Argu is a great library to read program arguments in F#.

But in case of modularization, is it possible somehow to merge different arguments without subcommands? Let’s say you have a bunch of command line backends, implemented as modules in one program: a POS cash register, a kitchen order viewer, and a customer database. Each of them may have their service arguments like network address to listen on and a port. And each of them have their own settings, a fixed waiter for the POS or sth like that.

My current implementation is

type ServiceArguments =
    | Rest_Service of RestHost: string * RestPort: uint16
    interface IArgParserTemplate with

type PosArguments =
    | [<AltCommandLine("-w")>] [<EqualsAssignmentOrSpaced>] Waiter of uint
    interface IArgParserTemplate with

type ClientArguments =
    | ServiceArguments of service: ServiceArguments 
    | PosArguments of pos: PosArguments
    interface IArgParserTemplate with

I assume there is some kind of interceptor function in Argu, which I could implement. Or should I collect all known arguments for each interface and then provide it to the sub modules? Or is the only way to use subcommands? Feels a bit strange, though.