Ticket #40907: custom-html-widget-shortcode-support.diff

src/wp-includes/widgets/class-wp-widget-custom-html.php

@@ -63 +63 @@
 
                 $content = $instance['content'];
 
+                // Just-in-time add shortcode handling if a plugin added it for the Text widget.
+                $add_text_widget_shortcode_handling = (
+                        false !== has_filter( 'widget_text', 'do_shortcode' )
+                        &&
+                        false === has_filter( 'widget_custom_html_content', 'do_shortcode' )
+                );
+                if ( $add_text_widget_shortcode_handling ) {
+                        add_filter( 'widget_custom_html_content', 'do_shortcode', 10, 2 );
+                }
+
                 /**
                  * Filters the content of the Custom HTML widget.
                  *
@@ -74 +84 @@
                  */
                 $content = apply_filters( 'widget_custom_html_content', $content, $instance, $this );
 
+                if ( $add_text_widget_shortcode_handling ) {
+                        remove_filter( 'widget_custom_html_content', 'do_shortcode' );
+                }
+
                 echo $args['before_widget'];
                 if ( ! empty( $title ) ) {
                         echo $args['before_title'] . $title . $args['after_title'];