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.observers;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.MaybeObserver;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Wraps another {@link MaybeObserver} and catches exceptions thrown by its
   * {@code onSubscribe}, {@code onSuccess}, {@code onError} or
   * {@code onComplete} methods despite the protocol forbids it.
   * <p>
   * Such exceptions are routed to the {@link RxJavaPlugins#onError(Throwable)} handler.
   *
   * @param <T> the element type of the sequence
   * @since 3.0.0
   */
  public final class SafeMaybeObserver<T> implements MaybeObserver<T> {
  
      final MaybeObserver<? super T> downstream;
  
      boolean onSubscribeFailed;
  
      public SafeMaybeObserver(MaybeObserver<? super T> downstream) {
          this.downstream = downstream;
      }
  
      @Override
      public void onSubscribe(@NonNull Disposable d) {
          try {
              downstream.onSubscribe(d);
          } catch (Throwable ex) {
              Exceptions.throwIfFatal(ex);
              onSubscribeFailed = true;
              d.dispose();
              RxJavaPlugins.onError(ex);
          }
      }
  
      @Override
      public void onSuccess(@NonNull T t) {
          if (!onSubscribeFailed) {
              try {
                  downstream.onSuccess(t);
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  RxJavaPlugins.onError(ex);
              }
          }
      }
  
      @Override
      public void onError(@NonNull Throwable e) {
          if (onSubscribeFailed) {
              RxJavaPlugins.onError(e);
          } else {
              try {
                  downstream.onError(e);
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  RxJavaPlugins.onError(new CompositeException(e, ex));
              }
          }
      }
  
      @Override
      public void onComplete() {
          if (!onSubscribeFailed) {
              try {
                  downstream.onComplete();
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  RxJavaPlugins.onError(ex);
              }
          }
      }
  }
  