Implement proper error handling for Rx types.

Since we've implemented our own observables instead of using the built-in factories we have to do the heavy lifting of these edge cases ourselves.

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/BodyOnSubscribe.java

@@ -18,6 +18,8 @@
 import retrofit2.Response;
 import rx.Observable.OnSubscribe;
 import rx.Subscriber;
+import rx.exceptions.CompositeException;
+import rx.plugins.RxJavaPlugins;
 
 final class BodyOnSubscribe<T> implements OnSubscribe<T> {
   private final OnSubscribe<Response<T>> upstream;
@@ -45,15 +47,27 @@ private static class BodySubscriber<R> extends Subscriber<Response<R>> {
         subscriber.onNext(response.body());
       } else {
         subscriberTerminated = true;
-        subscriber.onError(new HttpException(response));
+        Throwable t = new HttpException(response);
+        try {
+          subscriber.onError(t);
+        } catch (Throwable inner) {
+          CompositeException composite = new CompositeException(t, inner);
+          RxJavaPlugins.getInstance().getErrorHandler().handleError(composite);
+        }
       }
     }
 
     @Override public void onError(Throwable throwable) {
       if (!subscriberTerminated) {
         subscriber.onError(throwable);
+      } else {
+        // This should never happen! onNext handles and forwards errors automatically.
+        Throwable broken = new AssertionError(
+            "This should never happen! Report as a Retrofit bug with the full stacktrace.");
+        //noinspection UnnecessaryInitCause Two-arg AssertionError constructor is 1.7+ only.
+        broken.initCause(throwable);
+        RxJavaPlugins.getInstance().getErrorHandler().handleError(broken);
       }
-      // TODO else send to plugin as unhandled error
     }
 
     @Override public void onCompleted() {

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/CallOnSubscribe.java

@@ -22,7 +22,9 @@
 import rx.Producer;
 import rx.Subscriber;
 import rx.Subscription;
+import rx.exceptions.CompositeException;
 import rx.exceptions.Exceptions;
+import rx.plugins.RxJavaPlugins;
 
 final class CallOnSubscribe<T> implements OnSubscribe<Response<T>> {
   private final Call<T> originalCall;
@@ -62,18 +64,27 @@ private static final class CallArbiter<T> extends AtomicBoolean
         return;
       }
 
+      boolean terminated = false;
       try {
         Response<T> response = call.execute();
         if (!call.isCanceled()) {
           subscriber.onNext(response);
         }
         if (!call.isCanceled()) {
+          terminated = true;
           subscriber.onCompleted();
         }
       } catch (Throwable t) {
         Exceptions.throwIfFatal(t);
-        if (!call.isCanceled()) {
-          subscriber.onError(t);
+        if (terminated) {
+          RxJavaPlugins.getInstance().getErrorHandler().handleError(t);
+        } else if (!call.isCanceled()) {
+          try {
+            subscriber.onError(t);
+          } catch (Throwable inner) {
+            CompositeException composite = new CompositeException(t, inner);
+            RxJavaPlugins.getInstance().getErrorHandler().handleError(composite);
+          }
         }
       }
     }

retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/ResultOnSubscribe.java

@@ -18,6 +18,8 @@
 import retrofit2.Response;
 import rx.Observable.OnSubscribe;
 import rx.Subscriber;
+import rx.exceptions.CompositeException;
+import rx.plugins.RxJavaPlugins;
 
 final class ResultOnSubscribe<T> implements OnSubscribe<Result<T>> {
   private final OnSubscribe<Response<T>> upstream;
@@ -46,7 +48,12 @@ private static class ResultSubscriber<R> extends Subscriber<Response<R>> {
       try {
         subscriber.onNext(Result.<R>error(throwable));
       } catch (Throwable t) {
-        subscriber.onError(t);
+        try {
+          subscriber.onError(t);
+        } catch (Throwable inner) {
+          CompositeException composite = new CompositeException(t, inner);
+          RxJavaPlugins.getInstance().getErrorHandler().handleError(composite);
+        }
         return;
       }
       subscriber.onCompleted();

retrofit-adapters/rxjava/src/test/java/retrofit2/adapter/rxjava/CompletableTest.java

