Ticket #46238: 46238a.diff

wp-includes/rest-api/endpoints/class-wp-rest-controller.php

@@ -371 +371 @@
          * Adds the values from additional fields to a data object.
          *
          * @since 4.7.0
+         * @since 5.1.0 includes $skip_field value to return in order to omit the field from the response
          *
          * @param array           $object  Data object.
          * @param WP_REST_Request $request Full details about the request.
@@ -392 +393 @@
                                 continue;
                         }
 
-                        $object[ $field_name ] = call_user_func( $field_options['get_callback'], $object, $field_name, $request, $this->get_object_type() );
+                        /**
+                         * Sentinel value which the callback can return in order
+                         * to indicate that this field should not be added
+                         *
+                         * We're relying on the fact that object identity returns
+                         * whether two objects are the same instance of the same
+                         * class. That means it will be impossible to confuse a
+                         * value created inside the callback with this value.
+                         *
+                         * @example
+                         * function my_get_callback( $object, $field_name, $request, $object_type, $skip_field ) {
+                         *   // only attach video meta to video attachments
+                         *   if ( 0 !== strpos( $object->post_mime_type, 'video/' ) {
+                         *     return $skip_field;
+                         *   }
+                         *
+                         *   return calculate_expensive_metadata( $object->ID );
+                         * }
+                         *
+                         */
+                        $skip_field  = new stdClass;
+                        $field_value = call_user_func( $field_options['get_callback'], $object, $field_name, $request, $this->get_object_type(), $skip_field );
+
+                        if ( $field_value === $skip_field ) {
+                                continue;
+                        }
+
+                        $object[ $field_name ] = $field_value;
                 }
 
                 return $object;