Adding support for actions

[Tezirg]

In the python version some other actions are supported for options. https://docs.python.org/3/library/optparse.html#defining-options
I'm thinking of the "append" and "count" options that are missing in this library but are often used in opt args parsing.

Is it possible to add support for these ?

[trevorld]

I probably won't take the time to add an append and count action since the practical use cases seem kind of rare and this is the first time in seven years someone has written to me about them. What kind of use case did you have in mind?

If a patch were submitted which doesn't break any of package unit tests then I would likely accept one. Note that optparse is currently a wrapper of the R package getopt (which I didn't write but now maintain) which currently throws an error for options specified multiple times).

Please note that if you don't mind a Python dependency there is also an R package argparse that is a wrapper of that Python package. In the python world optparse for several years has been deprecated in favor of argparse.

[Tezirg]

Thank you for the reply. I ended up using the argparse package as you suggested. It does support these additional actions.
I also went to try and add the support into this project, but It requires a patch in both optparse and getopt. Note that it doesn't throw when repeating a flag, it just overides with the last matched value.

Here is what I did using argparse so you can see a use case:

main <- function(ac, av) {
  parser <- ArgumentParser(description='R wrapper script')
  parser$add_argument("-i", "--input", dest="inputs", type="character", action="append", help="Input file")
  parser$add_argument("-s", "--script", dest="script", type="character", required=TRUE, help="User script file to run")
  parser$add_argument("-p", "--params", dest="params", type="character", default='{ "isDefault": true }', help="Configuration parameters in JSON format")
  args <- parser$parse_args(av);

  #Parse JSON input to native R data structure
  args$params <- fromJSON(args$params);
  #Import input script file
  source(args$script);
  #Call user script
  userJob(args$params, args$inputs);
}

#Getting command line arguments
cmdArgs <- commandArgs(trailingOnly = TRUE);
##Passing that to a c-like main function
main(42, c("-s", "template.R", "-i", "test1.csv", "-i", "test2.csv"));

Here is what a unit test for this could look like:

# Test extension for action support
context("Extended action parameters")
test_that("Make_option action='append'", {
    option_list3 <- list(
            make_option(c("-c", "--char"), type="character", action="append", help="Test flag or the character type"),
            make_option(c("-i", "--int"), type="integer", action="append", help="Test flag or the integer type")
    )
    parser <- OptionParser(usage = "%prog [options]", option_list = option_list3)
    args <- parse_args(parser, args = c("--char", "A", "-c", "B", "-c", "C", "-i", 42, "--int", 666))
    
    print("parsed")
    print(args)
    
    #Testing number of values in lists
    expect_equal(length(args$int), 2);
    expect_equal(length(args$char), 3);
    #Testing some values
    expect_equal(args$int[[1]], 42);
    expect_equal(args$char[[1]], "B");
})