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Support blocking with: scalaFuture.toJava.toCompletableFuture #49

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Merged
merged 8 commits into from
Aug 18, 2015
Merged

Support blocking with: scalaFuture.toJava.toCompletableFuture #49

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7bc38cb
Support blocking with: `scalaFuture.toJava.toCompletableFuture`
retronym Jul 28, 2015
46d8b30
Test case for toJava / thenCompose that now works
retronym Jul 28, 2015
9cb51e6
Extra test and comment suggested during review
retronym Jul 29, 2015
976605e
Simplify and not the source of a test case
retronym Aug 13, 2015
4b85f72
Test case to show completion from Java future before Scala future
retronym Aug 13, 2015
fcdda1a
Remove vague TODO comment.
retronym Aug 13, 2015
385de85
Use `s.c.blocking` in `future.toJava.get`
retronym Aug 13, 2015
1d60cd0
Make toJava(scalaFuture).toCF.obtrude* unsupported
retronym Aug 17, 2015
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19 changes: 16 additions & 3 deletions src/main/scala/scala/concurrent/java8/FutureConvertersImpl.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ package scala.concurrent.java8
// Located in this package to access private[concurrent] members

import scala.concurrent.{ Future, Promise, ExecutionContext, ExecutionContextExecutorService, ExecutionContextExecutor, impl }
import java.util.concurrent.{ CompletionStage, Executor, ExecutorService, CompletableFuture }
import java.util.concurrent._
import scala.util.{ Try, Success, Failure }
import java.util.function.{ BiConsumer, Function ⇒ JF, Consumer, BiFunction }

Expand Down Expand Up @@ -66,8 +66,21 @@ object FuturesConvertersImpl {
cf
}

override def toCompletableFuture(): CompletableFuture[T] =
throw new UnsupportedOperationException("this CompletionStage represents a read-only Scala Future")
/**
* @inheritdoc
*
* WARNING: completing the result of this method will not complete the underlying
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There is no underlying Scala Future or Promise for this class? (CF)

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What happens if the CF is completed by a Scala Future prior to toCompletableFuture.complete(x) gets called?

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There is no underlying Scala Future or Promise for this class? (CF)

The underlying future is the one passed to toJava:

  def toJava[T](f: Future[T]): CompletionStage[T] = {
    val cf = new CF[T]
    implicit val ec = InternalCallbackExecutor
    f onComplete cf
    cf
  }

In my other PR, that also becomes a field of CF so that we can efficiently unwrap it.

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What happens if the CF is completed by a Scala Future prior to toCompletableFuture.complete(x) gets called?

I've added a test case to show what happens, could you please review it?

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That test looks great.

What happens if obtrudeX is called?

* Scala Future or Promise (ie, the one that that was passed to `toJava`.)
*/
override def toCompletableFuture(): CompletableFuture[T] = this

override def obtrudeValue(value: T): Unit = throw new UnsupportedOperationException("obtrudeValue may not be used on the result of toJava(scalaFuture)")

override def obtrudeException(ex: Throwable): Unit = throw new UnsupportedOperationException("obtrudeException may not be used on the result of toJava(scalaFuture)")

override def get(): T = scala.concurrent.blocking(super.get())

override def get(timeout: Long, unit: TimeUnit): T = scala.concurrent.blocking(super.get(timeout, unit))

override def toString: String = super[CompletableFuture].toString
}
Expand Down
88 changes: 84 additions & 4 deletions src/test/java/scala/compat/java8/FutureConvertersTest.java
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Expand Up @@ -7,11 +7,9 @@
import scala.concurrent.Future;
import scala.concurrent.Promise;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.*;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.SECONDS;
import static org.junit.Assert.*;
import static scala.compat.java8.FutureConverters.*;
Expand Down Expand Up @@ -318,4 +316,86 @@ public void testToJavaExceptionally() throws InterruptedException,
latch.countDown();
assertEquals("Hello", second.toCompletableFuture().get());
}

@Test
public void testToJavaThenComposeWithToJavaThenAccept() throws InterruptedException,
ExecutionException, TimeoutException {
// Test case from https://github.com/scala/scala-java8-compat/issues/29
final Promise<String> p1 = promise();
final CompletableFuture<String> future = new CompletableFuture<>();

CompletableFuture.supplyAsync(() -> "Hello").
thenCompose(x -> toJava(p1.future())).handle((x, t) -> future.complete(x));
p1.success("Hello");
assertEquals("Hello", future.get(1000, MILLISECONDS));
}

@Test
public void testToJavaToCompletableFuture() throws ExecutionException, InterruptedException {
final Promise<String> p = promise();
final CompletionStage<String> cs = toJava(p.future());
CompletableFuture<String> cf = cs.toCompletableFuture();
assertEquals("notyet", cf.getNow("notyet"));
p.success("done");
assertEquals("done", cf.get());
}

@Test
public void testToJavaToCompletableFutureDoesNotMutateUnderlyingPromise() throws ExecutionException, InterruptedException {
final Promise<String> p = promise();
Future<String> sf = p.future();
final CompletionStage<String> cs = toJava(sf);
CompletableFuture<String> cf = cs.toCompletableFuture();
assertEquals("notyet", cf.getNow("notyet"));
cf.complete("done");
assertEquals("done", cf.get());
assertFalse(sf.isCompleted());
assertFalse(p.isCompleted());
}

@Test
public void testToJavaToCompletableFutureJavaCompleteCalledAfterScalaComplete() throws ExecutionException, InterruptedException {
final Promise<String> p = promise();
Future<String> sf = p.future();
final CompletionStage<String> cs = toJava(sf);
CompletableFuture<String> cf = cs.toCompletableFuture();
assertEquals("notyet", cf.getNow("notyet"));
p.success("scaladone");
assertEquals("scaladone", cf.get());
cf.complete("javadone");
assertEquals("scaladone", cf.get());
}

@Test
public void testToJavaToCompletableFutureJavaCompleteCalledBeforeScalaComplete() throws ExecutionException, InterruptedException {
final Promise<String> p = promise();
Future<String> sf = p.future();
final CompletionStage<String> cs = toJava(sf);
CompletableFuture<String> cf = cs.toCompletableFuture();
assertEquals("notyet", cf.getNow("notyet"));
cf.complete("javadone");
assertEquals("javadone", cf.get());
p.success("scaladone");
assertEquals("javadone", cf.get());
}

@Test
public void testToJavaToCompletableFutureJavaObtrudeCalledBeforeScalaComplete() throws ExecutionException, InterruptedException {
final Promise<String> p = promise();
Future<String> sf = p.future();
final CompletionStage<String> cs = toJava(sf);
CompletableFuture<String> cf = cs.toCompletableFuture();
try {
cf.obtrudeValue("");
fail();
} catch (UnsupportedOperationException iae) {
// okay
}
try {
cf.obtrudeException(new Exception());
fail();
} catch (UnsupportedOperationException iae) {
// okay
}
}
}