FULL PRODUCT VERSION :
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux  3.13.0-37-generic #64-Ubuntu SMP Mon Sep 22 21:28:38 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
CompletableFuture.thenCompose inconsistently handles exception thrown from the CompletionStage created by function. See the steps to reproduce 

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
I have this two tests that only differ in order of execution but produce different output.

@Test
public void completedAfter() {
    CompletableFuture<String> future1 = new CompletableFuture<>();
    CompletableFuture<String> future2 = new CompletableFuture<>();

    future1.thenCompose(x -> future2).whenComplete((r, e) -> System.out.println("After: " + e));

    future1.complete("value");
    future2.completeExceptionally(new RuntimeException());
}

@Test
public void completedBefore() {
    CompletableFuture<String> future1 = new CompletableFuture<>();
    CompletableFuture<String> future2 = new CompletableFuture<>();

    future1.complete("value");
    future2.completeExceptionally(new RuntimeException());

    future1.thenCompose(x -> future2).whenComplete((r, e) -> System.out.println("Before: " +e));
}

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Consistent output, most likely:

After: java.util.concurrent.CompletionException: java.lang.RuntimeException
Before: java.util.concurrent.CompletionException: java.lang.RuntimeException

ACTUAL -
Inconsistent output:

After: java.util.concurrent.CompletionException: java.lang.RuntimeException
Before: java.lang.RuntimeException


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import org.junit.Test;

import java.util.concurrent.CompletableFuture;

public class CompletableFutureComposeTest {

    @Test
    public void completedAfter() {
        CompletableFuture<String> future1 = new CompletableFuture<>();
        CompletableFuture<String> future2 = new CompletableFuture<>();

        future1.thenCompose(x -> future2).whenComplete((r, e) -> System.out.println("After: " + e));

        future1.complete("value");
        future2.completeExceptionally(new RuntimeException());
    }

    @Test
    public void completedBefore() {
        CompletableFuture<String> future1 = new CompletableFuture<>();
        CompletableFuture<String> future2 = new CompletableFuture<>();

        future1.complete("value");
        future2.completeExceptionally(new RuntimeException());

        future1.thenCompose(x -> future2).whenComplete((r, e) -> System.out.println("Before: " +e));
    }
}
---------- END SOURCE ----------