Implement CompletionStage whenComplete

Author: cosineblast

src/manifold/deferred.clj

@@ -71,7 +71,9 @@
          then-handle then-handle-async
          then-exceptionally
 
-         to-completable-future)
+         to-completable-future
+
+         when-complete when-complete-async)
 
 ;; The potemkin abstract type for
 ;; implementations such as CompletionStage
@@ -158,7 +160,14 @@
     (then-exceptionally this operator))
 
   (toCompletableFuture [this]
-    (to-completable-future this)))
+    (to-completable-future this))
+
+  (whenComplete [this operator]
+    (when-complete this operator))
+  (whenCompleteAsync [this operator]
+    (when-complete-async this operator))
+  (whenCompleteAsync [this operator executor]
+    (when-complete-async this operator executor)))
 
 (definline realized?
   "Returns true if the manifold deferred is realized."
@@ -1638,8 +1647,16 @@
                  #(.complete result %)
                  #(.completeExceptionally result %))
 
-    result
-    ))
+    result))
+
+(defn- when-complete [this ^java.util.function.BiConsumer operator]
+  (assert-some operator)
+  (on-realized this
+               #(.accept operator % nil)
+               #(.accept operator nil %))
+  this)
+
+(def ^:private when-complete-async (async-for when-complete))
 
 ;;;
 

test/manifold/deferred_stage_test.clj

@@ -479,3 +479,60 @@
       (is (.isDone target))
 
       (is (thrown? RuntimeException (.getNow target nil))))))
+
+
+
+(def when-complete-methods
+  [(fn [^CompletionStage this operator _]
+     (.whenComplete this operator))
+   (fn [^CompletionStage this operator _]
+     (.whenCompleteAsync this operator))
+   (fn [^CompletionStage this operator executor]
+     (.whenCompleteAsync this operator executor))])
+
+(defn- test-when-complete-success [method executor]
+
+  (let [was-called (atom false)
+
+        d1 (d/success-deferred 1)
+        d2 (method
+            d1
+            (fn->BiConsumer
+             (fn [x t]
+               (is (= 1 x))
+               (is (nil? t))
+               (reset! was-called true)))
+            executor)]
+
+    (is (= @d1 1))
+    (is (= @d2 1))
+    (is (= true @was-called))))
+
+(defn- test-when-complete-error [method executor]
+
+  (let [was-called (atom false)
+
+        d1 (d/error-deferred (RuntimeException.))
+        d2 (method
+            d1
+            (fn->BiConsumer
+             (fn [x t]
+               (is (nil? x))
+               (is (some? t))
+               (reset! was-called true)))
+            executor)]
+
+    (is (thrown? RuntimeException @d1))
+    (is (thrown? RuntimeException @d2))
+    (is (= true @was-called))))
+
+(deftest test-when-complete
+
+  (let [executor (Executors/newSingleThreadExecutor)]
+    (testing "when complete success"
+      (dorun (for [method when-complete-methods]
+               (test-when-complete-success method executor))))
+
+    (testing "when complete error"
+      (dorun (for [method when-complete-methods]
+               (test-when-complete-error method executor))))))