use serde::Deserialize;

use figment2::{Figment, providers::{Format, Toml, Json, Env}};

#[derive(Deserialize)]
struct Package {
    name: String,
    authors: Vec<String>,
    publish: Option<bool>,
    // ... and so on ...
}

#[derive(Deserialize)]
struct Config {
    package: Package,
    rustc: Option<String>,
    // ... and so on ...
}

let config: Config = Figment::new()
    .merge(Toml::file("Cargo.toml"))
    .merge(Env::prefixed("CARGO_"))
    .merge(Env::raw().only(&["RUSTC", "RUSTDOC"]))
    .join(Json::file("Cargo.json"))
    .extract()?;