Merge pull request ReactiveX#1264 from akarnokd/ObserveOnScheduleUnsubscribe

ObserveOn scheduled unsubscription

Author: benjchristensen

rxjava-core/src/main/java/rx/operators/OperatorObserveOn.java

@@ -15,11 +15,13 @@
  */
 package rx.operators;
 
+import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 import java.util.concurrent.atomic.AtomicLongFieldUpdater;
 
 import rx.Observable.Operator;
 import rx.Scheduler;
 import rx.Subscriber;
+import rx.Subscription;
 import rx.functions.Action0;
 import rx.schedulers.ImmediateScheduler;
 import rx.schedulers.TrampolineScheduler;
@@ -59,6 +61,7 @@ public Subscriber<? super T> call(Subscriber<? super T> child) {
     private static final class ObserveOnSubscriber<T> extends Subscriber<T> {
         final Subscriber<? super T> observer;
         private final Scheduler.Worker recursiveScheduler;
+        private final ScheduledUnsubscribe scheduledUnsubscribe;
         final NotificationLite<T> on = NotificationLite.instance();
         /** Guarded by this. */
         private FastList queue = new FastList();
@@ -72,11 +75,15 @@ public ObserveOnSubscriber(Scheduler scheduler, Subscriber<? super T> subscriber
             super(subscriber);
             this.observer = subscriber;
             this.recursiveScheduler = scheduler.createWorker();
-            subscriber.add(recursiveScheduler);
+            this.scheduledUnsubscribe = new ScheduledUnsubscribe(recursiveScheduler);
+            subscriber.add(scheduledUnsubscribe);
         }
 
         @Override
         public void onNext(final T t) {
+            if (scheduledUnsubscribe.isUnsubscribed()) {
+                return;
+            }
             synchronized (this) {
                 queue.add(on.next(t));
             }
@@ -85,6 +92,9 @@ public void onNext(final T t) {
 
         @Override
         public void onCompleted() {
+            if (scheduledUnsubscribe.isUnsubscribed()) {
+                return;
+            }
             synchronized (this) {
                 queue.add(on.completed());
             }
@@ -93,6 +103,9 @@ public void onCompleted() {
 
         @Override
         public void onError(final Throwable e) {
+            if (scheduledUnsubscribe.isUnsubscribed()) {
+                return;
+            }
             synchronized (this) {
                 queue.add(on.error(e));
             }
@@ -153,4 +166,32 @@ public void add(Object o) {
             size = s + 1;
         }
     }
+    static final class ScheduledUnsubscribe implements Subscription {
+        final Scheduler.Worker worker;
+        volatile int once;
+        static final AtomicIntegerFieldUpdater<ScheduledUnsubscribe> ONCE_UPDATER
+                = AtomicIntegerFieldUpdater.newUpdater(ScheduledUnsubscribe.class, "once");
+
+        public ScheduledUnsubscribe(Scheduler.Worker worker) {
+            this.worker = worker;
+        }
+
+        @Override
+        public boolean isUnsubscribed() {
+            return once != 0;
+        }
+
+        @Override
+        public void unsubscribe() {
+            if (ONCE_UPDATER.getAndSet(this, 1) == 0) {
+                worker.schedule(new Action0() {
+                    @Override
+                    public void call() {
+                        worker.unsubscribe();
+                    }
+                });
+            }
+        }
+        
+    }
 }

rxjava-core/src/test/java/rx/operators/OperatorObserveOnTest.java

@@ -33,12 +33,14 @@
 
 import org.junit.Test;
 import org.mockito.InOrder;
+import static org.mockito.Matchers.anyInt;
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 
 import rx.Observable;
 import rx.Observer;
 import rx.Scheduler;
+import rx.exceptions.TestException;
 import rx.functions.Action0;
 import rx.functions.Action1;
 import rx.functions.Func1;
@@ -365,4 +367,26 @@ private static int randomIntFrom0to100() {
         x ^= (x << 4);
         return Math.abs((int) x % 100);
     }
+    
+    @Test
+    public void testDelayedErrorDeliveryWhenSafeSubscriberUnsubscribes() {
+        TestScheduler testScheduler = new TestScheduler();
+        
+        Observable<Integer> source = Observable.concat(Observable.<Integer>error(new TestException()), Observable.just(1));
+        
+        
+        @SuppressWarnings("unchecked")
+        Observer<Integer> o = mock(Observer.class);
+        InOrder inOrder = inOrder(o);
+        
+        source.observeOn(testScheduler).subscribe(o);
+        
+        inOrder.verify(o, never()).onError(any(TestException.class));
+        
+        testScheduler.advanceTimeBy(1, TimeUnit.SECONDS);
+        
+        inOrder.verify(o).onError(any(TestException.class));
+        inOrder.verify(o, never()).onNext(anyInt());
+        inOrder.verify(o, never()).onCompleted();
+    }
 }