fix error handling in onBackpressureBuffer

Author: davidmoten

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

@@ -22,6 +22,7 @@
 import rx.Observable.Operator;
 import rx.Producer;
 import rx.Subscriber;
+import rx.exceptions.Exceptions;
 import rx.exceptions.MissingBackpressureException;
 import rx.functions.Action0;
 import rx.internal.util.BackpressureDrainManager;
@@ -156,7 +157,15 @@ private boolean assertCapacity() {
                                 "Overflowed buffer of "
                                         + baseCapacity));
                         if (onOverflow != null) {
-                            onOverflow.call();
+                            try {
+                                onOverflow.call();
+                            } catch (Throwable e) {
+                                Exceptions.throwIfFatal(e);
+                                manager.terminateAndDrain(e);
+                                // this line not strictly necessary but nice for clarity
+                                // and in case of future changes to code after this catch block 
+                                return false;
+                            }
                         }
                     }
                     return false;

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

@@ -15,10 +15,17 @@
  */
 package rx.internal.operators;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.Mockito;
 
 import rx.Observable;
 import rx.Observable.OnSubscribe;
@@ -27,12 +34,10 @@
 import rx.Subscription;
 import rx.exceptions.MissingBackpressureException;
 import rx.functions.Action0;
+import rx.functions.Action1;
 import rx.observers.TestSubscriber;
 import rx.schedulers.Schedulers;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-
 public class OperatorOnBackpressureBufferTest {
 
     @Test
@@ -147,5 +152,30 @@ public void call(Subscriber<? super Long> s) {
         }
 
     });
+    
+    private static final Action0 THROWS_NON_FATAL = new Action0() {
+
+        @Override
+        public void call() {
+            throw new RuntimeException();
+        }}; 
+    
+    @Test
+    public void testNonFatalExceptionThrownByOnOverflowIsNotReportedByUpstream() {
+         final AtomicBoolean errorOccurred = new AtomicBoolean(false);
+         TestSubscriber<Long> ts = TestSubscriber.create(0);
+         infinite
+           .subscribeOn(Schedulers.computation())
+           .doOnError(new Action1<Throwable>() {
+                 @Override
+                 public void call(Throwable t) {
+                     errorOccurred.set(true);
+                 }
+             })
+           .onBackpressureBuffer(1, THROWS_NON_FATAL)
+           .subscribe(ts);
+         ts.awaitTerminalEvent();
+         assertFalse(errorOccurred.get());
+    }
 
 }