CLJS-1199 array-map should skip dropped elements of IndexedSeq

Author: tonsky

src/cljs/cljs/core.cljs

@@ -7448,7 +7448,7 @@ reduces them without incurring seq initialization"
   "keyval => key val
   Returns a new array map with supplied mappings."
   [& keyvals]
-  (let [arr (if (instance? IndexedSeq keyvals)
+  (let [arr (if (and (instance? IndexedSeq keyvals) (zero? (.-i keyvals)))
               (.-arr keyvals)
               (into-array keyvals))]
     (.fromArray cljs.core/PersistentArrayMap arr true false)))

test/cljs/cljs/core_test.cljs

@@ -2686,7 +2686,7 @@
 (defn foo-set [x]
   (first x))
 
-(deftest test-cljs-982-var-deref []
+(deftest test-cljs-982-var-deref
   (let [f (foo-var #'foo-set)]
     (is (= (f [1 2 3]) 1))
     (set! foo-set (fn [x] :oops))
@@ -2731,17 +2731,21 @@
       :foo #'foo-1187
       :bar #'bar-1187) []))
 
-(deftest test-cljs-1187 []
+(deftest test-cljs-1187
   (testing "Internal var nodes analyzed in expression context"
     (is (= (with-out-str (print-foo-1187 :foo))
            "foo!"))))
 
-(deftest test-cljs-1189 []
+(deftest test-cljs-1189
   (testing "array-map should always return array maps"
     (let [am (apply array-map (range 100))]
       (is (== (count am) 50))
       (is (instance? PersistentArrayMap am)))))
 
+(deftest test-cljs-1199
+  (testing "array-map should skip dropped elements of IndexedSeq"
+    (is (= {:a 1} (apply array-map (drop 1 [0 :a 1]))))))
+
 (comment
   ;; ObjMap
   ;; (let [ks (map (partial str "foo") (range 500))