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.

git-svn-id: https://develop.svn.wordpress.org/trunk@45798 602fd350-edb4-49c9-b593-d223f7449a82

src/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.
 	 *

tests/phpunit/tests/widgets.php

@@ -712,6 +712,22 @@ class Tests_Widgets extends WP_UnitTestCase {
 		the_widget( 'Widget_Class' );
 	}
 
+	/**
+	 * @ticket 34226
+	 */
+	public function test_the_widget_should_short_circuit_with_widget_display_callback() {
+		add_filter( 'widget_display_callback', '__return_false' );
+
+		register_widget( 'WP_Widget_Text' );
+
+		ob_start();
+		the_widget( 'WP_Widget_Text' );
+		$widget_content = ob_get_clean();
+		unregister_widget( 'WP_Widget_Text' );
+
+		$this->assertEmpty( $widget_content );
+	}
+
 	/**
 	 * Register nav menu sidebars.
 	 *