fix assoc on empty map. (closes #16).

Author: Yannick Scherer

src/rewrite_clj/zip/edit.clj

@@ -43,7 +43,8 @@
 (defn append-child
   "Append item as child of the current location. Will insert a space if necessary."
   [zloc item]
-  (let [r (-> zloc z/down z/rightmost)
+  (let [r' (z/down zloc)
+        r (when r' (z/rightmost r'))
         item (conv/->tree item)]
     (if (or (not r) (not (z/node r)) (zc/whitespace? r))
       (-> zloc (z/append-child item))

test/rewrite_clj/zip_test.clj

@@ -218,6 +218,11 @@
     (-> root (z/assoc 2 5) z/sexpr) => #{1 2 5}
     (-> root (z/assoc 5 8) z/sexpr) => (throws IndexOutOfBoundsException)
     (->> root (z/map #(z/edit % inc)) z/sexpr) => #{2 3 4})
+  (let [root (z/of-string "{}")]
+    root => z/seq?
+    root => z/map?
+    (z/sexpr root) => {}
+    (-> root (z/assoc :a 5) z/sexpr) => {:a 5})
   (let [root (z/of-string "{:a 1 :b 2}")]
     root => z/seq?
     root => z/map?