OperatorReduce - prevent multiple terminal events

src/main/java/rx/internal/operators/OnSubscribeReduce.java

@@ -22,6 +22,7 @@
 import rx.Observable.OnSubscribe;
 import rx.exceptions.Exceptions;
 import rx.functions.Func2;
+import rx.plugins.RxJavaHooks;
 
 public final class OnSubscribeReduce<T> implements OnSubscribe<T> {
 
@@ -57,6 +58,8 @@ static final class ReduceSubscriber<T> extends Subscriber<T> {
 
         static final Object EMPTY = new Object();
 
+        boolean done;
+
         @SuppressWarnings("unchecked")
         public ReduceSubscriber(Subscriber<? super T> actual, Func2<T, T, T> reducer) {
             this.actual = actual;
@@ -68,6 +71,9 @@ public ReduceSubscriber(Subscriber<? super T> actual, Func2<T, T, T> reducer) {
         @SuppressWarnings("unchecked")
         @Override
         public void onNext(T t) {
+            if (done) {
+                return;
+            }
             Object o = value;
             if (o == EMPTY) {
                 value = t;
@@ -77,19 +83,28 @@ public void onNext(T t) {
                 } catch (Throwable ex) {
                     Exceptions.throwIfFatal(ex);
                     unsubscribe();
-                    actual.onError(ex);
+                    onError(ex);
                 }
             }
         }
 
         @Override
         public void onError(Throwable e) {
-            actual.onError(e);
+            if (!done) {
+                done = true;
+                actual.onError(e);
+            } else {
+                RxJavaHooks.onError(e);
+            }
         }
 
         @SuppressWarnings("unchecked")
         @Override
         public void onCompleted() {
+            if (done) {
+                return;
+            }
+            done = true;
             Object o = value;
             if (o != EMPTY) {
                 actual.onNext((T)o);

