Gallery block: fix bug with link destination default option not being set (#38310)

Co-authored-by: Glen Davies <glen.davies@a8c.com>

Author: glendaviesnz

packages/block-library/src/gallery/constants.js

@@ -1,3 +1,5 @@
 export const LINK_DESTINATION_NONE = 'none';
 export const LINK_DESTINATION_MEDIA = 'media';
 export const LINK_DESTINATION_ATTACHMENT = 'attachment';
+export const LINK_DESTINATION_MEDIA_WP_CORE = 'file';
+export const LINK_DESTINATION_ATTACHMENT_WP_CORE = 'post';

packages/block-library/src/gallery/utils.js

@@ -5,6 +5,8 @@ import {
 	LINK_DESTINATION_ATTACHMENT,
 	LINK_DESTINATION_MEDIA,
 	LINK_DESTINATION_NONE,
+	LINK_DESTINATION_MEDIA_WP_CORE,
+	LINK_DESTINATION_ATTACHMENT_WP_CORE,
 } from './constants';
 import {
 	LINK_DESTINATION_ATTACHMENT as IMAGE_LINK_DESTINATION_ATTACHMENT,
@@ -21,15 +23,17 @@ import {
  * @return {Object}            New attributes to assign to image block.
  */
 export function getHrefAndDestination( image, destination ) {
-	// Need to determine the URL that the selected destination maps to.
-	// Gutenberg and WordPress use different constants so the new link
-	// destination also needs to be tweaked.
+	// Gutenberg and WordPress use different constants so if image_default_link_type
+	// option is set we need to map from the WP Core values.
+
 	switch ( destination ) {
+		case LINK_DESTINATION_MEDIA_WP_CORE:
 		case LINK_DESTINATION_MEDIA:
 			return {
 				href: image?.source_url || image?.url, // eslint-disable-line camelcase
 				linkDestination: IMAGE_LINK_DESTINATION_MEDIA,
 			};
+		case LINK_DESTINATION_ATTACHMENT_WP_CORE:
 		case LINK_DESTINATION_ATTACHMENT:
 			return {
 				href: image?.link,