CLJS-3305: defrecord must implement IAssociative -contains-key?

Author: mfikes

src/main/clojure/cljs/core.cljc

@@ -1866,6 +1866,12 @@
                                this#
                                entry#)))
                         'IAssociative
+                        `(~'-contains-key? [this# ~ksym]
+                           ~(if (seq base-fields)
+                             `(case ~ksym
+                                (~@(map keyword base-fields)) true
+                                (cljs.core/contains? ~'__extmap ~ksym))
+                             `(cljs.core/contains? ~'__extmap ~ksym)))
                         `(~'-assoc [this# k# ~gs]
                            (condp keyword-identical? k#
                              ~@(mapcat (core/fn [fld]

src/test/cljs/cljs/core_test.cljs

@@ -1826,3 +1826,21 @@
 
 (deftest test-cljs-3271
   (is (== 0.6 (nth (range 0 1 0.1) 6))))
+
+(defrecord CLJS3305A [])
+(defrecord CLJS3305B [a b])
+
+(deftest test-cljs-3305
+  (let [empty-basis       (->CLJS3305A)
+        nonempty-basis    (->CLJS3305B 1 2)
+        empty-extended    (assoc empty-basis :y 1)
+        nonempty-extended (assoc nonempty-basis :y 1)]
+    (is (false? (contains? empty-basis       :a)))
+    (is (true?  (contains? nonempty-basis    :a)))
+    (is (false? (contains? nonempty-basis    :c)))
+    (is (true?  (contains? empty-extended    :y)))
+    (is (false? (contains? empty-extended    :z)))
+    (is (true?  (contains? nonempty-extended :a)))
+    (is (false? (contains? nonempty-extended :c)))
+    (is (true?  (contains? nonempty-extended :y)))
+    (is (false? (contains? nonempty-extended :z)))))