--- jsr166/src/test/tck/CompletableFutureTest.java	2015/09/06 22:21:07	1.122
+++ jsr166/src/test/tck/CompletableFutureTest.java	2015/11/15 00:37:50	1.128
@@ -7,10 +7,20 @@
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
+import static java.util.concurrent.CompletableFuture.completedFuture;
+import static java.util.concurrent.CompletableFuture.failedFuture;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
+import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.CancellationException;
 import java.util.concurrent.CompletableFuture;
@@ -28,8 +38,10 @@ import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;
 import java.util.function.Function;
+import java.util.function.Predicate;
 import java.util.function.Supplier;
 
+import junit.framework.AssertionFailedError;
 import junit.framework.Test;
 import junit.framework.TestSuite;
 
@@ -828,9 +840,9 @@ public class CompletableFutureTest exten
         if (!createIncomplete) assertTrue(f.complete(v1));
         final CompletableFuture<Integer> g = f.exceptionally
             ((Throwable t) -> {
-                // Should not be called
                 a.getAndIncrement();
-                throw new AssertionError();
+                threadFail("should not be called");
+                return null;            // unreached
             });
         if (createIncomplete) assertTrue(f.complete(v1));
 
@@ -889,7 +901,7 @@ public class CompletableFutureTest exten
      * whenComplete action executes on normal completion, propagating
      * source result.
      */
-    public void testWhenComplete_normalCompletion1() {
+    public void testWhenComplete_normalCompletion() {
         for (ExecutionMode m : ExecutionMode.values())
         for (boolean createIncomplete : new boolean[] { true, false })
         for (Integer v1 : new Integer[] { 1, null })
@@ -3688,4 +3700,226 @@ public class CompletableFutureTest exten
         }
     }}
 
