[6.1] [RFC] CMSPlugin: Subscriber Registration Checker Interface

libraries/src/Event/SubscriberRegistrationCheckerInterface.php

@@ -0,0 +1,31 @@
+<?php
+
+/**
+ * Joomla! Content Management System
+ *
+ * @copyright  (C) 2024 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license    GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\CMS\Event;
+
+// phpcs:disable PSR1.Files.SideEffects
+\defined('_JEXEC') or die;
+// phpcs:enable PSR1.Files.SideEffects
+
+/**
+ * Provides a method to check whether the Subscriber (or event listener) should be registered.
+ *
+ * @since  __DEPLOY_VERSION__
+ */
+interface SubscriberRegistrationCheckerInterface
+{
+    /**
+     * Check whether the Subscriber (or event listener) should be registered.
+     *
+     * @return bool
+     *
+     * @since  __DEPLOY_VERSION__
+     */
+    public function shouldRegisterListeners(): bool;
+}

libraries/src/Plugin/PluginHelper.php

@@ -10,6 +10,7 @@
 namespace Joomla\CMS\Plugin;
 
 use Joomla\CMS\Cache\Exception\CacheExceptionInterface;
+use Joomla\CMS\Event\SubscriberRegistrationCheckerInterface;
 use Joomla\CMS\Factory;
 use Joomla\Event\DispatcherAwareInterface;
 use Joomla\Event\DispatcherInterface;
@@ -239,6 +240,11 @@ protected static function import($plugin, $autocreate = true, ?DispatcherInterfa
             return;
         }
 
+        // Check whether we should register the subscriber in current runtime
+        if ($plugin instanceof SubscriberRegistrationCheckerInterface && !$plugin->shouldRegisterListeners()) {
+            return;
+        }
+
         // @TODO: Starting from 7.0 it should use $dispatcher->addSubscriber($plugin); for plugins which implement SubscriberInterface.
         $plugin->registerListeners();
     }

plugins/system/debug/src/Extension/Debug.php

@@ -21,6 +21,7 @@
 use Joomla\CMS\Event\Application\BeforeCompileHeadEvent;
 use Joomla\CMS\Event\Application\BeforeRespondEvent;
 use Joomla\CMS\Event\Plugin\AjaxEvent;
+use Joomla\CMS\Event\SubscriberRegistrationCheckerInterface;
 use Joomla\CMS\Log\Log;
 use Joomla\CMS\Log\LogEntry;
 use Joomla\CMS\Log\Logger\InMemoryLogger;
@@ -56,7 +57,7 @@
  *
  * @since  1.5
  */
-final class Debug extends CMSPlugin implements SubscriberInterface
+final class Debug extends CMSPlugin implements SubscriberInterface, SubscriberRegistrationCheckerInterface
 {
     use DatabaseAwareTrait;
 
@@ -227,6 +228,20 @@ public function __construct(array $config, CMSApplicationInterface $app, Databas
         }
     }
 
+    /**
+     * Check whether the Subscriber should be registered.
+     *
+     * @return bool
+     *
+     * @since  __DEPLOY_VERSION__
+     */
+    public function shouldRegisterListeners(): bool
+    {
+        $app = $this->getApplication();
+
+        return $app->get('debug') || $app->get('debug_lang');
+    }
+
     /**
      * Add an assets for debugger.
      *

plugins/system/guidedtours/services/provider.php

@@ -38,7 +38,6 @@ function (Container $container) {
 
                 $plugin = new GuidedTours(
                     (array) PluginHelper::getPlugin('system', 'guidedtours'),
-                    $app->isClient('administrator')
                 );
 
                 $plugin->setApplication($app);

plugins/system/guidedtours/src/Extension/GuidedTours.php

@@ -12,6 +12,7 @@
 
 use Joomla\CMS\Component\ComponentHelper;
 use Joomla\CMS\Date\Date;
+use Joomla\CMS\Event\SubscriberRegistrationCheckerInterface;
 use Joomla\CMS\Language\Multilanguage;
 use Joomla\CMS\Language\Text;
 use Joomla\CMS\Plugin\CMSPlugin;
@@ -32,7 +33,7 @@
  *
  * @since  4.3.0
  */
-final class GuidedTours extends CMSPlugin implements SubscriberInterface
+final class GuidedTours extends CMSPlugin implements SubscriberInterface, SubscriberRegistrationCheckerInterface
 {
     use DatabaseAwareTrait;
 
@@ -64,42 +65,30 @@ final class GuidedTours extends CMSPlugin implements SubscriberInterface
     ];
 
     /**
-     * An internal flag whether plugin should listen any event.
-     *
-     * @var bool
-     *
-     * @since   4.3.0
-     */
-    protected static $enabled = false;
-
-    /**
-     * Constructor
+     * function for getSubscribedEvents : new Joomla 4 feature
      *
-     * @param   array                $config      An optional associative array of configuration settings.
-     * @param   boolean              $enabled     An internal flag whether plugin should listen any event.
+     * @return array
      *
      * @since   4.3.0
      */
-    public function __construct(array $config = [], bool $enabled = false)
+    public static function getSubscribedEvents(): array
     {
-        self::$enabled = $enabled;
-
-        parent::__construct($config);
+        return [
+            'onAjaxGuidedtours'   => 'startTour',
+            'onBeforeCompileHead' => 'onBeforeCompileHead',
+        ];
     }
 
     /**
-     * function for getSubscribedEvents : new Joomla 4 feature
+     * Check whether the Subscriber should be registered.
      *
-     * @return array
+     * @return bool
      *
-     * @since   4.3.0
+     * @since  __DEPLOY_VERSION__
      */
-    public static function getSubscribedEvents(): array
+    public function shouldRegisterListeners(): bool
     {
-        return self::$enabled ? [
-            'onAjaxGuidedtours'   => 'startTour',
-            'onBeforeCompileHead' => 'onBeforeCompileHead',
-        ] : [];
+        return $this->getApplication()->isClient('administrator');
     }
 
     /**