CLJS-2911 Avoid infinite loop on infinite partitions

Author: slipset

src/main/cljs/cljs/core.cljs

@@ -9721,7 +9721,7 @@ reduces them without incurring seq initialization"
          (let [fst (first s)
                fv (f fst)
                run (cons fst (take-while #(= fv (f %)) (next s)))]
-           (cons run (partition-by f (seq (drop (count run) s)))))))))
+           (cons run (partition-by f (lazy-seq (drop (count run) s)))))))))
 
 (defn frequencies
   "Returns a map from distinct items in coll to the number of times

src/test/cljs/cljs/seqs_test.cljs

@@ -216,3 +216,7 @@
 (deftest test-cljs-2482
   (testing "seq on defrecord returns map entries"
     (is (every? map-entry? (seq (->Foo 1 2))))))
+
+(deftest test-cljs-2911
+  (testing "partition-by works correclty with infinite seqs"
+    (is (= (first (second (partition-by zero? (range)))) 1))))