Reverts #1824 and instead ddd tryComplete/tryFail methods that allow …

…to complete/fail Future if not yet completed - fixes #1835

src/main/java/io/vertx/core/CompositeFuture.java

@@ -186,17 +186,18 @@ static CompositeFuture join(List<Future> futures) {
   CompositeFuture setHandler(Handler<AsyncResult<CompositeFuture>> handler);
 
   /**
-   * @return false
+   * Set this instance as result. Any handler will be called, if there is one, and the future will be marked as completed.
    */
   @Override
-  boolean complete();
+  void complete();
 
   /**
-   * @return false
+   * Try to set this instance as result. When it happens, any handler will be called, if there is one, and the future will be marked as completed.
+   *
+   * @return false when the future is already completed
    */
   @Override
-  boolean complete(CompositeFuture result);
-
+  boolean tryComplete();
 
   /**
    * Returns a cause of a wrapped future

src/main/java/io/vertx/core/Future.java

@@ -122,35 +122,61 @@ static <T> Future<T> failedFuture(String failureMessage) {
   Future<T> setHandler(Handler<AsyncResult<T>> handler);
 
   /**
-   * Try to set the result. When it happens, any handler will be called, if there is one, and the future will be marked as completed.
+   * Set the result. Any handler will be called, if there is one, and the future will be marked as completed.
+   *
+   * @param result  the result
+   */
+  void complete(T result);
+
+  /**
+   *  Set a null result. Any handler will be called, if there is one, and the future will be marked as completed.
+   */
+  void complete();
+
+  /**
+   * Set the failure. Any handler will be called, if there is one, and the future will be marked as completed.
+   *
+   * @param cause  the failure cause
+   */
+  void fail(Throwable cause);
+
+  /**
+   * Try to set the failure. When it happens, any handler will be called, if there is one, and the future will be marked as completed.
+   *
+   * @param failureMessage  the failure message
+   */
+  void fail(String failureMessage);
+
+  /**
+   * Set the failure. Any handler will be called, if there is one, and the future will be marked as completed.
    *
    * @param result  the result
    * @return false when the future is already completed
    */
-  boolean complete(T result);
+  boolean tryComplete(T result);
 
   /**
    * Try to set the result. When it happens, any handler will be called, if there is one, and the future will be marked as completed.
    *
    * @return false when the future is already completed
    */
-  boolean complete();
+  boolean tryComplete();
 
   /**
    * Try to set the failure. When it happens, any handler will be called, if there is one, and the future will be marked as completed.
    *
    * @param cause  the failure cause
    * @return false when the future is already completed
    */
-  boolean fail(Throwable cause);
+  boolean tryFail(Throwable cause);
 
   /**
    * Try to set the failure. When it happens, any handler will be called, if there is one, and the future will be marked as completed.
    *
    * @param failureMessage  the failure message
    * @return false when the future is already completed
    */
-  boolean fail(String failureMessage);
+  boolean tryFail(String failureMessage);
 
   /**
    * The result of the operation. This will be null if the operation failed.

src/main/java/io/vertx/core/impl/CloseHooks.java

@@ -90,7 +90,7 @@ void run(Handler<AsyncResult<Void>> completionHandler) {
             hook.close(a.completer());
           } catch (Throwable t) {
             log.warn("Failed to run close hooks", t);
-            a.fail(t);
+            a.tryFail(t);
           }
         }
       } else {

src/main/java/io/vertx/core/impl/CompositeFutureImpl.java

@@ -217,17 +217,51 @@ public synchronized CompositeFuture result() {
   }
 
   @Override
-  public boolean complete(CompositeFuture result) {
-    return false;
+  public void complete() {
+    if (!tryComplete()) {
+      throw new IllegalStateException("Result is already complete: " + (this.cause == null ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public void complete(CompositeFuture result) {
+    if (!tryComplete(result)) {
+      throw new IllegalStateException("Result is already complete: " + (this.cause == null ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public void fail(Throwable cause) {
+    if (!tryFail(cause)) {
+      throw new IllegalStateException("Result is already complete: " + (this.cause == null ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public void fail(String failureMessage) {
+    if (!tryFail(failureMessage)) {
+      throw new IllegalStateException("Result is already complete: " + (this.cause == null ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public boolean tryComplete(CompositeFuture result) {
+    Handler<AsyncResult<CompositeFuture>> handler = setCompleted(null);
+    if (handler != null) {
+      handler.handle(this);
+      return true;
+    } else {
+      return false;
+    }
   }
 
   @Override
-  public boolean complete() {
-    return false;
+  public boolean tryComplete() {
+    return tryComplete(this);
   }
 
   @Override
-  public boolean fail(Throwable cause) {
+  public boolean tryFail(Throwable cause) {
     Handler<AsyncResult<CompositeFuture>> handler = setCompleted(cause);
     if (handler != null) {
       handler.handle(this);
@@ -238,8 +272,8 @@ public boolean fail(Throwable cause) {
   }
 
   @Override
-  public boolean fail(String failureMessage) {
-    return fail(new NoStackTraceThrowable(failureMessage));
+  public boolean tryFail(String failureMessage) {
+    return tryFail(new NoStackTraceThrowable(failureMessage));
   }
 
   private Handler<AsyncResult<CompositeFuture>> setCompleted(Throwable cause) {

src/main/java/io/vertx/core/impl/FutureImpl.java

@@ -102,7 +102,35 @@ public Future<T> setHandler(Handler<AsyncResult<T>> handler) {
   }
 
   @Override
-  public boolean complete(T result) {
+  public void complete(T result) {
+    if (!tryComplete(result)) {
+      throw new IllegalStateException("Result is already complete: " + (succeeded ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public void complete() {
+    if (!tryComplete()) {
+      throw new IllegalStateException("Result is already complete: " + (succeeded ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public void fail(Throwable cause) {
+    if (!tryFail(cause)) {
+      throw new IllegalStateException("Result is already complete: " + (succeeded ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public void fail(String failureMessage) {
+    if (!tryFail(failureMessage)) {
+      throw new IllegalStateException("Result is already complete: " + (succeeded ? "succeeded" : "failed"));
+    }
+  }
+
+  @Override
+  public boolean tryComplete(T result) {
     if (succeeded || failed) {
       return false;
     }
@@ -113,8 +141,8 @@ public boolean complete(T result) {
   }
 
   @Override
-  public boolean complete() {
-    return complete(null);
+  public boolean tryComplete() {
+    return tryComplete(null);
   }
 
   public void handle(Future<T> ar) {
@@ -140,7 +168,7 @@ public void handle(AsyncResult<T> asyncResult) {
   }
 
   @Override
-  public boolean fail(Throwable cause) {
+  public boolean tryFail(Throwable cause) {
     if (succeeded || failed) {
       return false;
     }
@@ -151,8 +179,8 @@ public boolean fail(Throwable cause) {
   }
 
   @Override
-  public boolean fail(String failureMessage) {
-    return fail(new NoStackTraceThrowable(failureMessage));
+  public boolean tryFail(String failureMessage) {
+    return tryFail(new NoStackTraceThrowable(failureMessage));
   }
 
   private void checkCallHandler() {