Plugin: Ensure that Block Hooks work correctly after landing in WP core

lib/compat/wordpress-6.4/block-hooks.php

@@ -87,7 +87,6 @@ function gutenberg_add_hooked_blocks( $settings, $metadata ) {
 
 	return $settings;
 }
-add_filter( 'block_type_metadata_settings', 'gutenberg_add_hooked_blocks', 10, 2 );
 
 /**
  * Register a hooked block for automatic insertion into a given block hook.
@@ -256,7 +255,6 @@ function gutenberg_parse_and_serialize_block_templates( $query_result ) {
 
 	return $query_result;
 }
-add_filter( 'get_block_templates', 'gutenberg_parse_and_serialize_block_templates', 10, 1 );
 
 /**
  * Filters the block template object after it has been (potentially) fetched from the theme file.
@@ -279,7 +277,37 @@ function gutenberg_parse_and_serialize_blocks( $block_template ) {
 
 	return $block_template;
 }
-add_filter( 'get_block_file_template', 'gutenberg_parse_and_serialize_blocks', 10, 1 );
+
+/**
+ * Register the `block_hooks` field for the block-types REST API controller.
+ *
+ * @return void
+ */
+function gutenberg_register_block_hooks_rest_field() {
+	register_rest_field(
+		'block-type',
+		'block_hooks',
+		array(
+			'schema' => array(
+				'description'       => __( 'This block is automatically inserted near any occurence of the block types used as keys of this map, into a relative position given by the corresponding value.', 'gutenberg' ),
+				'patternProperties' => array(
+					'^[a-zA-Z0-9-]+/[a-zA-Z0-9-]+$' => array(
+						'type' => 'string',
+						'enum' => array( 'before', 'after', 'first_child', 'last_child' ),
+					),
+				),
+			),
+		)
+	);
+}
+
+// Install the polyfill for Block Hooks only if it isn't already handled in WordPress core.
+if ( ! function_exists( 'traverse_and_serialize_blocks' ) ) {
+	add_filter( 'block_type_metadata_settings', 'gutenberg_add_hooked_blocks', 10, 2 );
+	add_filter( 'get_block_templates', 'gutenberg_parse_and_serialize_block_templates', 10, 1 );
+	add_filter( 'get_block_file_template', 'gutenberg_parse_and_serialize_blocks', 10, 1 );
+	add_action( 'rest_api_init', 'gutenberg_register_block_hooks_rest_field' );
+}
 
 // Helper functions.
 // -----------------
@@ -345,27 +373,3 @@ function gutenberg_serialize_block( $block ) {
 function gutenberg_serialize_blocks( $blocks ) {
 	return implode( '', array_map( 'gutenberg_serialize_block', $blocks ) );
 }
-
-/**
- * Register the `block_hooks` field for the block-types REST API controller.
- *
- * @return void
- */
-function gutenberg_register_block_hooks_rest_field() {
-	register_rest_field(
-		'block-type',
-		'block_hooks',
-		array(
-			'schema' => array(
-				'description'       => __( 'This block is automatically inserted near any occurence of the block types used as keys of this map, into a relative position given by the corresponding value.', 'gutenberg' ),
-				'patternProperties' => array(
-					'^[a-zA-Z0-9-]+/[a-zA-Z0-9-]+$' => array(
-						'type' => 'string',
-						'enum' => array( 'before', 'after', 'first_child', 'last_child' ),
-					),
-				),
-			),
-		)
-	);
-}
-add_action( 'rest_api_init', 'gutenberg_register_block_hooks_rest_field' );

lib/compat/wordpress-6.4/class-gutenberg-rest-block-patterns-controller.php

@@ -27,6 +27,11 @@ class Gutenberg_REST_Block_Patterns_Controller extends Gutenberg_REST_Block_Patt
 	public function prepare_item_for_response( $item, $request ) {
 		$response = parent::prepare_item_for_response( $item, $request );
 
+		// Run the polyfill for Block Hooks only if it isn't already handled in WordPress core.
+		if ( function_exists( 'traverse_and_serialize_blocks' ) ) {
+			return $response;
+		}
+
 		$data = $response->get_data();
 
 		if ( empty( $data['content'] ) ) {

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

@@ -41,12 +41,12 @@ function render_block_core_pattern( $attributes ) {
 	}
 
 	$pattern = $registry->get_registered( $slug );
-	$content = _inject_theme_attribute_in_block_template_content( $pattern['content'] );
+	$content = $pattern['content'];
 
+	// Backward compatibility for handling Block Hooks and injecting the theme attribute in the Gutenberg plugin.
 	// This can be removed when the minimum supported WordPress is >= 6.4.
-	if ( defined( 'IS_GUTENBERG_PLUGIN' ) && IS_GUTENBERG_PLUGIN ) {
-		// TODO: In the long run, we'd likely want to have a filter in the `WP_Block_Patterns_Registry` class
-		// instead to allow us plugging in code like this.
+	if ( defined( 'IS_GUTENBERG_PLUGIN' ) && IS_GUTENBERG_PLUGIN && ! function_exists( 'traverse_and_serialize_blocks' ) ) {
+		$content = _inject_theme_attribute_in_block_template_content( $content );
 		$blocks  = parse_blocks( $content );
 		$content = gutenberg_serialize_blocks( $blocks );
 	}

phpunit/tests/blocks/renderHookedBlocks.php

@@ -1,7 +1,5 @@
 <?php
 
-use PHP_CodeSniffer\Generators\HTML;
-
 /**
  * Tests for hooked blocks rendering.
  *
@@ -12,6 +10,16 @@
  * @group blocks
  */
 class Tests_Blocks_RenderHookedBlocks extends WP_UnitTestCase {
+	public function set_up() {
+		parent::set_up();
+		add_filter( 'block_type_metadata_settings', 'gutenberg_add_hooked_blocks', 10, 2 );
+	}
+
+	public function tear_down() {
+		remove_filter( 'block_type_metadata_settings', 'gutenberg_add_hooked_blocks' );
+		parent::tear_down();
+	}
+
 	/**
 	 * @ticket 59313
 	 */