@@ -16,20 +16,27 @@
 package retrofit2.adapter.rxjava;
 
 import java.io.IOException;
+import java.util.concurrent.atomic.AtomicReference;
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TestRule;
 import retrofit2.Retrofit;
 import retrofit2.http.GET;
 import rx.Completable;
+import rx.exceptions.CompositeException;
+import rx.exceptions.Exceptions;
+import rx.plugins.RxJavaErrorHandler;
+import rx.plugins.RxJavaPlugins;
 
 import static okhttp3.mockwebserver.SocketPolicy.DISCONNECT_AFTER_REQUEST;
 import static org.assertj.core.api.Assertions.assertThat;
 
 public final class CompletableTest {
   @Rule public final MockWebServer server = new MockWebServer();
+  @Rule public final TestRule pluginsReset = new RxJavaPluginsResetRule();
   @Rule public final RecordingSubscriber.Rule subscriberRule = new RecordingSubscriber.Rule();
 
   interface Service {
@@ -69,4 +76,56 @@ interface Service {
     service.completable().unsafeSubscribe(subscriber);
     subscriber.assertError(IOException.class);
   }
+
+  @Test public void bodyThrowingInOnCompletedDeliveredToPlugin() {
+    server.enqueue(new MockResponse().setBody("Hi"));
+
+    final AtomicReference<Throwable> throwableRef = new AtomicReference<>();
+    RxJavaPlugins.getInstance().registerErrorHandler(new RxJavaErrorHandler() {
+      @Override public void handleError(Throwable throwable) {
+        if (!throwableRef.compareAndSet(null, throwable)) {
+          throw Exceptions.propagate(throwable);
+        }
+      }
+    });
+
+    RecordingSubscriber<String> subscriber = subscriberRule.create();
+    final RuntimeException e = new RuntimeException();
+    service.completable().unsafeSubscribe(new ForwardingSubscriber<String>(subscriber) {
+      @Override public void onCompleted() {
+        throw e;
+      }
+    });
+
+    assertThat(throwableRef.get()).isSameAs(e);
+  }
+
+  @Test public void bodyThrowingInOnErrorDeliveredToPlugin() {
+    server.enqueue(new MockResponse().setResponseCode(404));
+
+    final AtomicReference<Throwable> throwableRef = new AtomicReference<>();
+    RxJavaPlugins.getInstance().registerErrorHandler(new RxJavaErrorHandler() {
+      @Override public void handleError(Throwable throwable) {
+        if (!throwableRef.compareAndSet(null, throwable)) {
+          throw Exceptions.propagate(throwable);
+        }
+      }
+    });
+
+    RecordingSubscriber<String> subscriber = subscriberRule.create();
+    final AtomicReference<Throwable> errorRef = new AtomicReference<>();
+    final RuntimeException e = new RuntimeException();
+    service.completable().unsafeSubscribe(new ForwardingSubscriber<String>(subscriber) {
+      @Override public void onError(Throwable throwable) {
+        if (!errorRef.compareAndSet(null, throwable)) {
+          throw Exceptions.propagate(throwable);
+        }
+        throw e;
+      }
+    });
+
+    //noinspection ThrowableResultOfMethodCallIgnored
+    CompositeException composite = (CompositeException) throwableRef.get();
+    assertThat(composite.getExceptions()).containsExactly(errorRef.get(), e);
+  }
 }

retrofit-adapters/rxjava/src/test/java/retrofit2/adapter/rxjava/ForwardingSubscriber.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2016 Square, 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 retrofit2.adapter.rxjava;
+
+import rx.Subscriber;
+
+abstract class ForwardingSubscriber<T> extends Subscriber<T> {
+  private final Subscriber<T> delegate;
+
+  ForwardingSubscriber(Subscriber<T> delegate) {
+    this.delegate = delegate;
+  }
+
+  @Override public void onNext(T value) {
+    delegate.onNext(value);
+  }
+
+  @Override public void onCompleted() {
+    delegate.onCompleted();
+  }
+
+  @Override public void onError(Throwable throwable) {
+    delegate.onError(throwable);
+  }
+}