From b4e1d12ec64332fd128c876e62510d87d36d5e84 Mon Sep 17 00:00:00 2001
From: Tim Otten <totten@civicrm.org>
Date: Mon, 15 Aug 2022 21:53:34 -0700
Subject: [PATCH] CiviEventDispatcher - Fix pass-by-reference of hook-style
 arguments for service-based listeners

Suppose you are firing `hook_civicrm_foo` to a serivce-based listener
taht uses hook-style arguments. Conceptually, this is a call like:

Civi::service('foo')->hook_civicrm_foo($arg1, &$arg2, $arg3);

Before this patch, all values are pass-by-value. Changes to `&$arg2`
are not propagated back out.

The patch ensures that `&$arg2` propagates back out.
---
 Civi/Core/CiviEventDispatcher.php            | 10 +++++-
 Civi/Core/Event/HookStyleServiceListener.php | 37 ++++++++++++++++++++
 Civi/Core/Event/ServiceListener.php          | 13 ++++---
 3 files changed, 55 insertions(+), 5 deletions(-)
 create mode 100644 Civi/Core/Event/HookStyleServiceListener.php

diff --git a/Civi/Core/CiviEventDispatcher.php b/Civi/Core/CiviEventDispatcher.php
index d8db0119bc..3aec51f3d1 100644
--- a/Civi/Core/CiviEventDispatcher.php
+++ b/Civi/Core/CiviEventDispatcher.php
@@ -155,7 +155,15 @@ class CiviEventDispatcher extends EventDispatcher {
       throw new \InvalidArgumentException('Expected an array("service", "method") argument');
     }
 
-    $this->addListener($eventName, new \Civi\Core\Event\ServiceListener($callback), $priority);
+    if ($eventName[0] === '&') {
+      $eventName = substr($eventName, 1);
+      $listener = new \Civi\Core\Event\HookStyleServiceListener($callback);
+    }
+    else {
+      $listener = new \Civi\Core\Event\ServiceListener($callback);
+    }
+
+    $this->addListener($eventName, $listener, $priority);
   }
 
   /**
diff --git a/Civi/Core/Event/HookStyleServiceListener.php b/Civi/Core/Event/HookStyleServiceListener.php
new file mode 100644
index 0000000000..53a03c40b7
--- /dev/null
+++ b/Civi/Core/Event/HookStyleServiceListener.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Civi\Core\Event;
+
+/**
+ * A hook-style service-listener is a callable with two properties:
+ *
+ * - The parameters are given in hook style.
+ * - The callback is a method in a service-class.
+ *
+ * It is comparable to running:
+ *
+ *   Civi::service('foo')->hook_civicrm_foo($arg1, $arg2, ...);
+ */
+class HookStyleServiceListener extends ServiceListener {
+
+  public function __invoke(...$args) {
+    if ($this->liveCb === NULL) {
+      $c = $this->container ?: \Civi::container();
+      $this->liveCb = [$c->get($this->inertCb[0]), $this->inertCb[1]];
+    }
+
+    $result = call_user_func_array($this->liveCb, $args[0]->getHookValues());
+    $args[0]->addReturnValues($result);
+  }
+
+  public function __toString() {
+    $class = $this->getServiceClass();
+    if ($class) {
+      return sprintf('$(%s)->%s(...$args) [%s]', $this->inertCb[0], $this->inertCb[1], $class);
+    }
+    else {
+      return sprintf('\$(%s)->%s(...$args)', $this->inertCb[0], $this->inertCb[1]);
+    }
+  }
+
+}
diff --git a/Civi/Core/Event/ServiceListener.php b/Civi/Core/Event/ServiceListener.php
index 63df85bc71..faf58cc7fd 100644
--- a/Civi/Core/Event/ServiceListener.php
+++ b/Civi/Core/Event/ServiceListener.php
@@ -24,18 +24,18 @@ class ServiceListener {
    * @var array
    *   Ex: ['service_name', 'someMethod']
    */
-  private $inertCb = NULL;
+  protected $inertCb = NULL;
 
   /**
    * @var array|null
    *   Ex: [$svcObj, 'someMethod']
    */
-  private $liveCb = NULL;
+  protected $liveCb = NULL;
 
   /**
    * @var \Symfony\Component\DependencyInjection\ContainerInterface
    */
-  private $container = NULL;
+  protected $container = NULL;
 
   /**
    * @param array $callback
@@ -53,7 +53,7 @@ class ServiceListener {
     return call_user_func_array($this->liveCb, $args);
   }
 
-  public function __toString() {
+  protected function getServiceClass(): ?string {
     $class = NULL;
     if (\Civi\Core\Container::isContainerBooted()) {
       try {
@@ -63,6 +63,11 @@ class ServiceListener {
       catch (Throwable $t) {
       }
     }
+    return $class;
+  }
+
+  public function __toString() {
+    $class = $this->getServiceClass();
     if ($class) {
       return sprintf('$(%s)->%s($e) [%s]', $this->inertCb[0], $this->inertCb[1], $class);
     }
-- 
2.25.1