How to add clap's parsed args to Figment? I couldn't find a clap-provider

[abitofhelp]

Hello,

We use clap for our CLI applications. I am trying to integrate Figment into one of our clap apps for configuration management. I have everything working in the proper hierarchical order (for us: defaults < file < envvar < command-line). However, I cannot figure out how to feed clap's parsed command line args into Figment, and I couldn't find a clap-figment-provider anywhere. I am sure someone has resolved this question, but I couldn't find anything through Googling. I'd really appreciate your hints or explanations so I can move forward again. :P

I've simplified our app to a single parameter in order to figure out this issue. There is a single parameter: duration. Here is the struct, default, config.yaml, and builder(). Thank you for any suggestions and your time!

#[derive(Debug, Clone, PartialEq, Parser, Serialize, Deserialize)]
#[command(author, version, about, long_about = None, next_line_help = true)]
pub struct Arguments {
    /// The duration of an event
    #[arg(
    short  = 'd',
    long,
    env("DURATION"),
    value_parser = parse_duration,
    required = false
    )]
    #[serde(with = "humantime_serde")]
    pub duration: Option<Duration>,
}

/// Default Arguments
impl default::Default for Arguments {
    fn default() -> Self {
        Arguments {
            duration: Some(Duration::from_secs(10)),
        }
    }
}

impl Arguments {

    /// Build Arguments struct
    pub fn build() -> Result<Self, Box<dyn Error>> {

        let app: Command = Arguments::command();

        let config: Arguments = Figment::from(Serialized::defaults(Arguments::default()))
            .merge(Yaml::file("config.yaml"))
            .merge(Env::prefixed("FUN_"))
            // TODO: Merge and command line arguments
            // .merge(???))
            .extract()?;

        Ok(config)
    }
}

// config.yaml contents:
---
duration: 44s

// main.rs
fn main() -> Result<(), Box<dyn std::error::Error>> {
    let cfg: Arguments = Arguments::build()?;

    dbg!(cfg);
    Ok(())
}

fn parse_duration(arg: &str) -> Result<Duration, std::num::ParseIntError> {
    Ok(humantime::Duration::from_str(arg).unwrap().into())
}

[epage]

I do not have any experience with figment, so I can't speak too much to that. You'd likely need to parse your arguments into an ArgMatches which can be introspected. You might also need to carefully control the ids (implicitly the field's name) of your arguments.

Our conversation on layered configs is in #2763.

[abitofhelp]

Thank you for the help and the reference to the discussion!