Add missing EventInterface to ease future typehinting using interfaces.

src/Event/Event.php

@@ -14,17 +14,7 @@
  */
 namespace Cake\Event;
 
-/**
- * Represents the transport class of events across the system. It receives a name, subject and an optional
- * payload. The name can be any string that uniquely identifies the event across the application, while the subject
- * represents the object that the event applies to.
- *
- * @property string $name (deprecated) Name of the event
- * @property object $subject (deprecated) The object this event applies to
- * @property mixed $result (deprecated) Property used to retain the result value of the event listeners
- * @property array $data (deprecated) Custom data for the method that receives the event
- */
-class Event
+class Event implements EventInterface
 {
 
     /**

src/Event/EventInterface.php

@@ -0,0 +1,89 @@
+<?php
+/**
+ * CakePHP(tm) : Rapid Development Framework (https://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (https://cakefoundation.org)
+ * @link          https://cakephp.org CakePHP(tm) Project
+ * @since         3.6.0
+ * @license       https://opensource.org/licenses/mit-license.php MIT License
+ */
+namespace Cake\Event;
+
+/**
+ * Represents the transport class of events across the system. It receives a name, subject and an optional
+ * payload. The name can be any string that uniquely identifies the event across the application, while the subject
+ * represents the object that the event applies to.
+ *
+ * @property string $name (deprecated) Name of the event
+ * @property object $subject (deprecated) The object this event applies to
+ * @property mixed $result (deprecated) Property used to retain the result value of the event listeners
+ * @property array $data (deprecated) Custom data for the method that receives the event
+ */
+interface EventInterface
+{
+    /**
+     * Returns the name of this event. This is usually used as the event identifier.
+     *
+     * @return string
+     */
+    public function getName();
+
+    /**
+     * Returns the subject of this event.
+     *
+     * @return object
+     */
+    public function getSubject();
+
+    /**
+     * Stops the event from being used anymore.
+     *
+     * @return void
+     */
+    public function stopPropagation();
+
+    /**
+     * Checks if the event is stopped.
+     *
+     * @return bool True if the event is stopped
+     */
+    public function isStopped();
+
+    /**
+     * The result value of the event listeners.
+     *
+     * @return mixed
+     */
+    public function getResult();
+
+    /**
+     * Listeners can attach a result value to the event.
+     *
+     * @param mixed $value The value to set.
+     * @return $this
+     */
+    public function setResult($value = null);
+
+    /**
+     * Accesses the event data/payload.
+     *
+     * @param string|null $key The data payload element to return, or null to return all data.
+     * @return array|mixed|null The data payload if $key is null, or the data value for the given $key. If the $key does not
+     * exist a null value is returned.
+     */
+    public function getData($key = null);
+
+    /**
+     * Assigns a value to the data/payload of this event.
+     *
+     * @param array|string $key An array will replace all payload data, and a key will set just that array item.
+     * @param mixed $value The value to set.
+     * @return $this
+     */
+    public function setData($key, $value = null);
+}