CLJS-3356: halt-when not usable within #'c.c/into

Author: mfikes

src/main/cljs/cljs/core.cljs

@@ -5262,7 +5262,11 @@ reduces them without incurring seq initialization"
        (reduce conj to from)))
   ([to xform from]
      (if (implements? IEditableCollection to)
-       (-with-meta (persistent! (transduce xform conj! (transient to) from)) (meta to))
+       (let [tm (meta to)
+             rf (fn
+                  ([coll] (-> (persistent! coll) (-with-meta tm)))
+                  ([coll v] (conj! coll v)))]
+         (transduce xform rf (transient to) from))
        (transduce xform conj to from))))
 
 (defn mapv

src/test/cljs/cljs/core_test.cljs

@@ -387,6 +387,15 @@
   (testing "CLJS-2258"
     (is (= ["1"] (sequence (map str) (eduction [1]))))))
 
+(deftest test-into+halt-when
+  (is (= :anomaly (into [] (comp (filter some?) (halt-when #{:anomaly}))
+                    [1 2 3 :anomaly 4])))
+  (is (= {:anomaly         :oh-no!,
+          :partial-results [1 2]}
+        (into []
+          (halt-when :anomaly #(assoc %2 :partial-results %1))
+          [1 2 {:anomaly :oh-no!} 3 4]))))
+
 (deftest test-obj-equiv
   (testing "Object equiv method"
     (is (.equiv :foo :foo))
@@ -1282,7 +1291,7 @@
            [5 4]))
     (is (= (transduce (halt-when #{1} (fn [ret input] (conj ret input))) conj [] [5 4 1 2 3])
            [5 4 1]))
-    (is (= (into [] (halt-when #{1} (fn [ret in] (conj! ret in))) [2 3 1])
+    (is (= (into [] (halt-when #{1} (fn [ret in] (conj ret in))) [2 3 1])
           [2 3 1]))))
 
 (deftest test-cljs-1839