Custom handling of positional parameters

I would like to support some rich syntax with my CLI tool. I would like to allow the user to not only pass in a list of integers as positional arguments, but ranges of integers. I also don’t want to limit them on how these parameters are mixed together with the others.

Example:

foocli 1 2 4 6 8

Passes in the integer array [1,2,4,6,8] as positional arguments

foocli 1 3-5 2, 8

Passes in the integer array [1, 3, 4 5, 2, 8] as positional arguments.

I would ultimately like to support any range of numbers in any positional argument.

I know this is a rather special-purpose feature and that I can implement it myself using a list of string positional parameters, which I convert to integers myself. Any ideas on how to support it using a mix of picocli features and custom code would be nice.

[remkop]

I’m thinking the @Unmatched idea was also a workaround to begin with. What you really want is to be able to parse input that is a mixture of simple scalars and range expressions. I had another idea: why not use a custom converter?

class RangeConverter implements ITypeConverter<Set<Integer>> {
    // convert each argument to a set of integers;
    // first parse as scalar, if that fails, parse as range
}

Declare the field as a set of sets:

    @CommandLine.Parameters(arity="1..*")
    Set<Set<Integer>> viewIds;

And flatten the set in the application:

Set<Object> flat = 
    Set.stream()
        .flatMap(Set::stream)
        .collect(Collectors.toSet());

[remkop]

Let me take a look…