Port CLJS-2568: clojure.walk now retains metadata when walking lists and seqs

Co-authored-by: Alex Miller <alex.miller@cognitect.com>

Author: swannodette

src/main/cljs/clojure/walk.cljs

@@ -43,10 +43,10 @@ the sorting function."}
   {:added "1.1"}
   [inner outer form]
   (cond
-    (list? form)      (outer (apply list (map inner form)))
+    (list? form)      (outer (with-meta (apply list (map inner form)) (meta form)))
     (map-entry? form)
     (outer (MapEntry. (inner (key form)) (inner (val form)) nil))
-    (seq? form)       (outer (doall (map inner form)))
+    (seq? form)       (outer (with-meta (doall (map inner form)) (meta form)))
     (record? form)    (outer (reduce (fn [r x] (conj r (inner x))) form form))
     (coll? form)      (outer (into (empty form) (map inner form)))
     :else             (outer form)))

src/test/cljs/cljs/walk_test.cljs

@@ -80,3 +80,14 @@
   (let [coll [:html {:a ["b" 1]} ""]
         f (fn [e] (if (and (vector? e) (not (map-entry? e))) (apply list e) e))]
     (is (= (list :html {:a (list "b" 1)} "") (w/postwalk f coll)))))
+
+(defrecord RM [a])
+(deftest retain-meta
+  (let [m {:foo true}]
+    (are [o] (= m (meta (w/postwalk identity (with-meta o m))))
+      '(1 2)
+      [1 2]
+      #{1 2}
+      {1 2}
+      (map inc (range 3))
+      (->RM 1))))