diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/class-wp-widget-factory.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/class-wp-widget-factory.php	Mon Oct 14 17:39:30 2019 +0200
@@ -0,0 +1,144 @@
+<?php
+/**
+ * Widget API: WP_Widget_Factory class
+ *
+ * @package WordPress
+ * @subpackage Widgets
+ * @since 4.4.0
+ */
+
+/**
+ * Singleton that registers and instantiates WP_Widget classes.
+ *
+ * @since 2.8.0
+ * @since 4.4.0 Moved to its own file from wp-includes/widgets.php
+ */
+class WP_Widget_Factory {
+
+	/**
+	 * Widgets array.
+	 *
+	 * @since 2.8.0
+	 * @var array
+	 */
+	public $widgets = array();
+
+	/**
+	 * PHP5 constructor.
+	 *
+	 * @since 4.3.0
+	 */
+	public function __construct() {
+		add_action( 'widgets_init', array( $this, '_register_widgets' ), 100 );
+	}
+
+	/**
+	 * PHP4 constructor.
+	 *
+	 * @since 2.8.0
+	 */
+	public function WP_Widget_Factory() {
+		_deprecated_constructor( 'WP_Widget_Factory', '4.2.0' );
+		self::__construct();
+	}
+
+	/**
+	 * Memory for the number of times unique class instances have been hashed.
+	 *
+	 * This can be eliminated in favor of straight spl_object_hash() when 5.3
+	 * is the minimum requirement for PHP.
+	 *
+	 * @since 4.6.0
+	 * @var array
+	 *
+	 * @see WP_Widget_Factory::hash_object()
+	 */
+	private $hashed_class_counts = array();
+
+	/**
+	 * Hashes an object, doing fallback of `spl_object_hash()` if not available.
+	 *
+	 * This can be eliminated in favor of straight spl_object_hash() when 5.3
+	 * is the minimum requirement for PHP.
+	 *
+	 * @since 4.6.0
+	 *
+	 * @param WP_Widget $widget Widget.
+	 * @return string Object hash.
+	 */
+	private function hash_object( $widget ) {
+		if ( function_exists( 'spl_object_hash' ) ) {
+			return spl_object_hash( $widget );
+		} else {
+			$class_name = get_class( $widget );
+			$hash = $class_name;
+			if ( ! isset( $widget->_wp_widget_factory_hash_id ) ) {
+				if ( ! isset( $this->hashed_class_counts[ $class_name ] ) ) {
+					$this->hashed_class_counts[ $class_name ] = 0;
+				}
+				$this->hashed_class_counts[ $class_name ] += 1;
+				$widget->_wp_widget_factory_hash_id = $this->hashed_class_counts[ $class_name ];
+			}
+			$hash .= ':' . $widget->_wp_widget_factory_hash_id;
+			return $hash;
+		}
+	}
+
+	/**
+	 * Registers a widget subclass.
+	 *
+	 * @since 2.8.0
+	 * @since 4.6.0 Updated the `$widget` parameter to also accept a WP_Widget instance object
+	 *              instead of simply a `WP_Widget` subclass name.
+	 *
+	 * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
+	 */
+	public function register( $widget ) {
+		if ( $widget instanceof WP_Widget ) {
+			$this->widgets[ $this->hash_object( $widget ) ] = $widget;
+		} else {
+			$this->widgets[ $widget ] = new $widget();
+		}
+	}
+
+	/**
+	 * Un-registers a widget subclass.
+	 *
+	 * @since 2.8.0
+	 * @since 4.6.0 Updated the `$widget` parameter to also accept a WP_Widget instance object
+	 *              instead of simply a `WP_Widget` subclass name.
+	 *
+	 * @param string|WP_Widget $widget Either the name of a `WP_Widget` subclass or an instance of a `WP_Widget` subclass.
+	 */
+	public function unregister( $widget ) {
+		if ( $widget instanceof WP_Widget ) {
+			unset( $this->widgets[ $this->hash_object( $widget ) ] );
+		} else {
+			unset( $this->widgets[ $widget ] );
+		}
+	}
+
+	/**
+	 * Serves as a utility method for adding widgets to the registered widgets global.
+	 *
+	 * @since 2.8.0
+	 *
+	 * @global array $wp_registered_widgets
+	 */
+	public function _register_widgets() {
+		global $wp_registered_widgets;
+		$keys = array_keys($this->widgets);
+		$registered = array_keys($wp_registered_widgets);
+		$registered = array_map('_get_widget_id_base', $registered);
+
+		foreach ( $keys as $key ) {
+			// don't register new widget if old widget with the same id is already registered
+			if ( in_array($this->widgets[$key]->id_base, $registered, true) ) {
+				unset($this->widgets[$key]);
+				continue;
+			}
+
+			$this->widgets[$key]->_register();
+		}
+	}
+}