CLJ-2027 Defer calling empty until later in namespace map printing

Signed-off-by: Stuart Halloway <stu@cognitect.com>

Author: puredanger

src/clj/clojure/core_print.clj

@@ -236,15 +236,15 @@
   (when *print-namespace-maps*
     (loop [ns nil
            [[k v :as entry] & entries] (seq m)
-           lm (empty m)]
+           lm {}]
       (if entry
         (when (or (keyword? k) (symbol? k))
           (if ns
             (when (= ns (namespace k))
               (recur ns entries (assoc lm (strip-ns k) v)))
             (when-let [new-ns (namespace k)]
               (recur new-ns entries (assoc lm (strip-ns k) v)))))
-        [ns lm]))))
+        [ns (apply conj (empty m) lm)]))))
 
 (defmethod print-method clojure.lang.IPersistentMap [m, ^Writer w]
   (print-meta m w)

test/clojure/test_clojure/printer.clj

@@ -136,4 +136,7 @@
 
 (deftest print-ns-maps
   (is (= "#:user{:a 1}" (binding [*print-namespace-maps* true] (pr-str {:user/a 1}))))
-  (is (= "{:user/a 1}" (binding [*print-namespace-maps* false] (pr-str {:user/a 1})))))
+  (is (= "{:user/a 1}" (binding [*print-namespace-maps* false] (pr-str {:user/a 1}))))
+  (let [date-map (bean (java.util.Date. 0))]
+    (is (= (binding [*print-namespace-maps* true] (pr-str date-map))
+           (binding [*print-namespace-maps* false] (pr-str date-map))))))