src/test/java/rx/internal/operators/OnSubscribeReduceTest.java

@@ -0,0 +1,277 @@
+/**
+ * Copyright 2014 Netflix, Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package rx.internal.operators;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Matchers.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import rx.*;
+import rx.Observable.OnSubscribe;
+import rx.Observer;
+import rx.exceptions.TestException;
+import rx.functions.Action1;
+import rx.functions.Func1;
+import rx.functions.Func2;
+import rx.internal.util.UtilityFunctions;
+import rx.observers.TestSubscriber;
+import rx.plugins.RxJavaHooks;
+
+public class OnSubscribeReduceTest {
+    @Mock
+    Observer<Object> observer;
+
+    @Before
+    public void before() {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    Func2<Integer, Integer, Integer> sum = new Func2<Integer, Integer, Integer>() {
+        @Override
+        public Integer call(Integer t1, Integer t2) {
+            return t1 + t2;
+        }
+    };
+
+    @Test
+    public void testAggregateAsIntSum() {
+
+        Observable<Integer> result = Observable.just(1, 2, 3, 4, 5).reduce(0, sum).map(UtilityFunctions.<Integer> identity());
+
+        result.subscribe(observer);
+
+        verify(observer).onNext(1 + 2 + 3 + 4 + 5);
+        verify(observer).onCompleted();
+        verify(observer, never()).onError(any(Throwable.class));
+    }
+
+    @Test
+    public void testAggregateAsIntSumSourceThrows() {
+        Observable<Integer> result = Observable.concat(Observable.just(1, 2, 3, 4, 5),
+                Observable.<Integer> error(new TestException()))
+                .reduce(0, sum).map(UtilityFunctions.<Integer> identity());
+
+        result.subscribe(observer);
+
+        verify(observer, never()).onNext(any());
+        verify(observer, never()).onCompleted();
+        verify(observer, times(1)).onError(any(TestException.class));
+    }
+
+    @Test
+    public void testAggregateAsIntSumAccumulatorThrows() {
+        Func2<Integer, Integer, Integer> sumErr = new Func2<Integer, Integer, Integer>() {
+            @Override
+            public Integer call(Integer t1, Integer t2) {
+                throw new TestException();
+            }
+        };
+
+        Observable<Integer> result = Observable.just(1, 2, 3, 4, 5)
+                .reduce(0, sumErr).map(UtilityFunctions.<Integer> identity());
+
+        result.subscribe(observer);
+
+        verify(observer, never()).onNext(any());
+        verify(observer, never()).onCompleted();
+        verify(observer, times(1)).onError(any(TestException.class));
+    }
+
+    @Test
+    public void testAggregateAsIntSumResultSelectorThrows() {
+
+        Func1<Integer, Integer> error = new Func1<Integer, Integer>() {
+
+            @Override
+            public Integer call(Integer t1) {
+                throw new TestException();
+            }
+        };
+
+        Observable<Integer> result = Observable.just(1, 2, 3, 4, 5)
+                .reduce(0, sum).map(error);
+
+        result.subscribe(observer);
+
+        verify(observer, never()).onNext(any());
+        verify(observer, never()).onCompleted();
+        verify(observer, times(1)).onError(any(TestException.class));
+    }
+
+    @Test
+    public void testBackpressureWithNoInitialValue() throws InterruptedException {
+        Observable<Integer> source = Observable.just(1, 2, 3, 4, 5, 6);
+        Observable<Integer> reduced = source.reduce(sum);
+
+        Integer r = reduced.toBlocking().first();
+        assertEquals(21, r.intValue());
+    }
+
+    @Test
+    public void testBackpressureWithInitialValue() throws InterruptedException {
+        Observable<Integer> source = Observable.just(1, 2, 3, 4, 5, 6);
+        Observable<Integer> reduced = source.reduce(0, sum);
+
+        Integer r = reduced.toBlocking().first();
+        assertEquals(21, r.intValue());
+    }
+
+    @Test
+    public void testNoInitialValueDoesNotEmitMultipleTerminalEvents() {
+        TestSubscriber<Integer> ts = TestSubscriber.create();
+        Observable.create(new OnSubscribe<Integer>() {
+
+            @Override
+            public void call(final Subscriber<? super Integer> sub) {
+                sub.setProducer(new Producer() {
+
+                    @Override
+                    public void request(long n) {
+                        if (n > 0) {
+                            sub.onNext(1);
+                            sub.onNext(2);
+                            sub.onCompleted();
+                        }
+                    }
+                });
+            }
+        })
+        .reduce(new Func2<Integer, Integer, Integer>() {
+
+            @Override
+            public Integer call(Integer a, Integer b) {
+                throw new RuntimeException("boo");
+            }})
+        .unsafeSubscribe(ts);
+        ts.assertError(RuntimeException.class);
+        ts.assertNotCompleted();
+    }
+
+    @Test
+    public void testNoInitialValueUpstreamEmitsMoreOnNextDespiteUnsubscription() {
+        TestSubscriber<Integer> ts = TestSubscriber.create();
+        Observable.create(new OnSubscribe<Integer>() {
+
+            @Override
+            public void call(final Subscriber<? super Integer> sub) {
+                sub.setProducer(new Producer() {
+
+                    @Override
+                    public void request(long n) {
+                        if (n > 2) {
+                            sub.onNext(1);
+                            sub.onNext(2);
+                            sub.onNext(3);
+                            sub.onCompleted();
+                        }
+                    }
+                });
+            }
+        })
+        .reduce(new Func2<Integer, Integer, Integer>() {
+            boolean once = true;
+
+            @Override
+            public Integer call(Integer a, Integer b) {
+                if (once) {
+                    throw new RuntimeException("boo");
+                } else {
+                    once = false;
+                    return a + b;
+                }
+            }})
+        .unsafeSubscribe(ts);
+        ts.assertNoValues();
+        ts.assertError(RuntimeException.class);
+        ts.assertNotCompleted();
+    }
+
+    @Test
+    public void testNoInitialValueDoesNotEmitMultipleErrorEventsAndReportsSecondErrorToHooks() {
+        try {
+            final List<Throwable> list = new CopyOnWriteArrayList<Throwable>();
+            RxJavaHooks.setOnError(new Action1<Throwable>() {
+
+                @Override
+                public void call(Throwable t) {
+                    list.add(t);
+                }
+            });
+            TestSubscriber<Integer> ts = TestSubscriber.create();
+            final RuntimeException e1 = new RuntimeException("e1");
+            final Throwable e2 = new RuntimeException("e2");
+            Observable.create(new OnSubscribe<Integer>() {
+
+                @Override
+                public void call(final Subscriber<? super Integer> sub) {
+                    sub.setProducer(new Producer() {
+
+                        @Override
+                        public void request(long n) {
+                            if (n > 1) {
+                                sub.onNext(1);
+                                sub.onNext(2);
+                                sub.onError(e2);
+                            }
+                        }
+                    });
+                }
+            })
+            .reduce(new Func2<Integer, Integer, Integer>() {
+
+                @Override
+                public Integer call(Integer a, Integer b) {
+                    throw e1;
+            }})
+            .unsafeSubscribe(ts);
+            ts.assertNotCompleted();
+            System.out.println(ts.getOnErrorEvents());
+            assertEquals(Arrays.asList(e1), ts.getOnErrorEvents());
+            assertEquals(Arrays.asList(e2), list);
+        } finally {
+            RxJavaHooks.setOnError(null);
+        }
+    }
+
+
+    @Test
+    public void testNoInitialValueEmitsNoSuchElementExceptionIfEmptyStream() {
+        TestSubscriber<Integer> ts = TestSubscriber.create();
+        Observable.<Integer>empty().reduce(new Func2<Integer, Integer, Integer>() {
+
+            @Override
+            public Integer call(Integer a, Integer b) {
+                return a + b;
+            }
+        }).subscribe(ts);
+        ts.assertError(NoSuchElementException.class);
+    }
+
+
+}