Mapping from parsed args to another struct

[viperML]

Hello!

This is a simplified view of a problem I have with another app. I have 2 structs: ComplexArgs and Complex. ComplexArgs is used by clap_derive to parse some flags. But I want to transform this struct following some logic rules into Complex, which is what I really need through my app:

use clap::*;

#[derive(Debug, Parser)]
struct MyCli {
    // other flags
    #[arg(short)]
    a: bool,

    #[command(flatten)]
    complex: ComplexArgs,
}

#[derive(Debug)]
struct Complex {
    // ...
}

fn transform(args: ComplexArgs) -> Complex {
    todo!();
}

#[derive(Debug, Args)]
struct ComplexArgs {
    #[arg(short)]
    b: bool,
    #[arg(short)]
    c: bool,
    #[arg(short)]
    d: bool,
}


fn main() {
    let cli = MyCli::parse();
    println!("{cli:#?}");
}

Currently, I parse into ComplexArgs, but what I really need through my application is the Complex struct.

It would be easier for me to have clap perform the transforming, such that MyCli gets a Complex, parsed as a ComplexArgs and then transformed:

#[derive(Debug, Parser)]
struct MyCli {
    #[arg(short)]
    a: bool,

    #[command(flatten)]
    // parse a a ComplexArgs and use transform?
    complex: Complex,
}

#[derive(Debug)]
// parse as a ComplexArgs and use transform?
struct Complex {
    // ...
}

This might be a very niche situation, but I might as well try to ask :)

[viperML]

I think manually implementing FromArgMatches and Args for my type is the way to go, as described in https://docs.rs/clap/latest/clap/_derive/index.html#flattening-hand-implemented-args-into-a-derived-application