code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * 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 io.reactivex.rxjava3.internal.operators.observable;
  
  import static org.junit.Assert.*;
  import static org.mockito.ArgumentMatchers.any;
  import static org.mockito.Mockito.*;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.disposables.Disposable;
  import org.junit.Test;
  import org.mockito.Mockito;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.TestException;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.observers.TestObserver;
  import io.reactivex.rxjava3.schedulers.Schedulers;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class ObservableOnErrorReturnTest extends RxJavaTest {
  
      @Test
      public void resumeNext() {
          TestObservable f = new TestObservable("one");
          Observable<String> w = Observable.unsafeCreate(f);
          final AtomicReference<Throwable> capturedException = new AtomicReference<>();
  
          Observable<String> observable = w.onErrorReturn(new Function<Throwable, String>() {
  
              @Override
              public String apply(Throwable e) {
                  capturedException.set(e);
                  return "failure";
              }
  
          });
  
          Observer<String> observer = TestHelper.mockObserver();
          observable.subscribe(observer);
  
          try {
              f.t.join();
          } catch (InterruptedException e) {
              fail(e.getMessage());
          }
  
          verify(observer, Mockito.never()).onError(any(Throwable.class));
          verify(observer, times(1)).onComplete();
          verify(observer, times(1)).onNext("one");
          verify(observer, times(1)).onNext("failure");
          assertNotNull(capturedException.get());
      }
  
      /**
       * Test that when a function throws an exception this is propagated through onError.
       */
      @Test
      public void functionThrowsError() {
          TestObservable f = new TestObservable("one");
          Observable<String> w = Observable.unsafeCreate(f);
          final AtomicReference<Throwable> capturedException = new AtomicReference<>();
  
          Observable<String> observable = w.onErrorReturn(new Function<Throwable, String>() {
  
              @Override
              public String apply(Throwable e) {
                  capturedException.set(e);
                  throw new RuntimeException("exception from function");
              }
  
          });
  
          Observer<String> observer = TestHelper.mockObserver();
          observable.subscribe(observer);
  
          try {
              f.t.join();
          } catch (InterruptedException e) {
              fail(e.getMessage());
          }
  
          // we should get the "one" value before the error
          verify(observer, times(1)).onNext("one");
  
          // we should have received an onError call on the Observer since the resume function threw an exception
          verify(observer, times(1)).onError(any(Throwable.class));
          verify(observer, times(0)).onComplete();
          assertNotNull(capturedException.get());
      }
  
      @Test
      public void mapResumeAsyncNext() {
          // Trigger multiple failures
          Observable<String> w = Observable.just("one", "fail", "two", "three", "fail");
  
          // Introduce map function that fails intermittently (Map does not prevent this when the Observer is a
          //  rx.operator incl onErrorResumeNextViaObservable)
          w = w.map(new Function<String, String>() {
              @Override
              public String apply(String s) {
                  if ("fail".equals(s)) {
                      throw new RuntimeException("Forced Failure");
                  }
                  System.out.println("BadMapper:" + s);
                  return s;
              }
          });
  
          Observable<String> observable = w.onErrorReturn(new Function<Throwable, String>() {
  
              @Override
              public String apply(Throwable t1) {
                  return "resume";
              }
  
          });
  
          Observer<String> observer = TestHelper.mockObserver();
          TestObserver<String> to = new TestObserver<>(observer);
          observable.subscribe(to);
          to.awaitDone(5, TimeUnit.SECONDS);
  
          verify(observer, Mockito.never()).onError(any(Throwable.class));
          verify(observer, times(1)).onComplete();
          verify(observer, times(1)).onNext("one");
          verify(observer, Mockito.never()).onNext("two");
          verify(observer, Mockito.never()).onNext("three");
          verify(observer, times(1)).onNext("resume");
      }
  
      @Test
      public void backpressure() {
          TestObserver<Integer> to = new TestObserver<>();
          Observable.range(0, 100000)
                  .onErrorReturn(new Function<Throwable, Integer>() {
  
                      @Override
                      public Integer apply(Throwable t1) {
                          return 1;
                      }
  
                  })
                  .observeOn(Schedulers.computation())
                  .map(new Function<Integer, Integer>() {
                      int c;
  
                      @Override
                      public Integer apply(Integer t1) {
                          if (c++ <= 1) {
                              // slow
                              try {
                                  Thread.sleep(500);
                              } catch (InterruptedException e) {
                                  e.printStackTrace();
                              }
                          }
                          return t1;
                      }
  
                  })
                  .subscribe(to);
          to.awaitDone(5, TimeUnit.SECONDS);
          to.assertNoErrors();
      }
  
      private static class TestObservable implements ObservableSource<String> {
  
          final String[] values;
          Thread t;
  
          TestObservable(String... values) {
              this.values = values;
          }
  
          @Override
          public void subscribe(final Observer<? super String> observer) {
              observer.onSubscribe(Disposable.empty());
              System.out.println("TestObservable subscribed to ...");
              t = new Thread(new Runnable() {
  
                  @Override
                  public void run() {
                      try {
                          System.out.println("running TestObservable thread");
                          for (String s : values) {
                              System.out.println("TestObservable onNext: " + s);
                              observer.onNext(s);
                          }
                          throw new RuntimeException("Forced Failure");
                      } catch (Throwable e) {
                          observer.onError(e);
                      }
                  }
  
              });
              System.out.println("starting TestObservable thread");
              t.start();
              System.out.println("done starting TestObservable thread");
          }
      }
  
      @Test
      public void returnItem() {
          Observable.error(new TestException())
          .onErrorReturnItem(1)
          .test()
          .assertResult(1);
      }
  
      @Test
      public void dispose() {
          TestHelper.checkDisposed(Observable.just(1).onErrorReturnItem(1));
      }
  
      @Test
      public void doubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeObservable(new Function<Observable<Object>, ObservableSource<Object>>() {
              @Override
              public ObservableSource<Object> apply(Observable<Object> f) throws Exception {
                  return f.onErrorReturnItem(1);
              }
          });
      }
  }
  