fix error handling in OperatorDistinctUntilChanged

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

@@ -17,6 +17,7 @@
 
 import rx.Observable.Operator;
 import rx.Subscriber;
+import rx.exceptions.Exceptions;
 import rx.functions.Func1;
 import rx.internal.util.UtilityFunctions;
 
@@ -56,7 +57,13 @@ public Subscriber<? super T> call(final Subscriber<? super T> child) {
             @Override
             public void onNext(T t) {
                 U currentKey = previousKey;
-                U key = keySelector.call(t);
+                final U key;
+                try {
+                    key = keySelector.call(t);
+                } catch (Throwable e) {
+                    Exceptions.throwOrReport(e, child, t);
+                    return;
+                }
                 previousKey = key;
 
                 if (hasPrevious) {

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

@@ -15,6 +15,7 @@
  */
 package rx.internal.operators;
 
+import static org.junit.Assert.assertFalse;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyString;
 import static org.mockito.Mockito.inOrder;
@@ -23,6 +24,7 @@
 import static org.mockito.Mockito.verify;
 import static org.mockito.MockitoAnnotations.initMocks;
 
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -31,17 +33,18 @@
 
 import rx.Observable;
 import rx.Observer;
+import rx.functions.Action1;
 import rx.functions.Func1;
 
 public class OperatorDistinctUntilChangedTest {
 
     @Mock
-    Observer<String> w;
+    private Observer<String> w;
     @Mock
-    Observer<String> w2;
+    private Observer<String> w2;
 
     // nulls lead to exceptions
-    final Func1<String, String> TO_UPPER_WITH_EXCEPTION = new Func1<String, String>() {
+    private final static Func1<String, String> TO_UPPER_WITH_EXCEPTION = new Func1<String, String>() {
         @Override
         public String call(String s) {
             if (s.equals("x")) {
@@ -50,6 +53,13 @@ public String call(String s) {
             return s.toUpperCase();
         }
     };
+
+    private final static Func1<String, String> THROWS_NON_FATAL = new Func1<String, String>() {
+        @Override
+        public String call(String s) {
+            throw new RuntimeException();
+        }
+    };
 
     @Before
     public void before() {
@@ -138,4 +148,20 @@ public void testDistinctUntilChangedOfSourceWithExceptionsFromKeySelector() {
         inOrder.verify(w, never()).onNext(anyString());
         inOrder.verify(w, never()).onCompleted();
     }
+
+    @Test
+    public void testDistinctUntilChangedWhenNonFatalExceptionThrownByKeySelectorIsNotReportedByUpstream() {
+        Observable<String> src = Observable.just("a", "b", null, "c");
+        final AtomicBoolean errorOccurred = new AtomicBoolean(false);
+        src
+          .doOnError(new Action1<Throwable>() {
+                @Override
+                public void call(Throwable t) {
+                    errorOccurred.set(true);
+                }
+            })
+          .distinctUntilChanged(THROWS_NON_FATAL)
+          .subscribe(w);
+        assertFalse(errorOccurred.get());
+    }
 }