General: Add allowed_blocks field to block registration and REST API

src/wp-admin/includes/post.php

@@ -2303,6 +2303,7 @@ function get_block_editor_server_block_settings() {
 		'keywords'         => 'keywords',
 		'example'          => 'example',
 		'variations'       => 'variations',
+		'allowed_blocks'   => 'allowedBlocks',
 	);
 
 	foreach ( $block_registry->get_all_registered() as $block_name => $block_type ) {

src/wp-includes/blocks.php

@@ -424,6 +424,7 @@ function register_block_type_from_metadata( $file_or_folder, $args = array() ) {
 		'styles'          => 'styles',
 		'variations'      => 'variations',
 		'example'         => 'example',
+		'allowedBlocks'   => 'allowed_blocks',
 	);
 	$textdomain        = ! empty( $metadata['textdomain'] ) ? $metadata['textdomain'] : null;
 	$i18n_schema       = get_block_metadata_i18n_schema();

src/wp-includes/class-wp-block-type.php

@@ -68,6 +68,14 @@ class WP_Block_Type {
 	 */
 	public $ancestor = null;
 
+	/**
+	 * Limits which block types can be inserted as children of this block type.
+	 *
+	 * @since 6.5.0
+	 * @var string[]|null
+	 */
+	public $allowed_blocks = null;
+
 	/**
 	 * Block type icon.
 	 *
@@ -303,6 +311,7 @@ class WP_Block_Type {
 	 *                                                   available when nested within the specified blocks.
 	 *     @type string[]|null $ancestor                 Setting ancestor makes a block available only inside the specified
 	 *                                                   block types at any position of the ancestor's block subtree.
+	 *     @type string[]|null $allowed_blocks           Limits which block types can be inserted as children of this block type.
 	 *     @type string|null   $icon                     Block type icon.
 	 *     @type string        $description              A detailed block type description.
 	 *     @type string[]      $keywords                 Additional keywords to produce block type as

src/wp-includes/rest-api/endpoints/class-wp-rest-block-types-controller.php

@@ -295,6 +295,7 @@ public function prepare_item_for_response( $item, $request ) {
 				'view_style_handles',
 				'variations',
 				'block_hooks',
+				'allowed_blocks',
 			),
 			$deprecated_fields
 		);
@@ -738,6 +739,17 @@ public function get_item_schema() {
 					'context'           => array( 'embed', 'view', 'edit' ),
 					'readonly'          => true,
 				),
+				'allowed_blocks'        => array(
+					'description' => __( 'Allowed child block types.' ),
+					'type'        => array( 'array', 'null' ),
+					'items'       => array(
+						'type'    => 'string',
+						'pattern' => self::NAME_PATTERN,
+					),
+					'default'     => null,
+					'context'     => array( 'embed', 'view', 'edit' ),
+					'readonly'    => true,
+				),
 			),
 		);
 

tests/phpunit/tests/rest-api/rest-block-type-controller.php

@@ -550,14 +550,15 @@ public function test_get_variation() {
 	 * @ticket 47620
 	 * @ticket 57585
 	 * @ticket 59346
+	 * @ticket 60403
 	 */
 	public function test_get_item_schema() {
 		wp_set_current_user( self::$admin_id );
 		$request    = new WP_REST_Request( 'OPTIONS', '/wp/v2/block-types' );
 		$response   = rest_get_server()->dispatch( $request );
 		$data       = $response->get_data();
 		$properties = $data['schema']['properties'];
-		$this->assertCount( 31, $properties );
+		$this->assertCount( 32, $properties );
 		$this->assertArrayHasKey( 'api_version', $properties );
 		$this->assertArrayHasKey( 'name', $properties );
 		$this->assertArrayHasKey( 'title', $properties );
@@ -577,6 +578,7 @@ public function test_get_item_schema() {
 		$this->assertArrayHasKey( 'example', $properties );
 		$this->assertArrayHasKey( 'variations', $properties );
 		$this->assertArrayHasKey( 'block_hooks', $properties );
+		$this->assertArrayHasKey( 'allowed_blocks', $properties );
 		$this->assertArrayHasKey( 'editor_script_handles', $properties );
 		$this->assertArrayHasKey( 'script_handles', $properties );
 		$this->assertArrayHasKey( 'view_script_handles', $properties );