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 static org.junit.Assert.assertEquals;
  import static org.mockito.ArgumentMatchers.any;
  import static org.mockito.Mockito.*;
  
  import java.util.List;
  import java.util.concurrent.CountDownLatch;
  
  import org.junit.Test;
  import org.mockito.invocation.InvocationOnMock;
  import org.mockito.stubbing.Answer;
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.TestException;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  import io.reactivex.rxjava3.schedulers.Schedulers;
  import io.reactivex.rxjava3.subscribers.TestSubscriber;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class FlowableFromSupplierTest extends RxJavaTest {
  
      @SuppressWarnings("unchecked")
      @Test
      public void shouldNotInvokeFuncUntilSubscription() throws Throwable {
          Supplier<Object> func = mock(Supplier.class);
  
          when(func.get()).thenReturn(new Object());
  
          Flowable<Object> fromSupplierFlowable = Flowable.fromSupplier(func);
  
          verifyNoInteractions(func);
  
          fromSupplierFlowable.subscribe();
  
          verify(func).get();
      }
  
      @SuppressWarnings("unchecked")
      @Test
      public void shouldCallOnNextAndOnCompleted() throws Throwable {
          Supplier<String> func = mock(Supplier.class);
  
          when(func.get()).thenReturn("test_value");
  
          Flowable<String> fromSupplierFlowable = Flowable.fromSupplier(func);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
  
          fromSupplierFlowable.subscribe(subscriber);
  
          verify(subscriber).onNext("test_value");
          verify(subscriber).onComplete();
          verify(subscriber, never()).onError(any(Throwable.class));
      }
  
      @SuppressWarnings("unchecked")
      @Test
      public void shouldCallOnError() throws Throwable {
          Supplier<Object> func = mock(Supplier.class);
  
          Throwable throwable = new IllegalStateException("Test exception");
          when(func.get()).thenThrow(throwable);
  
          Flowable<Object> fromSupplierFlowable = Flowable.fromSupplier(func);
  
          Subscriber<Object> subscriber = TestHelper.mockSubscriber();
  
          fromSupplierFlowable.subscribe(subscriber);
  
          verify(subscriber, never()).onNext(any());
          verify(subscriber, never()).onComplete();
          verify(subscriber).onError(throwable);
      }
  
      @SuppressWarnings("unchecked")
      @Test
      public void shouldNotDeliverResultIfSubscriberUnsubscribedBeforeEmission() throws Throwable {
          Supplier<String> func = mock(Supplier.class);
  
          final CountDownLatch funcLatch = new CountDownLatch(1);
          final CountDownLatch observerLatch = new CountDownLatch(1);
  
          when(func.get()).thenAnswer(new Answer<String>() {
              @Override
              public String answer(InvocationOnMock invocation) throws Throwable {
                  observerLatch.countDown();
  
                  try {
                      funcLatch.await();
                  } catch (InterruptedException e) {
                      // It's okay, unsubscription causes Thread interruption
  
                      // Restoring interruption status of the Thread
                      Thread.currentThread().interrupt();
                  }
  
                  return "should_not_be_delivered";
              }
          });
  
          Flowable<String> fromSupplierFlowable = Flowable.fromSupplier(func);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
  
          TestSubscriber<String> outer = new TestSubscriber<>(subscriber);
  
          fromSupplierFlowable
                  .subscribeOn(Schedulers.computation())
                  .subscribe(outer);
  
          // Wait until func will be invoked
          observerLatch.await();
  
          // Unsubscribing before emission
          outer.cancel();
  
          // Emitting result
          funcLatch.countDown();
  
          // func must be invoked
          verify(func).get();
  
          // Observer must not be notified at all
          verify(subscriber).onSubscribe(any(Subscription.class));
          verifyNoMoreInteractions(subscriber);
      }
  
      @Test
      public void shouldAllowToThrowCheckedException() {
          final Exception checkedException = new Exception("test exception");
  
          Flowable<Object> fromSupplierFlowable = Flowable.fromSupplier(new Supplier<Object>() {
              @Override
              public Object get() throws Exception {
                  throw checkedException;
              }
          });
  
          Subscriber<Object> subscriber = TestHelper.mockSubscriber();
  
          fromSupplierFlowable.subscribe(subscriber);
  
          verify(subscriber).onSubscribe(any(Subscription.class));
          verify(subscriber).onError(checkedException);
          verifyNoMoreInteractions(subscriber);
      }
  
      @Test
      public void fusedFlatMapExecution() {
          final int[] calls = { 0 };
  
          Flowable.just(1).flatMap(new Function<Integer, Publisher<? extends Object>>() {
              @Override
              public Publisher<? extends Object> apply(Integer v)
                      throws Exception {
                  return Flowable.fromSupplier(new Supplier<Object>() {
                      @Override
                      public Object get() throws Exception {
                          return ++calls[0];
                      }
                  });
              }
          })
          .test()
          .assertResult(1);
  
          assertEquals(1, calls[0]);
      }
  
      @Test
      public void fusedFlatMapExecutionHidden() {
          final int[] calls = { 0 };
  
          Flowable.just(1).hide().flatMap(new Function<Integer, Publisher<? extends Object>>() {
              @Override
              public Publisher<? extends Object> apply(Integer v)
                      throws Exception {
                  return Flowable.fromSupplier(new Supplier<Object>() {
                      @Override
                      public Object get() throws Exception {
                          return ++calls[0];
                      }
                  });
              }
          })
          .test()
          .assertResult(1);
  
          assertEquals(1, calls[0]);
      }
  
      @Test
      public void fusedFlatMapNull() {
          Flowable.just(1).flatMap(new Function<Integer, Publisher<? extends Object>>() {
              @Override
              public Publisher<? extends Object> apply(Integer v)
                      throws Exception {
                  return Flowable.fromSupplier(new Supplier<Object>() {
                      @Override
                      public Object get() throws Exception {
                          return null;
                      }
                  });
              }
          })
          .test()
          .assertFailure(NullPointerException.class);
      }
  
      @Test
      public void fusedFlatMapNullHidden() {
          Flowable.just(1).hide().flatMap(new Function<Integer, Publisher<? extends Object>>() {
              @Override
              public Publisher<? extends Object> apply(Integer v)
                      throws Exception {
                  return Flowable.fromSupplier(new Supplier<Object>() {
                      @Override
                      public Object get() throws Exception {
                          return null;
                      }
                  });
              }
          })
          .test()
          .assertFailure(NullPointerException.class);
      }
  
      @Test
      public void undeliverableUponCancellation() throws Exception {
          List<Throwable> errors = TestHelper.trackPluginErrors();
          try {
              final TestSubscriber<Integer> ts = new TestSubscriber<>();
  
              Flowable.fromSupplier(new Supplier<Integer>() {
                  @Override
                  public Integer get() throws Exception {
                      ts.cancel();
                      throw new TestException();
                  }
              })
              .subscribe(ts);
  
              ts.assertEmpty();
  
              TestHelper.assertUndeliverable(errors, 0, TestException.class);
          } finally {
              RxJavaPlugins.reset();
          }
      }
  }
  