Implement recursion checking in core/block (WordPress#26923)

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

@@ -6,27 +6,45 @@
  */
 
 /**
- * Renders the `core/block` block on server.
+ * Renders the `core/block` block on server if safe to do so.
  *
  * @param array $attributes The block attributes.
+ * @param string $content The block content.
+ * @param object $block The block being rendered.
  *
  * @return string Rendered HTML of the referenced block.
  */
-function render_block_core_block( $attributes ) {
+function render_block_core_block_safely( $attributes, $content, $block ) {
 	if ( empty( $attributes['ref'] ) ) {
 		return '';
 	}
+	if ( gutenberg_process_this_content( $attributes['ref'], $block->name ) ) {
+		$html = render_block_core_block( $attributes );
+		gutenberg_clear_processed_content();
+	} else {
+		$html = gutenberg_report_recursion_error();
+	}
+	return $html;
+}
 
-	$reusable_block = get_post( $attributes['ref'] );
-	if ( ! $reusable_block || 'wp_block' !== $reusable_block->post_type ) {
+/**
+ * Renders the `core/block` block on server.
+ *
+ * @param array $attributes The block attributes.
+ *
+ * @return string Rendered HTML of the referenced block.
+ */
+function render_block_core_block( $attributes ) {
+	$reusable_block = get_post($attributes['ref']);
+	if (!$reusable_block || 'wp_block' !== $reusable_block->post_type) {
 		return '';
 	}
 
-	if ( 'publish' !== $reusable_block->post_status || ! empty( $reusable_block->post_password ) ) {
+	if ('publish' !== $reusable_block->post_status || !empty($reusable_block->post_password)) {
 		return '';
 	}
 
-	return do_blocks( $reusable_block->post_content );
+	return( do_blocks($reusable_block->post_content) );
 }
 
 /**
@@ -36,7 +54,7 @@ function register_block_core_block() {
 	register_block_type_from_metadata(
 		__DIR__ . '/block',
 		array(
-			'render_callback' => 'render_block_core_block',
+			'render_callback' => 'render_block_core_block_safely',
 		)
 	);
 }