* bound-vars) :reload))]
+                   (and (= nsym name) (:*reload-macros* bound-vars) :reload)
+                   nil)]
       (require bound-vars nsym k
         (-> opts
           (assoc :macros-ns true)

src/test/self/self_host/test.cljs

@@ -154,6 +154,26 @@
           (is (= "1\n2\n" value))
           (inc! l))))))
 
+(deftest test-eval-str-with-require-macros
+  (async done
+    (let [l (latch 2 done)]
+      (cljs/eval-str st
+        "(ns cljs.user (:require-macros [cljs.user.macros]))"
+        nil
+        {:eval node-eval
+         :load (fn [_ cb] (cb {:lang :clj :source "(ns cljs.user.macros)"}))}
+        (fn [{:keys [value error]}]
+          (is (nil? error))
+          (inc! l)))
+      (cljs/eval-str st
+        "(ns cljs.user (:require-macros [cljs.user.macros :as cljs-user-macros]))"
+        nil
+        {:eval node-eval
+         :load (fn [_ cb] (cb {:lang :clj :source "(ns cljs.user.macros)"}))}
+        (fn [{:keys [error value]}]
+          (is (nil? error))
+          (inc! l))))))
+
 #_(deftest test-eval-str-with-require
   (async done
     (let [l (latch 3 done)]