Version 2.0.0 breaks the WooCommerce Integrations tab

In version 2.0.0 a new class file was added and the way in which these are being included was changed to use the autoload_classes() function. However, this function is called via the woocommerce_integrations hook, which is a filter hook expecting an array of integrations to be returned. This is removing the integrations of all other plugins from being loaded into this filter.

Relevant changes:

Index: referralcandy-for-woocommerce/trunk/woocommerce-referralcandy.php
===================================================================
--- a/referralcandy-for-woocommerce/trunk/woocommerce-referralcandy.php
+++ b/referralcandy-for-woocommerce/trunk/woocommerce-referralcandy.php
@@ -7,5 +7,5 @@
  * Author URI: https://www.referralcandy.com
  * Text Domain: woocommerce-referralcandy
- * Version: 1.3.7
+ * Version: 2.0.0
  *
  * This program is free software: you can redistribute it and/or modify
@@ -36,7 +36,6 @@
             public function init() {
                 if (class_exists('WC_Integration')) {
-                    include_once 'includes/class-wc-referralcandy-integration.php';
-
-                    add_filter('woocommerce_integrations', array($this, 'add_integration'));
+                    add_action('woocommerce_integrations', 'autoload_classes');
+                    add_filter('woocommerce_integrations', [$this, 'add_integration']);
                 } else {
                     add_action('admin_notices', 'missing_prerequisite_notification');
@@ -54,4 +53,14 @@
 
         $WC_Referralcandy = new WC_Referralcandy(__FILE__);
+    }
+
+    function autoload_classes() {
+        $files = scandir(dirname(__FILE__) . '/includes');
+        $valid_extensions = ['php'];
+        foreach ($files as $index => $file) {
+            if (in_array(pathinfo($file)['extension'], $valid_extensions)) {
+                require_once('includes/' . pathinfo($file)['basename']);
+            }
+        }
     }

Fix

To fix this you can either roll back to a previous version of the plugin from a backup or patch the plugin manually until fixed by the author in a future version – to patch manually, replace the add_action() call on line 39 with a call to the autoload_classes() function:

public function init() {
    if (class_exists('WC_Integration')) {
        autoload_classes();
        add_filter('woocommerce_integrations', [$this, 'add_integration']);
    } else {
        add_action('admin_notices', 'missing_prerequisite_notification');
    }

    load_plugin_textdomain('woocommerce-referralcandy', false, dirname(plugin_basename(__FILE__)) . '/languages/');
}