V1 gallery - v2 gallery transform

transform-v1-gallery.js

		{
			// Allow transform to new gallery format if experimental flag enabled.
			type: 'block',
			isMultiBlock: false,
			blocks: [ 'core/gallery' ],
			priority: 1,
			isMatch( { ids } ) {
				const settings = select( blockEditorStore ).getSettings();
				return settings.__experimentalGalleryRefactor && ids.length > 0;
			},
			transform( { images, linkTo, sizeSlug } ) {
				let link;
				switch ( linkTo ) {
					case 'post':
						link = LINK_DESTINATION_ATTACHMENT;
						break;
					case 'file':
						link = LINK_DESTINATION_MEDIA;
						break;
					default:
						link = LINK_DESTINATION_NONE;
						break;
				}
				const innerBlocks = images.map( ( image ) =>
					createBlock( 'core/image', {
						id: parseInt( image.id, 10 ),
						url: image.url,
						alt: image.alt,
						caption: image.caption,
						linkDestination: link,
					} )
				);

				return createBlock(
					'core/gallery',
					{ sizeSlug, linkTo: link },
					innerBlocks
				);
			},
		},