LJS-1590: split, split-lines differs from Clojure on empty string

Only discard training if split generates more than one element

Author: spinningtopsofdoom

src/main/cljs/clojure/string.cljs

@@ -119,7 +119,7 @@
 
 (defn- discard-trailing-if-needed
   [limit v]
-  (if (== 0 limit)
+  (if (and (== 0 limit) (< 1 (count v)))
     (pop-last-while-empty v)
     v))
 

src/test/cljs/cljs/core_test.cljs

@@ -3132,6 +3132,12 @@
   (is  (=  (hash-set Infinity -Infinity 0 1 2 3 4 5 6 7 8)
           (set  (keys  (zipmap  [Infinity -Infinity 0 1 2 3 4 5 6 7 8]  (repeat nil)))))))
 
+(deftest test-cljs-1590
+  (is (= [""] (s/split "" #"\n")))
+  (is (= [] (s/split "\n\n\n" #"\n")))
+  (is (= [""] (s/split-lines "")))
+  (is (= [] (s/split-lines "\n\n\n"))))
+
 (comment
   ;; ObjMap
   ;; (let [ks (map (partial str "foo") (range 500))