apply_block_hooks_to_content()

apply_block_hooks_to_content( string $content, WP_Block_Template|WP_Post|array|null $context = null, callable $callback = 'insert_hooked_blocks' ): string

function apply_block_hooks_to_content( $content, $context = null, $callback = 'insert_hooked_blocks' ) {
	// Default to the current post if no context is provided.
	if ( null === $context ) {
		$context = get_post();
	}

	$hooked_blocks = get_hooked_blocks();

	$before_block_visitor = '_inject_theme_attribute_in_template_part_block';
	$after_block_visitor  = null;
	if ( ! empty( $hooked_blocks ) || has_filter( 'hooked_block_types' ) ) {
		$before_block_visitor = make_before_block_visitor( $hooked_blocks, $context, $callback );
		$after_block_visitor  = make_after_block_visitor( $hooked_blocks, $context, $callback );
	}

	$block_allows_multiple_instances = array();
	/*
	 * Remove hooked blocks from `$hooked_block_types` if they have `multiple` set to false and
	 * are already present in `$content`.
	 */
	foreach ( $hooked_blocks as $anchor_block_type => $relative_positions ) {
		foreach ( $relative_positions as $relative_position => $hooked_block_types ) {
			foreach ( $hooked_block_types as $index => $hooked_block_type ) {
				$hooked_block_type_definition =
					WP_Block_Type_Registry::get_instance()->get_registered( $hooked_block_type );

				$block_allows_multiple_instances[ $hooked_block_type ] =
					block_has_support( $hooked_block_type_definition, 'multiple', true );

				if (
					! $block_allows_multiple_instances[ $hooked_block_type ] &&
					has_block( $hooked_block_type, $content )
				) {
					unset( $hooked_blocks[ $anchor_block_type ][ $relative_position ][ $index ] );
				}
			}
			if ( empty( $hooked_blocks[ $anchor_block_type ][ $relative_position ] ) ) {
				unset( $hooked_blocks[ $anchor_block_type ][ $relative_position ] );
			}
		}
		if ( empty( $hooked_blocks[ $anchor_block_type ] ) ) {
			unset( $hooked_blocks[ $anchor_block_type ] );
		}
	}

	/*
	 * We also need to cover the case where the hooked block is not present in
	 * `$content` at first and we're allowed to insert it once -- but not again.
	 */
	$suppress_single_instance_blocks = static function ( $hooked_block_types ) use ( &$block_allows_multiple_instances, $content ) {
		static $single_instance_blocks_present_in_content = array();
		foreach ( $hooked_block_types as $index => $hooked_block_type ) {
			if ( ! isset( $block_allows_multiple_instances[ $hooked_block_type ] ) ) {
				$hooked_block_type_definition =
					WP_Block_Type_Registry::get_instance()->get_registered( $hooked_block_type );

				$block_allows_multiple_instances[ $hooked_block_type ] =
					block_has_support( $hooked_block_type_definition, 'multiple', true );
			}

			if ( $block_allows_multiple_instances[ $hooked_block_type ] ) {
				continue;
			}

			// The block doesn't allow multiple instances, so we need to check if it's already present.
			if (
				in_array( $hooked_block_type, $single_instance_blocks_present_in_content, true ) ||
				has_block( $hooked_block_type, $content )
			) {
				unset( $hooked_block_types[ $index ] );
			} else {
				// We can insert the block once, but need to remember not to insert it again.
				$single_instance_blocks_present_in_content[] = $hooked_block_type;
			}
		}
		return $hooked_block_types;
	};
	add_filter( 'hooked_block_types', $suppress_single_instance_blocks, PHP_INT_MAX );
	$content = traverse_and_serialize_blocks(
		parse_blocks( $content ),
		$before_block_visitor,
		$after_block_visitor
	);
	remove_filter( 'hooked_block_types', $suppress_single_instance_blocks, PHP_INT_MAX );

	return $content;
}