Ticket #54917: 54917.2.diff

src/wp-includes/block-template.php

@@ -46 +46 @@
  * @return string The path to the Full Site Editing template canvas file, or the fallback PHP template.
  */
 function locate_block_template( $template, $type, array $templates ) {
+        if ( ! current_theme_supports( 'block-templates' ) ) {
+                return $template;
+        }
+
         global $_wp_current_template_content;
 
         if ( $template ) {

tests/phpunit/tests/block-template.php

@@ -18 +18 @@
         public function set_up() {
                 parent::set_up();
                 switch_theme( 'block-theme' );
+                do_action( 'setup_theme' );
         }
 
         public function tear_down() {