wp-includes/class-wp-customize-widgets.php:1554Strips out widget IDs for widgets which are no longer registered.
$widget_idsarrayarray public function sanitize_sidebar_widgets_js_instance( $widget_ids ) { global $wp_registered_widgets; $widget_ids = array_values( array_intersect( $widget_ids, array_keys( $wp_registered_widgets ) ) ); return $widget_ids; }Introduced in 3.9.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-customize-widgets.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.