Attempting to write an argparse clone in pure R (using R6 classes tho)

rargparse.R

#!/usr/bin/env Rscript

library(R6)
library(testthat)


Argument <- R6Class('Argument',
  public = list(
    flag = NA,
    help = NA,
    short_flag = NA,
    initialize = function(flag=NA, short_flag=NA, help=NA) {
      self$flag <- flag
      self$short_flag <- short_flag
      self$help <- help
    }
  )
)

ArgumentParser <- R6Class('ArgumentParser',
  public = list(
    arguments = NULL,
    description = NA,
    initialize = function(description=NA) {
      self$description <- description
    },
    add_argument = function(...) {
      arg <- Argument$new(...)

      # append argument to arguments
      self$arguments <- c(self$arguments, arg)
    },
    print_help = function() {

      if (!is.na(self$description)) {
        message(self$description)
        message()
      }

      for (argument in self$arguments) {
        message(
          paste(
            argument$flag, argument$short_flag, '    ', argument$help
            )
          )
      }
    }
  )
)


p <- ArgumentParser$new(description='this is a test of the rargparse system')

p$add_argument('--foo', '-f', help='asdf')
p$add_argument('--bar', '-b', help='asdf')


p$print_help()