Fix violations of the Observer contract.

Author: johngmyers

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

@@ -31,6 +31,7 @@
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
+import static rx.testing.TrustedObservableTester.assertTrustedObservable;
 
 /**
  * Returns a specified number of contiguous values from the start of an observable sequence.
@@ -97,12 +98,16 @@ public ItemObserver(Observer<T> observer) {
 
             @Override
             public void onCompleted() {
-                observer.onCompleted();
+                if (counter.getAndSet(num) < num) {
+                    observer.onCompleted();
+                }
             }
 
             @Override
             public void onError(Exception e) {
-                observer.onError(e);
+                if (counter.getAndSet(num) < num) {
+                    observer.onError(e);
+                }
             }
 
             @Override
@@ -129,7 +134,7 @@ public static class UnitTest {
         @Test
         public void testTake1() {
             Observable<String> w = Observable.toObservable("one", "two", "three");
-            Observable<String> take = Observable.create(take(w, 2));
+            Observable<String> take = Observable.create(assertTrustedObservable(take(w, 2)));
 
             @SuppressWarnings("unchecked")
             Observer<String> aObserver = mock(Observer.class);
@@ -144,7 +149,7 @@ public void testTake1() {
         @Test
         public void testTake2() {
             Observable<String> w = Observable.toObservable("one", "two", "three");
-            Observable<String> take = Observable.create(take(w, 1));
+            Observable<String> take = Observable.create(assertTrustedObservable(take(w, 1)));
 
             @SuppressWarnings("unchecked")
             Observer<String> aObserver = mock(Observer.class);
@@ -158,14 +163,23 @@ public void testTake2() {
 
         @Test
         public void testTakeDoesntLeakErrors() {
-            Observable<String> source = Observable.concat(Observable.from("one"), Observable.<String>error(new Exception("test failed")));
-            Observable.create(take(source, 1)).last();
+            Observable<String> source = Observable.create(new Func1<Observer<String>, Subscription>()
+            {
+                @Override
+                public Subscription call(Observer<String> observer)
+                {
+                    observer.onNext("one");
+                    observer.onError(new Exception("test failed"));
+                    return Subscriptions.empty();
+                }
+            });
+            Observable.create(assertTrustedObservable(take(source, 1))).last();
         }
 
         @Test
         public void testTakeZeroDoesntLeakError() {
-            Observable<String> source = Observable.<String>error(new Exception("test failed"));
-            Observable.create(take(source, 0)).lastOrDefault("ok");
+            Observable<String> source = Observable.error(new Exception("test failed"));
+            Observable.create(assertTrustedObservable(take(source, 0))).lastOrDefault("ok");
         }
 
         @Test
@@ -175,7 +189,7 @@ public void testUnsubscribeAfterTake() {
 
             @SuppressWarnings("unchecked")
             Observer<String> aObserver = mock(Observer.class);
-            Observable<String> take = Observable.create(take(w, 1));
+            Observable<String> take = Observable.create(assertTrustedObservable(take(w, 1)));
             take.subscribe(aObserver);
 
             // wait for the Observable to complete