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.flowable;
  
  import org.reactivestreams.Subscriber;
  
  import io.reactivex.rxjava3.core.Flowable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.internal.fuseable.CancellableQueueFuseable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Executes an {@link Action} and signals its exception or completes normally.
   *
   * @param <T> the value type
   * @since 3.0.0
   */
  public final class FlowableFromAction<T> extends Flowable<T> implements Supplier<T> {
  
      final Action action;
  
      public FlowableFromAction(Action action) {
          this.action = action;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> subscriber) {
          CancellableQueueFuseable<T> qs = new CancellableQueueFuseable<>();
          subscriber.onSubscribe(qs);
  
          if (!qs.isDisposed()) {
  
              try {
                  action.run();
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  if (!qs.isDisposed()) {
                      subscriber.onError(ex);
                  } else {
                      RxJavaPlugins.onError(ex);
                  }
                  return;
              }
  
              if (!qs.isDisposed()) {
                  subscriber.onComplete();
              }
          }
      }
  
      @Override
      public T get() throws Throwable {
          action.run();
          return null; // considered as onComplete()
      }
  }
  