Adding a server render_callback in order to add a data-id attribute t…

…o the image element.

Check for existing data-id attribute on the image block content
Wrapping $attributes['id'] in an isset check to catch undefined indexes

lib/blocks.php

@@ -66,6 +66,8 @@ function gutenberg_reregister_core_block_types() {
 				'comment-template.php'          => 'core/comment-template',
 				'file.php'                      => 'core/file',
 				'home-link.php'                 => 'core/home-link',
+				'image.php'                     => 'core/image',
+				'gallery.php'                   => 'core/gallery',
 				'latest-comments.php'           => 'core/latest-comments',
 				'latest-posts.php'              => 'core/latest-posts',
 				'loginout.php'                  => 'core/loginout',

packages/block-library/src/image/index.php

@@ -0,0 +1,40 @@
+<?php
+/**
+ * Server-side rendering of the `core/image` block.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Renders the `core/image` block on the server.
+ *
+ * @param  array $attributes The block attributes.
+ * @param  array $content    The block content.
+ * @return string            Returns the block content with the data-id attribute added.
+ */
+function render_block_core_image( $attributes, $content ) {
+	if ( isset( $attributes['id'] ) ) {
+		// Add the data-id="$id" attribute to the img element
+		// to provide backwards compatibility for the Gallery Block,
+		// which now wraps Image Blocks within innerBlocks.
+		$data_id_attribute = 'data-id="' . esc_attr( $attributes['id'] ) . '"';
+		if ( ! strpos( $content, $data_id_attribute ) ) {
+			$content = str_replace( '<img', '<img ' . $data_id_attribute . ' ', $content );
+		}
+	}
+	return $content;
+}
+
+
+/**
+ * Register image block.
+ */
+function register_block_core_image() {
+	register_block_type_from_metadata(
+		__DIR__ . '/image',
+		array(
+			'render_callback' => 'render_block_core_image',
+		)
+	);
+}
+add_action( 'init', 'register_block_core_image' );