catch onCompleted unsubscribe error and report to RxJavaPlugin error handler

Author: davidmoten

src/main/java/rx/exceptions/OnCompletedFailedException.java

@@ -0,0 +1,29 @@
+/**
+ * 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.exceptions;
+
+public final class OnCompletedFailedException extends RuntimeException {
+
+    private static final long serialVersionUID = 8622579378868820554L;
+
+    public OnCompletedFailedException(Throwable throwable) {
+        super(throwable);
+    }
+    
+    public OnCompletedFailedException(String message, Throwable throwable) {
+        super(message, throwable);
+    }
+}

src/main/java/rx/exceptions/UnsubscribeFailedException.java

@@ -0,0 +1,30 @@
+/**
+ * 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.exceptions;
+
+public final class UnsubscribeFailedException extends RuntimeException {
+
+    private static final long serialVersionUID = 4594672310593167598L;
+
+    public UnsubscribeFailedException(Throwable throwable) {
+        super(throwable);
+    }
+    
+    public UnsubscribeFailedException(String message, Throwable throwable) {
+        super(message, throwable);
+    }
+    
+}

src/main/java/rx/internal/util/RxJavaPluginUtils.java

@@ -0,0 +1,40 @@
+/**
+ * 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.util;
+
+import rx.plugins.RxJavaPlugins;
+
+public final class RxJavaPluginUtils {
+
+    public static void handleException(Throwable e) {
+        try {
+            RxJavaPlugins.getInstance().getErrorHandler().handleError(e);
+        } catch (Throwable pluginException) {
+            handlePluginException(pluginException);
+        }
+    }
+
+    private static void handlePluginException(Throwable pluginException) {
+        /*
+         * We don't want errors from the plugin to affect normal flow.
+         * Since the plugin should never throw this is a safety net
+         * and will complain loudly to System.err so it gets fixed.
+         */
+        System.err.println("RxJavaErrorHandler threw an Exception. It shouldn't. => " + pluginException.getMessage());
+        pluginException.printStackTrace();
+    }
+    
+}

src/main/java/rx/observers/SafeSubscriber.java

@@ -20,9 +20,11 @@
 import rx.Subscriber;
 import rx.exceptions.CompositeException;
 import rx.exceptions.Exceptions;
+import rx.exceptions.OnCompletedFailedException;
 import rx.exceptions.OnErrorFailedException;
 import rx.exceptions.OnErrorNotImplementedException;
-import rx.plugins.RxJavaPlugins;
+import rx.exceptions.UnsubscribeFailedException;
+import rx.internal.util.RxJavaPluginUtils;
 
 /**
  * {@code SafeSubscriber} is a wrapper around {@code Subscriber} that ensures that the {@code Subscriber}
@@ -83,11 +85,17 @@ public void onCompleted() {
                 // we handle here instead of another method so we don't add stacks to the frame
                 // which can prevent it from being able to handle StackOverflow
                 Exceptions.throwIfFatal(e);
-                // handle errors if the onCompleted implementation fails, not just if the Observable fails
-                _onError(e);
+                RxJavaPluginUtils.handleException(e);
+                throw new OnCompletedFailedException(e.getMessage(), e);
             } finally {
-                // auto-unsubscribe
-                unsubscribe();
+                try {
+                    // Similarly to onError if failure occurs in unsubscribe then Rx contract is broken
+                    // and we throw an UnsubscribeFailureException.
+                    unsubscribe();
+                } catch (Throwable e) {
+                    RxJavaPluginUtils.handleException(e);
+                    throw new UnsubscribeFailedException(e.getMessage(), e);
+                }
             }
         }
     }
@@ -145,11 +153,7 @@ public void onNext(T args) {
      * @see <a href="https://github.com/ReactiveX/RxJava/issues/630">the report of this bug</a>
      */
     protected void _onError(Throwable e) {
-        try {
-            RxJavaPlugins.getInstance().getErrorHandler().handleError(e);
-        } catch (Throwable pluginException) {
-            handlePluginException(pluginException);
-        }
+        RxJavaPluginUtils.handleException(e);
         try {
             actual.onError(e);
         } catch (Throwable e2) {
@@ -168,11 +172,7 @@ protected void _onError(Throwable e) {
                 try {
                     unsubscribe();
                 } catch (Throwable unsubscribeException) {
-                    try {
-                        RxJavaPlugins.getInstance().getErrorHandler().handleError(unsubscribeException);
-                    } catch (Throwable pluginException) {
-                        handlePluginException(pluginException);
-                    }
+                    RxJavaPluginUtils.handleException(unsubscribeException);
                     throw new RuntimeException("Observer.onError not implemented and error while unsubscribing.", new CompositeException(Arrays.asList(e, unsubscribeException)));
                 }
                 throw (OnErrorNotImplementedException) e2;
@@ -182,19 +182,11 @@ protected void _onError(Throwable e) {
                  * 
                  * https://github.com/ReactiveX/RxJava/issues/198
                  */
-                try {
-                    RxJavaPlugins.getInstance().getErrorHandler().handleError(e2);
-                } catch (Throwable pluginException) {
-                    handlePluginException(pluginException);
-                }
+                RxJavaPluginUtils.handleException(e2);
                 try {
                     unsubscribe();
                 } catch (Throwable unsubscribeException) {
-                    try {
-                        RxJavaPlugins.getInstance().getErrorHandler().handleError(unsubscribeException);
-                    } catch (Throwable pluginException) {
-                        handlePluginException(pluginException);
-                    }
+                    RxJavaPluginUtils.handleException(unsubscribeException);
                     throw new OnErrorFailedException("Error occurred when trying to propagate error to Observer.onError and during unsubscription.", new CompositeException(Arrays.asList(e, e2, unsubscribeException)));
                 }
 
