From: Tim Otten <totten@civicrm.org>
Date: Mon, 15 Aug 2022 23:32:04 +0000 (-0700)
Subject: (REF) Define EventScannerPass (extracted from CRM_Api4_Services)
X-Git-Url: https://vcs.fsf.org/?a=commitdiff_plain;h=c354cc12e344659cf52e2562dae8a9d9237d34f2;p=civicrm-core.git

(REF) Define EventScannerPass (extracted from CRM_Api4_Services)

The `CRM_Api4_Services` implementation has a secret behavior that applies
to all services - it detects the tag 'event_subscriber' and registers with
the dispatcher.

This kind of behavior is often implemented as "compiler pass" and given its
own documentation.
---

diff --git a/CRM/Api4/Services.php b/CRM/Api4/Services.php
index f5581efd0f..34f64e0239 100644
--- a/CRM/Api4/Services.php
+++ b/CRM/Api4/Services.php
@@ -16,7 +16,6 @@
  * @copyright CiviCRM LLC https://civicrm.org/licensing
  */
 
-use Civi\Core\Event\EventScanner;
 use Symfony\Component\DependencyInjection\Reference;
 use Symfony\Component\DependencyInjection\Loader\XmlFileLoader;
 use Symfony\Component\Config\FileLocator;
@@ -38,15 +37,6 @@ class CRM_Api4_Services {
       [new Reference('action_object_provider')]
     );
 
-    // add event subscribers$container->get(
-    $dispatcher = $container->getDefinition('dispatcher');
-    $subscribers = $container->findTaggedServiceIds('event_subscriber');
-
-    foreach (array_keys($subscribers) as $subscriber) {
-      $listenerMap = EventScanner::findListeners($container->findDefinition($subscriber)->getClass());
-      $dispatcher->addMethodCall('addSubscriberServiceMap', [$subscriber, $listenerMap]);
-    }
-
     // add spec providers
     $providers = $container->findTaggedServiceIds('spec_provider');
     $gatherer = $container->getDefinition('spec_gatherer');
diff --git a/Civi/Core/Compiler/EventScannerPass.php b/Civi/Core/Compiler/EventScannerPass.php
new file mode 100644
index 0000000000..9ad002add8
--- /dev/null
+++ b/Civi/Core/Compiler/EventScannerPass.php
@@ -0,0 +1,35 @@
+<?php
+namespace Civi\Core\Compiler;
+
+use Civi\Core\Event\EventScanner;
+use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
+
+/**
+ * Scan for services that have the tag 'event_subscriber'.
+ *
+ * Specifically, any class tagged as `event_subscriber` will be scanned for event listeners.
+ * The subscriber should implement a relevant interface, such as:
+ *
+ * - HookInterface: The class uses `hook_*()` methods.
+ * - EventSubscriberInterface: the class provides a `getSubscribedEvents()` method.
+ *
+ * The list of listeners will be extracted stored as part of the container-cache.
+ *
+ * NOTE: This is similar to Symfony's `RegisterListenersPass()` but differs in a few ways:
+ *   - Works with both HookInterface and EventSubscriberInterface
+ *   - Watches tag 'event_subscriber' (not 'kernel.event_listener' or 'kernel.event_subscriber')
+ */
+class EventScannerPass implements CompilerPassInterface {
+
+  public function process(ContainerBuilder $container) {
+    $dispatcher = $container->getDefinition('dispatcher');
+    $subscribers = $container->findTaggedServiceIds('event_subscriber');
+
+    foreach (array_keys($subscribers) as $subscriber) {
+      $listenerMap = EventScanner::findListeners($container->findDefinition($subscriber)->getClass());
+      $dispatcher->addMethodCall('addSubscriberServiceMap', [$subscriber, $listenerMap]);
+    }
+  }
+
+}
diff --git a/Civi/Core/Container.php b/Civi/Core/Container.php
index d0b70f120e..8cc7d2c0cf 100644
--- a/Civi/Core/Container.php
+++ b/Civi/Core/Container.php
@@ -1,6 +1,7 @@
 <?php
 namespace Civi\Core;
 
+use Civi\Core\Compiler\EventScannerPass;
 use Civi\Core\Event\EventScanner;
 use Civi\Core\Lock\LockManager;
 use Symfony\Component\Config\ConfigCache;
@@ -90,6 +91,7 @@ class Container {
   public function createContainer() {
     $civicrm_base_path = dirname(dirname(__DIR__));
     $container = new ContainerBuilder();
+    $container->addCompilerPass(new EventScannerPass());
     $container->addCompilerPass(new RegisterListenersPass());
     $container->addObjectResource($this);
     $container->setParameter('civicrm_base_path', $civicrm_base_path);