Inject theme attr in patterns controller

src/wp-includes/rest-api/endpoints/class-wp-rest-block-patterns-controller.php

@@ -115,6 +115,7 @@ public function get_items( $request ) {
 		$patterns = WP_Block_Patterns_Registry::get_instance()->get_all_registered();
 		foreach ( $patterns as $pattern ) {
 			$migrated_pattern = $this->migrate_pattern_categories( $pattern );
+			$prepared_pattern = $this->prepare_pattern_content( $pattern );
 			$prepared_pattern = $this->prepare_item_for_response( $migrated_pattern, $request );
 			$response[]       = $this->prepare_response_for_collection( $prepared_pattern );
 		}
@@ -151,6 +152,11 @@ protected function migrate_pattern_categories( $pattern ) {
 		return $pattern;
 	}
 
+	protected function prepare_pattern_content( $pattern ) {
+		$blocks             = parse_blocks( $pattern['content'] );
+		$pattern['content'] = traverse_and_serialize_blocks( $blocks, '_inject_theme_attribute_in_template_part_block' );
+	}
+
 	/**
 	 * Prepare a raw block pattern before it gets output in a REST API response.
 	 *