Add mixin required for 5.58

mixin/smarty-v2@1.0.0.mixin.php

+<?php
+
+/**
+ * Auto-register "templates/" folder.
+ *
+ * @mixinName smarty-v2
+ * @mixinVersion 1.0.0
+ * @since 5.59
+ *
+ * @param CRM_Extension_MixInfo $mixInfo
+ *   On newer deployments, this will be an instance of MixInfo. On older deployments, Civix may polyfill with a work-a-like.
+ * @param \CRM_Extension_BootCache $bootCache
+ *   On newer deployments, this will be an instance of MixInfo. On older deployments, Civix may polyfill with a work-a-like.
+ */
+return function ($mixInfo, $bootCache) {
+  $dir = $mixInfo->getPath('templates');
+  if (!file_exists($dir)) {
+    return;
+  }
+
+  $register = function() use ($dir) {
+    // This implementation is useful for older versions of CiviCRM. It can be replaced/updated going forward (v1.1+).
+    $smarty = CRM_Core_Smarty::singleton();
+    if (!is_array($smarty->template_dir)) {
+      $this->template_dir = [$smarty->template_dir];
+    }
+    if (!in_array($dir, $smarty->template_dir)) {
+      array_unshift($smarty->template_dir, $dir);
+    }
+  };
+
+  // Let's figure out what environment we're in -- so that we know the best way to call $register().
+
+  if (!empty($GLOBALS['_CIVIX_MIXIN_POLYFILL'])) {
+    // Polyfill Loader (v<=5.45): We're already in the middle of firing `hook_config`.
+    if ($mixInfo->isActive()) {
+      $register();
+    }
+    return;
+  }
+
+  if (CRM_Extension_System::singleton()->getManager()->extensionIsBeingInstalledOrEnabled($mixInfo->longName)) {
+    // New Install, Standard Loader: The extension has just been enabled, and we're now setting it up.
+    // System has already booted. New templates may be needed for upcoming installation steps.
+    $register();
+    return;
+  }
+
+  // Typical Pageview, Standard Loader: Defer the actual registration for a moment -- to ensure that Smarty is online.
+  \Civi::dispatcher()->addListener('hook_civicrm_config', function() use ($mixInfo, $register) {
+    if ($mixInfo->isActive()) {
+      $register();
+    }
+  });
+
+};