validate_file_to_edit( string $file, string[] $allowed_files = array() )

Source

File: wp-admin/includes/file.php

function validate_file_to_edit( $file, $allowed_files = array() ) {
	$code = validate_file( $file, $allowed_files );

	if ( ! $code ) {
		return $file;
	}

	switch ( $code ) {
		case 1:
			wp_die( __( 'Sorry, that file cannot be edited.' ) );

			// case 2 :
			// wp_die( __('Sorry, can’t call files with their real path.' ));

		case 3:
			wp_die( __( 'Sorry, that file cannot be edited.' ) );
	}
}