1.x: Add Completable.andThen(Single)

src/main/java/rx/Completable.java

@@ -1114,6 +1114,24 @@ public final <T> Observable<T> andThen(Observable<T> next) {
         requireNonNull(next);
         return next.delaySubscription(toObservable());
     }
+
+    /**
+     * Returns a Single which will subscribe to this Completable and once that is completed then
+     * will subscribe to the {@code next} Single. An error event from this Completable will be
+     * propagated to the downstream subscriber and will result in skipping the subscription of the
+     * Single.
+     * <dl>
+     *  <dt><b>Scheduler:</b></dt>
+     *  <dd>{@code andThen} does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     *
+     * @param next the Single to subscribe after this Completable is completed, not null
+     * @return Single that composes this Completable and next
+     */
+    public final <T> Single<T> andThen(Single<T> next) {
+        requireNonNull(next);
+        return next.delaySubscription(toObservable());
+    }
 
     /**
      * Concatenates this Completable with another Completable.

src/main/java/rx/Single.java

@@ -27,7 +27,6 @@
 import rx.internal.util.UtilityFunctions;
 import rx.observers.SafeSubscriber;
 import rx.observers.SerializedSubscriber;
-import rx.plugins.RxJavaObservableExecutionHook;
 import rx.plugins.RxJavaPlugins;
 import rx.plugins.RxJavaSingleExecutionHook;
 import rx.schedulers.Schedulers;
@@ -2671,4 +2670,28 @@ public static <T, Resource> Single<T> using(
         return create(new SingleOnSubscribeUsing<T, Resource>(resourceFactory, singleFactory, disposeAction, disposeEagerly));
     }
 
+    /**
+     * Returns a Single that delays the subscription to this Single
+     * until the Observable completes. In case the {@code onError} of the supplied observer throws,
+     * the exception will be propagated to the downstream subscriber
+     * and will result in skipping the subscription of this Single.
+     *
+     * <p>
+     * <dl>
+     *  <dt><b>Scheduler:</b></dt>
+     *  <dd>This method does not operate by default on a particular {@link Scheduler}.</dd>
+     * </dl>
+     *
+     * @param other the Observable that should trigger the subscription
+     *        to this Single.
+     * @return a Single that delays the subscription to this Single
+     *         until the Observable emits an element or completes normally.
+     */
+    @Experimental
+    public final Single<T> delaySubscription(Observable<?> other) {
+        if (other == null) {
+            throw new NullPointerException();
+        }
+        return create(new SingleOnSubscribeDelaySubscriptionOther<T>(this, other));
+    }
 }

src/main/java/rx/internal/operators/SingleOnSubscribeDelaySubscriptionOther.java

@@ -0,0 +1,91 @@
+/**
+ * Copyright 2014 Netflix, 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 rx.internal.operators;
+
+import rx.Observable;
+import rx.Single;
+import rx.SingleSubscriber;
+import rx.Subscriber;
+import rx.plugins.RxJavaPlugins;
+import rx.subscriptions.SerialSubscription;
+
+/**
+ * Delays the subscription to the Single until the Observable
+ * fires an event or completes.
+ *
+ * @param <T> the Single value type
+ */
+public final class SingleOnSubscribeDelaySubscriptionOther<T> implements Single.OnSubscribe<T> {
+    final Single<? extends T> main;
+    final Observable<?> other;
+
+    public SingleOnSubscribeDelaySubscriptionOther(Single<? extends T> main, Observable<?> other) {
+        this.main = main;
+        this.other = other;
+    }
+
+    @Override
+    public void call(final SingleSubscriber<? super T> subscriber) {
+        final SingleSubscriber<T> child = new SingleSubscriber<T>() {
+            @Override
+            public void onSuccess(T value) {
+                subscriber.onSuccess(value);
+            }
+
+            @Override
+            public void onError(Throwable error) {
+                subscriber.onError(error);
+            }
+        };
+
+        final SerialSubscription serial = new SerialSubscription();
+        subscriber.add(serial);
+
+        Subscriber<Object> otherSubscriber = new Subscriber<Object>() {
+            boolean done;
+            @Override
+            public void onNext(Object t) {
+                onCompleted();
+            }
+
+            @Override
+            public void onError(Throwable e) {
+                if (done) {
+                    RxJavaPlugins.getInstance().getErrorHandler().handleError(e);
+                    return;
+                }
+                done = true;
+                child.onError(e);
+            }
+
+            @Override
+            public void onCompleted() {
+                if (done) {
+                    return;
+                }
+                done = true;
+                serial.set(child);
+
+                main.subscribe(child);
+            }
+        };
+
+        serial.set(otherSubscriber);
+
+        other.subscribe(otherSubscriber);
+    }
+}

