WIP feat: implement methods completeExceptionallyAsync in `Completa…

…bleFutureUtils` 💣 ✨

TODO add method for cffu and CFExtensions

cffu-core/src/main/java/io/foldright/cffu/CompletableFutureUtils.java

@@ -1710,6 +1710,37 @@ C completeAsync(C cf, Supplier<? extends T> supplier, Executor executor) {
         return cf;
     }
 
+    /**
+     * If not already completed, completes given CompletableFuture with the exception result
+     * of the given Supplier function invoked from an asynchronous task using the default executor.
+     *
+     * @param supplier a function returning the value to be used to complete given CompletableFuture
+     * @return the given CompletableFuture
+     * @see CompletableFuture#completeExceptionally(Throwable)
+     */
+    public static <C extends CompletableFuture<?>>
+    C completeExceptionallyAsync(C cf, Supplier<? extends Throwable> supplier) {
+        return completeExceptionallyAsync(cf, supplier, AsyncPoolHolder.ASYNC_POOL);
+    }
+
+    /**
+     * If not already completed, completes given CompletableFuture with the exception result
+     * of the given Supplier function invoked from an asynchronous task using the given executor.
+     *
+     * @param supplier a function returning the value to be used to complete given CompletableFuture
+     * @param executor the executor to use for asynchronous execution
+     * @return the given CompletableFuture
+     * @see CompletableFuture#completeExceptionally(Throwable)
+     */
+    public static <C extends CompletableFuture<?>>
+    C completeExceptionallyAsync(C cf, Supplier<? extends Throwable> supplier, Executor executor) {
+        requireNonNull(supplier, "supplier is null");
+        requireNonNull(executor, "executor is null");
+        // below code is copied from CompletableFuture#completeAsync with small adoption
+        executor.execute(new CfExCompleterBySupplier(cf, supplier));
+        return cf;
+    }
+
     //# Re-Config methods
 
     /**

cffu-core/src/main/java/io/foldright/cffu/DelayExecutionHelpers.java

@@ -17,7 +17,10 @@
 
 /**
  * Singleton delay scheduler, used only for starting and cancelling tasks
+ * <p>
+ * code is copied from {@link CompletableFuture.Delayer} with small adoption.
  */
+@SuppressWarnings("JavadocReference")
 final class Delayer {
     private static final ScheduledThreadPoolExecutor delayer;
 
@@ -82,7 +85,10 @@ private Delayer() {
 
 /**
  * An executor wrapper with delayed execution.
+ * <p>
+ * code is copied from {@link CompletableFuture.DelayedExecutor} with small adoption.
  */
+@SuppressWarnings("JavadocReference")
 final class DelayedExecutor implements Executor {
     private final long delay;
     private final TimeUnit unit;
@@ -106,8 +112,11 @@ public void execute(@NonNull Runnable r) {
 ////////////////////////////////////////////////////////////////////////////////
 
 /**
- * Action to submit task(Runnable) to executor
+ * Action to submit task(Runnable) to executor.
+ * <p>
+ * code is copied from {@link CompletableFuture.TaskSubmitter} with small adoption.
  */
+@SuppressWarnings("JavadocReference")
 final class TaskSubmitter implements Runnable {
     private final Executor executor;
     private final Runnable action;
@@ -124,8 +133,11 @@ public void run() {
 }
 
 /**
- * Action to cf.completeExceptionally with TimeoutException
+ * Action to cf.completeExceptionally with TimeoutException.
+ * <p>
+ * code is copied from {@link CompletableFuture.Timeout} with small adoption.
  */
+@SuppressWarnings("JavadocReference")
 final class CfTimeout implements Runnable {
     private final CompletableFuture<?> cf;
 
@@ -141,8 +153,11 @@ public void run() {
 }
 
 /**
- * Action to complete cf
+ * Action to complete cf.
+ * <p>
+ * code is copied from {@link CompletableFuture.DelayedCompleter} with small adoption.
  */
+@SuppressWarnings("JavadocReference")
 final class CfCompleter<T> implements Runnable {
     private final CompletableFuture<? super T> cf;
     private final T value;
@@ -159,12 +174,15 @@ public void run() {
 }
 
 /**
- * Action to cancel unneeded scheduled task by Future (for example timeouts)
+ * Action to cancel unneeded scheduled task by Future (for example timeouts).
+ * <p>
+ * code is copied from {@link CompletableFuture.Canceller} with small adoption.
  *
  * @see Delayer#delay(Runnable, long, TimeUnit)
  * @see Delayer#delayToTimoutCf(CompletableFuture, long, TimeUnit)
  * @see Delayer#delayToCompleteCf(CompletableFuture, Object, long, TimeUnit)
  */
+@SuppressWarnings("JavadocReference")
 final class FutureCanceller implements BiConsumer<Object, Throwable> {
     private final Future<?> f;
 
@@ -180,9 +198,8 @@ public void accept(Object ignore, Throwable ex) {
 }
 
 /**
- * code is copied from {@code CompletableFuture#AsyncSupply} with small adoption.
+ * code is copied from {@code CompletableFuture.AsyncSupply} with small adoption.
  */
-@SuppressWarnings("serial")
 @SuppressFBWarnings("SE_BAD_FIELD")
 final class CfCompleterBySupplier<T> extends ForkJoinTask<Void>
         implements Runnable, CompletableFuture.AsynchronousCompletionTask {
@@ -226,3 +243,50 @@ public void run() {
         }
     }
 }
+
+/**
+ * code is adopted from {@code CompletableFuture.AsyncSupply}.
+ */
+@SuppressFBWarnings("SE_BAD_FIELD")
+final class CfExCompleterBySupplier extends ForkJoinTask<Void>
+        implements Runnable, CompletableFuture.AsynchronousCompletionTask {
+    private CompletableFuture<?> dep;
+    private Supplier<? extends Throwable> fn;
+
+    CfExCompleterBySupplier(CompletableFuture<?> dep, Supplier<? extends Throwable> fn) {
+        this.dep = dep;
+        this.fn = fn;
+    }
+
+    @Override
+    public Void getRawResult() {
+        return null;
+    }
+
+    @Override
+    public void setRawResult(Void v) {
+    }
+
+    @Override
+    public boolean exec() {
+        run();
+        return false;
+    }
+
+    @Override
+    public void run() {
+        CompletableFuture<?> d;
+        Supplier<? extends Throwable> f;
+        if ((d = dep) != null && (f = fn) != null) {
+            dep = null;
+            fn = null;
+            if (!d.isDone()) {
+                try {
+                    d.completeExceptionally(f.get());
+                } catch (Throwable ex) {
+                    d.completeExceptionally(ex);
+                }
+            }
+        }
+    }
+}