Prevent string from being leaked by accident into output

no_display.rs

use std::fmt;
use core::fmt::Debug;
use clap::Parser;
use serde_with::{DeserializeFromStr, SerializeDisplay};

#[derive(Clone, SerializeDisplay, DeserializeFromStr)]
pub struct NoDisplay(String);

impl std::fmt::Display for NoDisplay {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    write!(f, "NoDisplay(*****)")
  }
}
impl Debug for NoDisplay {
  fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    write!(f, "NoDisplay(*****)")
  }
}

impl std::str::FromStr for NoDisplay {
  type Err = String;

  fn from_str(s: &str) -> Result<Self, Self::Err> {
    Ok(NoDisplay(s.to_string()))
  }
}

#[derive(Parser, Debug)]
pub struct Args {
  #[arg(long, value_parser = clap::value_parser!(NoDisplay))]
  pub my_sort_of_secret: NoDisplay,
}

fn main() {
  let args = Args::parse();

  // doesn't leak
  println!("{:?}", args);
  println!("{}", args.my_sort_of_secret);
  dbg!(&args);

  // leaks
  println!("{}", args.my_sort_of_secret.0);
}