Added CancelTaskException (#4186)

src/scheduler/CancelTaskException.php

@@ -0,0 +1,32 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\scheduler;
+
+/**
+ * This exception can be thrown from Task::onRun() to cancel the execution of the task.
+ * @see Task::onRun()
+ */
+final class CancelTaskException extends \Exception{
+
+}

src/scheduler/Task.php

@@ -49,6 +49,8 @@ abstract class Task{
 
 	/**
 	 * Actions to execute when run
+	 *
+	 * @throws CancelTaskException
 	 */
 	abstract public function onRun() : void;
 

src/scheduler/TaskHandler.php

@@ -115,6 +115,8 @@ class TaskHandler{
 		$this->timings->startTiming();
 		try{
 			$this->task->onRun();
+		}catch(CancelTaskException $e){
+			$this->cancel();
 		}finally{
 			$this->timings->stopTiming();
 		}