first commit

plugins/behaviour/compat/compat.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<extension type="plugin" group="behaviour" method="upgrade">
+	<name>plg_behaviour_compat</name>
+	<author>Joomla! Project</author>
+	<creationDate>2023-09</creationDate>
+	<copyright>(C) 2023 Open Source Matters, Inc.</copyright>
+	<license>GNU General Public License version 2 or later; see LICENSE.txt</license>
+	<authorEmail>admin@joomla.org</authorEmail>
+	<authorUrl>www.joomla.org</authorUrl>
+	<version>4.4.0</version>
+	<description>PLG_COMPAT_XML_DESCRIPTION</description>
+	<namespace path="src">Joomla\Plugin\Behaviour\Compat</namespace>
+	<files>
+		<folder plugin="compat">services</folder>
+		<folder>src</folder>
+	</files>
+	<languages>
+		<language tag="en-GB">language/en-GB/plg_behaviour_compat.ini</language>
+		<language tag="en-GB">language/en-GB/plg_behaviour_compat.sys.ini</language>
+	</languages>
+</extension>

plugins/behaviour/compat/services/provider.php

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+<?php
+
+/**
+ * @package     Joomla.Plugin
+ * @subpackage  Behaviour.compat
+ *
+ * @copyright   (C) 2023 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+defined('_JEXEC') or die;
+
+use Joomla\CMS\Extension\PluginInterface;
+use Joomla\CMS\Factory;
+use Joomla\CMS\Plugin\PluginHelper;
+use Joomla\DI\Container;
+use Joomla\DI\ServiceProviderInterface;
+use Joomla\Event\DispatcherInterface;
+use Joomla\Plugin\Behaviour\Compat\Extension\Compat;
+
+return new class () implements ServiceProviderInterface {
+    /**
+     * Registers the service provider with a DI container.
+     *
+     * @param   Container  $container  The DI container.
+     *
+     * @return  void
+     * @since   4.4.0
+     */
+    public function register(Container $container)
+    {
+        $container->set(
+            PluginInterface::class,
+            function (Container $container) {
+                $plugin     = PluginHelper::getPlugin('behaviour', 'compat');
+                $dispatcher = $container->get(DispatcherInterface::class);
+
+                $plugin = new Compat($dispatcher, (array) $plugin);
+                $plugin->setApplication(Factory::getApplication());
+
+                return $plugin;
+            }
+        );
+    }
+};

plugins/behaviour/compat/src/Extension/Compat.php

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+<?php
+
+/**
+ * @package     Joomla.Plugin
+ * @subpackage  Behaviour.compat
+ *
+ * @copyright   (C) 2023 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Plugin\Behaviour\Compat\Extension;
+
+use Joomla\CMS\Plugin\CMSPlugin;
+use Joomla\Event\SubscriberInterface;
+
+// phpcs:disable PSR1.Files.SideEffects
+\defined('_JEXEC') or die;
+// phpcs:enable PSR1.Files.SideEffects
+
+/**
+ * Joomla! Compat Plugin.
+ *
+ * @since  4.4.0
+ */
+final class Compat extends CMSPlugin implements SubscriberInterface
+{
+    /**
+     * Returns an array of CMS events this plugin will listen to and the respective handlers.
+     *
+     * @return  array
+     *
+     * @since  4.4.0
+     */
+    public static function getSubscribedEvents(): array
+    {
+        /**
+         * This plugin does not listen to any events.
+         */
+        return [];
+    }
+}