+    /**
+     * Minimal completion stages throw UOE for all non-CompletionStage methods
+     */
+    public void testMinimalCompletionStage_minimality() {
+        if (!testImplementationDetails) return;
+        Function<Method, String> toSignature =
+            (method) -> method.getName() + Arrays.toString(method.getParameterTypes());
+        Predicate<Method> isNotStatic =
+            (method) -> (method.getModifiers() & Modifier.STATIC) == 0;
+        List<Method> minimalMethods =
+            Stream.of(Object.class, CompletionStage.class)
+            .flatMap((klazz) -> Stream.of(klazz.getMethods()))
+            .filter(isNotStatic)
+            .collect(Collectors.toList());
+        // Methods from CompletableFuture permitted NOT to throw UOE
+        String[] signatureWhitelist = {
+            "newIncompleteFuture[]",
+            "defaultExecutor[]",
+            "minimalCompletionStage[]",
+            "copy[]",
+        };
+        Set<String> permittedMethodSignatures =
+            Stream.concat(minimalMethods.stream().map(toSignature),
+                          Stream.of(signatureWhitelist))
+            .collect(Collectors.toSet());
+        List<Method> allMethods = Stream.of(CompletableFuture.class.getMethods())
+            .filter(isNotStatic)
+            .filter((method) -> !permittedMethodSignatures.contains(toSignature.apply(method)))
+            .collect(Collectors.toList());
+
+        CompletionStage<Integer> minimalStage =
+            new CompletableFuture<Integer>().minimalCompletionStage();
+
+        List<Method> bugs = new ArrayList<>();
+        for (Method method : allMethods) {
+            Class<?>[] parameterTypes = method.getParameterTypes();
+            Object[] args = new Object[parameterTypes.length];
+            // Manufacture boxed primitives for primitive params
+            for (int i = 0; i < args.length; i++) {
+                Class<?> type = parameterTypes[i];
+                if (parameterTypes[i] == boolean.class)
+                    args[i] = false;
+                else if (parameterTypes[i] == int.class)
+                    args[i] = 0;
+                else if (parameterTypes[i] == long.class)
+                    args[i] = 0L;
+            }
+            try {
+                method.invoke(minimalStage, args);
+                bugs.add(method);
+            }
+            catch (java.lang.reflect.InvocationTargetException expected) {
+                if (! (expected.getCause() instanceof UnsupportedOperationException)) {
+                    bugs.add(method);
+                    // expected.getCause().printStackTrace();
+                }
+            }
+            catch (ReflectiveOperationException bad) { throw new Error(bad); }
+        }
+        if (!bugs.isEmpty())
+            throw new Error("Methods did not throw UOE: " + bugs.toString());
+    }
+
+    static class Monad {
+        static class MonadError extends Error {
+            public MonadError() { super("monadic zero"); }
+        }
+        // "return", "unit"
+        static <T> CompletableFuture<T> unit(T value) {
+            return completedFuture(value);
+        }
+        // monadic zero ?
+        static <T> CompletableFuture<T> zero(T value) {
+            return failedFuture(new MonadError());
+        }
+        // >=>
+        static <T,U,V> Function<T, CompletableFuture<V>> compose
+            (Function<T, CompletableFuture<U>> f,
+             Function<U, CompletableFuture<V>> g) {
+            return (x) -> f.apply(x).thenCompose(g);
+        }
+
+        static void assertZero(CompletableFuture<?> f) {
+            try {
+                f.getNow(null);
+                throw new AssertionFailedError("should throw");
+            } catch (CompletionException success) {
+                assertTrue(success.getCause() instanceof MonadError);
+            }
+        }
+
+        static <T> void assertFutureEquals(CompletableFuture<T> f,
+                                           CompletableFuture<T> g) {
+            T fval = null, gval = null;
+            Throwable fex = null, gex = null;
+
+            try { fval = f.get(); }
+            catch (ExecutionException ex) { fex = ex.getCause(); }
+            catch (Throwable ex) { fex = ex; }
+
+            try { gval = g.get(); }
+            catch (ExecutionException ex) { gex = ex.getCause(); }
+            catch (Throwable ex) { gex = ex; }
+
+            if (fex != null || gex != null)
+                assertSame(fex.getClass(), gex.getClass());
+            else
+                assertEquals(fval, gval);
+        }
+
+        static class PlusFuture<T> extends CompletableFuture<T> {
+            AtomicReference<Throwable> firstFailure = new AtomicReference<>(null);
+        }
+
+        // Monadic "plus"
+        static <T> CompletableFuture<T> plus(CompletableFuture<? extends T> f,
+                                             CompletableFuture<? extends T> g) {
+            PlusFuture<T> plus = new PlusFuture<T>();
+            BiConsumer<T, Throwable> action = (T result, Throwable fail) -> {
+                if (result != null) {
+                    if (plus.complete(result))
+                        if (plus.firstFailure.get() != null)
+                            plus.firstFailure.set(null);
+                }
+                else if (plus.firstFailure.compareAndSet(null, fail)) {
+                    if (plus.isDone())
+                        plus.firstFailure.set(null);
+                } else {
+                    if (plus.completeExceptionally(fail))
+                        plus.firstFailure.set(null);
+                }
+            };
+            f.whenComplete(action);
+            g.whenComplete(action);
+            return plus;
+        }
+    }
+
+    /**
+     * CompletableFuture is an additive monad - sort of.
+     * https://en.wikipedia.org/wiki/Monad_(functional_programming)#Additive_monads
+     */
+    public void testAdditiveMonad() throws Throwable {
+        // Some mutually non-commutative functions
+        Function<Long, CompletableFuture<Long>> triple
+            = (x) -> completedFuture(3 * x);
+        Function<Long, CompletableFuture<Long>> inc
+            = (x) -> completedFuture(x + 1);
+
+        Function<Long, CompletableFuture<Long>> unit = Monad::unit;
+        Function<Long, CompletableFuture<Long>> zero = Monad::zero;
+
+        // unit is a right identity: m >>= unit === m
+        Monad.assertFutureEquals(
+            inc.apply(5L).thenCompose(unit),
+            inc.apply(5L));
+        // unit is a left identity: (unit x) >>= f === f x
+        Monad.assertFutureEquals(
+            unit.apply(5L).thenCompose(inc),
+            inc.apply(5L));
+        // associativity: (m >>= f) >>= g === m >>= ( \x -> (f x >>= g) )
+        Monad.assertFutureEquals(
+            unit.apply(5L).thenCompose(inc).thenCompose(triple),
+            unit.apply(5L).thenCompose((x) -> inc.apply(x).thenCompose(triple)));
+
+        // zero is a monadic zero
+        Monad.assertZero(zero.apply(5L));
+        // left zero: zero >>= f === zero
+        Monad.assertZero(zero.apply(5L).thenCompose(inc));
+        // right zero: f >>= zero === zero
+        Monad.assertZero(inc.apply(5L).thenCompose(zero));
+
+        // inc plus zero === inc
+        Monad.assertFutureEquals(
+            inc.apply(5L),
+            Monad.plus(inc.apply(5L), zero.apply(5L)));
+        // zero plus inc === inc
+        Monad.assertFutureEquals(
+            inc.apply(5L),
+            Monad.plus(zero.apply(5L), inc.apply(5L)));
+        // zero plus zero === zero
+        Monad.assertZero(Monad.plus(zero.apply(5L), zero.apply(5L)));
+        {
+            CompletableFuture<Long> f = Monad.plus(inc.apply(5L), inc.apply(8L));
+            assertTrue(f.get() == 6L || f.get() == 9L);
+        }
+
+        CompletableFuture<Long> godot = new CompletableFuture<>();
+        // inc plus godot === inc (doesn't wait for godot)
+        Monad.assertFutureEquals(
+            inc.apply(5L),
+            Monad.plus(inc.apply(5L), godot));
+        // godot plus inc === inc (doesn't wait for godot)
+        Monad.assertFutureEquals(
+            inc.apply(5L),
+            Monad.plus(godot, inc.apply(5L)));
+    }
+
+//     static <U> U join(CompletionStage<U> stage) {
+//         CompletableFuture<U> f = new CompletableFuture<>();
+//         stage.whenComplete((v, ex) -> {
+//             if (ex != null) f.completeExceptionally(ex); else f.complete(v);
+//         });
+//         return f.join();
+//     }
+
+//     static <U> boolean isDone(CompletionStage<U> stage) {
+//         CompletableFuture<U> f = new CompletableFuture<>();
+//         stage.whenComplete((v, ex) -> {
+//             if (ex != null) f.completeExceptionally(ex); else f.complete(v);
+//         });
+//         return f.isDone();
+//     }
+
+//     static <U> U join2(CompletionStage<U> stage) {
+//         return stage.toCompletableFuture().copy().join();
+//     }
+
+//     static <U> boolean isDone2(CompletionStage<U> stage) {
+//         return stage.toCompletableFuture().copy().isDone();
+//     }
+
 }