dynamic-config 0.3.0

Hot-reloadable, lock-free application configuration with a one-attribute API, built on figment.
Documentation 
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//! Writing configuration back out, and reading keys with no field.
//!
//! ```text
//! cargo run -p dynamic-config --example persistence --features json
//! ```

use dynamic_config::{dynamic_config, Format};
use serde::{Deserialize, Serialize};

#[dynamic_config]
#[derive(Debug, Deserialize, Serialize)]
struct ServerConfig {
    host: String,
    port: u16,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let sources = ServerConfig::builder("server").file("dynamic-config/examples/app.json");

    let mut config = sources.load()?;
    println!("loaded: {config:?}");

    // A CLI persisting a preference. The write is atomic — temporary file and
    // rename — because a watcher is very likely watching that directory, and a
    // partial file would look exactly like a broken edit.
    config.port = 9090;

    let path = std::env::temp_dir().join("dynamic-config-example.json");
    dynamic_config::save(&config, &path, Format::Json, "server")?;

    println!("\nwrote {}:", path.display());
    println!("{}", std::fs::read_to_string(&path)?);
    println!("Nested under the section key, so it reads straight back in.");

    // Reading keys the struct does not name: a plugin's table, a user-defined
    // section, anything whose shape is not known at compile time.
    let snapshot = sources.snapshot()?;

    println!("\nreading without a struct:");
    println!("  host        = {}", snapshot.get::<String>("host")?);
    println!("  contains(x) = {}", snapshot.contains("nothing_here"));

    std::fs::remove_file(&path)?;

    Ok(())
}