Bootstrap wp-admin before rendering widgets – they may rely on wp-adm…

…in functions being loaded. (#33454)

* Bootstrap wp-admin before rendering widgets – they may rely on wp-admin functions being loaded.

* Bootstrap wp-admin function also in /wp/v2/widgets endpoint

* Add a dot at the end of the comment to satisfy linter requirements

* Move the require_once statement to encode_form_data to increase the size of the safety net it provides.

* Update lib/class-wp-rest-widget-types-controller.php

Co-authored-by: Tonya Mork <hello@hellofromtonya.com>

Co-authored-by: Tonya Mork <hello@hellofromtonya.com>

lib/class-wp-rest-widget-types-controller.php

@@ -419,6 +419,9 @@ public function encode_form_data( $request ) {
 			);
 		}
 
+		// Third-party widgets may rely on wp-admin functions. So let's load them before working with the widget object.
+		require_once ABSPATH . 'wp-admin/includes/admin.php';
+
 		// Set the widget's number so that the id attributes in the HTML that we
 		// return are predictable.
 		if ( isset( $request['number'] ) && is_numeric( $request['number'] ) ) {

lib/class-wp-rest-widgets-controller.php

@@ -544,10 +544,16 @@ public function prepare_item_for_response( $item, $request ) {
 			rest_is_field_included( 'rendered', $fields ) &&
 			'wp_inactive_widgets' !== $sidebar_id
 		) {
+			// Some third-party widgets rely on wp-admin functions.
+			require_once ABSPATH . 'wp-admin/includes/admin.php';
+
 			$prepared['rendered'] = trim( wp_render_widget( $widget_id, $sidebar_id ) );
 		}
 
 		if ( rest_is_field_included( 'rendered_form', $fields ) ) {
+			// Some third-party widgets rely on wp-admin functions.
+			require_once ABSPATH . 'wp-admin/includes/admin.php';
+
 			$rendered_form = wp_render_widget_control( $widget_id );
 			if ( ! is_null( $rendered_form ) ) {
 				$prepared['rendered_form'] = trim( $rendered_form );