Since roxygen2 version 4.0.0, the @S3method tag has been deprecated in favour of using @export.
roxygen2
4.0.0
@S3method
@export
The package now t
As Mr Flick commented, appending the full function name to the roxygen line works correctly. If I change the line to:
#' @export check.arg
then the NAMESPACE file contains:
NAMESPACE
export(check.arg)