src/test/java/rx/CompletableTest.java

@@ -418,6 +418,61 @@ public void andThenSubscribeOn() {
         ts.assertCompleted();
         ts.assertNoErrors();
     }
+
+    @Test
+    public void andThenSingle() {
+        TestSubscriber<String> ts = new TestSubscriber<String>(0);
+        Completable.complete().andThen(Single.just("foo")).subscribe(ts);
+        ts.requestMore(1);
+        ts.assertValue("foo");
+        ts.assertCompleted();
+        ts.assertNoErrors();
+        ts.assertUnsubscribed();
+    }
+
+    @Test
+    public void andThenSingleNever() {
+        TestSubscriber<String> ts = new TestSubscriber<String>(0);
+        Completable.never().andThen(Single.just("foo")).subscribe(ts);
+        ts.requestMore(1);
+        ts.assertNoValues();
+        ts.assertNoTerminalEvent();
+    }
+
+    @Test
+    public void andThenSingleError() {
+        TestSubscriber<String> ts = new TestSubscriber<String>(0);
+        final AtomicBoolean hasRun = new AtomicBoolean(false);
+        final Exception e = new Exception();
+        Completable.error(e)
+            .andThen(Single.<String>create(new Single.OnSubscribe<String>() {
+                @Override
+                public void call(SingleSubscriber<? super String> s) {
+                    hasRun.set(true);
+                    s.onSuccess("foo");
+                }
+            }))
+            .subscribe(ts);
+        ts.assertNoValues();
+        ts.assertError(e);
+        ts.assertUnsubscribed();
+        Assert.assertFalse("Should not have subscribed to single when completable errors", hasRun.get());
+    }
+
+    @Test
+    public void andThenSingleSubscribeOn() {
+        TestSubscriber<String> ts = new TestSubscriber<String>(0);
+        TestScheduler scheduler = new TestScheduler();
+        Completable.complete().andThen(Single.just("foo").delay(1, TimeUnit.SECONDS, scheduler)).subscribe(ts);
+        ts.requestMore(1);
+        ts.assertNoValues();
+        ts.assertNoTerminalEvent();
+        scheduler.advanceTimeBy(1, TimeUnit.SECONDS);
+        ts.assertValue("foo");
+        ts.assertCompleted();
+        ts.assertNoErrors();
+        ts.assertUnsubscribed();
+    }
 
     @Test(expected = NullPointerException.class)
     public void createNull() {

src/test/java/rx/internal/operators/SingleOnSubscribeDelaySubscriptionOtherTest.java

@@ -0,0 +1,112 @@
+package rx.internal.operators;
+
+import org.junit.Assert;
+import org.junit.Test;
+import rx.Single;
+import rx.exceptions.TestException;
+import rx.functions.Action0;
+import rx.observers.TestSubscriber;
+import rx.subjects.PublishSubject;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class SingleOnSubscribeDelaySubscriptionOtherTest {
+    @Test
+    public void noPrematureSubscription() {
+        PublishSubject<Object> other = PublishSubject.create();
+
+        TestSubscriber<Integer> ts = TestSubscriber.create();
+
+        final AtomicInteger subscribed = new AtomicInteger();
+
+        Single.just(1)
+            .doOnSubscribe(new Action0() {
+                @Override
+                public void call() {
+                    subscribed.getAndIncrement();
+                }
+            })
+            .delaySubscription(other)
+            .subscribe(ts);
+
+        ts.assertNotCompleted();
+        ts.assertNoErrors();
+        ts.assertNoValues();
+
+        Assert.assertEquals("Premature subscription", 0, subscribed.get());
+
+        other.onNext(1);
+
+        Assert.assertEquals("No subscription", 1, subscribed.get());
+
+        ts.assertValue(1);
+        ts.assertNoErrors();
+        ts.assertCompleted();
+    }
+
+    @Test
+    public void noPrematureSubscriptionToError() {
+        PublishSubject<Object> other = PublishSubject.create();
+
+        TestSubscriber<Integer> ts = TestSubscriber.create();
+
+        final AtomicInteger subscribed = new AtomicInteger();
+
+        Single.<Integer>error(new TestException())
+            .doOnSubscribe(new Action0() {
+                    @Override
+                    public void call() {
+                        subscribed.getAndIncrement();
+                    }
+                })
+            .delaySubscription(other)
+            .subscribe(ts);
+
+        ts.assertNotCompleted();
+        ts.assertNoErrors();
+        ts.assertNoValues();
+
+        Assert.assertEquals("Premature subscription", 0, subscribed.get());
+
+        other.onNext(1);
+
+        Assert.assertEquals("No subscription", 1, subscribed.get());
+
+        ts.assertNoValues();
+        ts.assertNotCompleted();
+        ts.assertError(TestException.class);
+    }
+
+    @Test
+    public void noSubscriptionIfOtherErrors() {
+        PublishSubject<Object> other = PublishSubject.create();
+
+        TestSubscriber<Integer> ts = TestSubscriber.create();
+
+        final AtomicInteger subscribed = new AtomicInteger();
+
+        Single.<Integer>error(new TestException())
+            .doOnSubscribe(new Action0() {
+                    @Override
+                    public void call() {
+                        subscribed.getAndIncrement();
+                    }
+                })
+            .delaySubscription(other)
+            .subscribe(ts);
+
+        ts.assertNotCompleted();
+        ts.assertNoErrors();
+        ts.assertNoValues();
+
+        Assert.assertEquals("Premature subscription", 0, subscribed.get());
+
+        other.onError(new TestException());
+
+        Assert.assertEquals("Premature subscription", 0, subscribed.get());
+
+        ts.assertNoValues();
+        ts.assertNotCompleted();
+        ts.assertError(TestException.class);
+    }
+}