@@ -205,25 +197,11 @@ protected void _onError(Throwable e) {
         try {
             unsubscribe();
         } catch (RuntimeException unsubscribeException) {
-            try {
-                RxJavaPlugins.getInstance().getErrorHandler().handleError(unsubscribeException);
-            } catch (Throwable pluginException) {
-                handlePluginException(pluginException);
-            }
+            RxJavaPluginUtils.handleException(unsubscribeException);
             throw new OnErrorFailedException(unsubscribeException);
         }
     }
 
-    private void handlePluginException(Throwable pluginException) {
-        /*
-         * We don't want errors from the plugin to affect normal flow.
-         * Since the plugin should never throw this is a safety net
-         * and will complain loudly to System.err so it gets fixed.
-         */
-        System.err.println("RxJavaErrorHandler threw an Exception. It shouldn't. => " + pluginException.getMessage());
-        pluginException.printStackTrace();
-    }
-
     /**
      * Returns the {@link Subscriber} underlying this {@code SafeSubscriber}.
      *

src/test/java/rx/observers/SafeObserverTest.java

@@ -22,6 +22,7 @@
 
 import org.junit.Test;
 
+import junit.framework.Assert;
 import rx.Subscriber;
 import rx.exceptions.*;
 import rx.functions.Action0;
@@ -68,19 +69,6 @@ public void onCompletedFailure() {
         }
     }
 
-    @Test
-    public void onCompletedFailureSafe() {
-        AtomicReference<Throwable> onError = new AtomicReference<Throwable>();
-        try {
-            new SafeSubscriber<String>(OBSERVER_ONCOMPLETED_FAIL(onError)).onCompleted();
-            assertNotNull(onError.get());
-            assertTrue(onError.get() instanceof SafeObserverTestException);
-            assertEquals("onCompletedFail", onError.get().getMessage());
-        } catch (Exception e) {
-            fail("expects exception to be passed to onError");
-        }
-    }
-
     @Test
     public void onErrorFailure() {
         try {
@@ -184,8 +172,8 @@ public void call() {
             e.printStackTrace();
 
             assertTrue(o.isUnsubscribed());
-
-            assertTrue(e instanceof SafeObserverTestException);
+            assertTrue(e instanceof UnsubscribeFailedException);
+            assertTrue(e.getCause() instanceof SafeObserverTestException);
             assertEquals("failure from unsubscribe", e.getMessage());
             // expected since onError fails so SafeObserver can't help
         }
@@ -475,9 +463,12 @@ public void onCompleted() {
             }
         });
 
-        s.onCompleted();
-        
-        assertTrue("Error not received", error.get() instanceof TestException);
+        try {
+            s.onCompleted();
+            Assert.fail();
+        } catch (OnCompletedFailedException e) {
+           assertNull(error.get());
+        }
     }
 
     @Test