block_core_navigation_get_fallback_blocks(): array

1479function block_core_navigation_get_fallback_blocks() {1480	$page_list_fallback = array(1481		array(1482			'blockName'    => 'core/page-list',1483			'innerContent' => array(),1484			'attrs'        => array(),1485		),1486	);1487 1488	$registry = WP_Block_Type_Registry::get_instance();1489 1490	// If `core/page-list` is not registered then return empty blocks.1491	$fallback_blocks = $registry->is_registered( 'core/page-list' ) ? $page_list_fallback : array();1492	$navigation_post = WP_Navigation_Fallback::get_fallback();1493 1494	// Use the first non-empty Navigation as fallback if available.1495	if ( $navigation_post ) {1496		$parsed_blocks  = parse_blocks( $navigation_post->post_content );1497		$maybe_fallback = block_core_navigation_filter_out_empty_blocks( $parsed_blocks );1498 1499		// Normalizing blocks may result in an empty array of blocks if they were all `null` blocks.1500		// In this case default to the (Page List) fallback.1501		$fallback_blocks = ! empty( $maybe_fallback ) ? $maybe_fallback : $fallback_blocks;1502 1503		// Run Block Hooks algorithm to inject hooked blocks.1504		// We have to run it here because we need the post ID of the Navigation block to track ignored hooked blocks.1505		// TODO: See if we can move the apply_block_hooks_to_content_from_post_object() call1506		// before the parse_blocks() call further above, to avoid the extra serialization/parsing.1507		$markup          = serialize_blocks( $fallback_blocks );1508		$markup          = apply_block_hooks_to_content_from_post_object( $markup, $navigation_post );1509		$fallback_blocks = parse_blocks( $markup );1510	}1511 1512	/**1513	 * Filters the fallback experience for the Navigation block.1514	 *1515	 * Returning a falsey value will opt out of the fallback and cause the block not to render.1516	 * To customise the blocks provided return an array of blocks - these should be valid1517	 * children of the `core/navigation` block.1518	 *1519	 * @since 5.9.01520	 *1521	 * @param array[] $fallback_blocks default fallback blocks provided by the default block mechanic.1522	 */1523	return apply_filters( 'block_core_navigation_render_fallback', $fallback_blocks );1524}
When	Instructions	Calls it makes
always	18–19	`::WP_Block_Type_Registry(), ->is_registered(), ::WP_Navigation_Fallback(), apply_filters()`
always	45–47	`::WP_Block_Type_Registry(), ->is_registered(), ::WP_Navigation_Fallback(), parse_blocks(), block_core_navigation_filter_out_empty_blocks(), serialize_blocks(), apply_block_hooks_to_content_from_post_object(), parse_blocks(), apply_filters()`