Widgets: Allow for short-circuiting widget output in `the_widget()` using the `widget_display_callback` filter, for consistency with output via a registered sidebar.

Props MarcGuay, donmhico.
Fixes #34226.
Built from https://develop.svn.wordpress.org/trunk@45798


git-svn-id: http://core.svn.wordpress.org/trunk@45609 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-alpha-45797';
+$wp_version = '5.3-alpha-45798';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

wp-includes/widgets.php

@@ -1125,6 +1125,13 @@ function the_widget( $widget, $instance = array(), $args = array() ) {
 
 	$instance = wp_parse_args( $instance );
 
+	/** This filter is documented in wp-includes/class-wp-widget.php */
+	$instance = apply_filters( 'widget_display_callback', $instance, $widget_obj, $args );
+
+	if ( false === $instance ) {
+		return;
+	}
+
 	/**
 	 * Fires before rendering the requested widget.
 	 *