Required options

[imre-turi-cko]

Hey,

It's not really an issue, but a question.
Is there a way to set an option required?

Something like:

opt files in fileOption |> CommandOption.requiredAndExactlyOne

[cannorin]

It's possible but not very straightforward:

open FSharp.CommandLine

let inline exactlyOne (co: #ICommandOption<_>) =
    co |> CommandOption.zeroOrMore 
       |> CommandOption.map (function 
           | x :: [] -> x 
           | _ -> 
            let msg = sprintf "the option '%s' is required and should be provided only once"
                              (co.Summary.NameRepresentations |> List.head)
            OptionParseFailed (co.Summary, msg) |> raise
          )

Maybe worth adding to the library.