cfg-rs: A Configuration Library for Rust Applications

Major Features

• One method to get all config objects, see get.
• Automatic derive config object, see FromConfig.
• Support default value for config object by auto deriving, see derived attr.
• Config value placeholder parsing, e.g. ${config.key}, see placeholder.
• Random config value, e.g. configuration.get::<u8>("random.u8") will get random u8 value.
• Support refreshable value type RefValue, it can be updated when refreshing.
• Support refresh Configuration.
• Easy to use, easy to add new config source, easy to organize configuration, see register_source.[^priority]

See the examples for general usage information.

[^priority]: Config order is determined by the order of registering sources, register earlier have higher priority.

Supported File Format

• Toml: toml, tml
• Yaml: yaml, yml
• Json: json

How to Initialize Configuration

• Use Predefined Source Configuration in One Line

use cfg_rs::*;
let configuration = Configuration::with_predefined().unwrap();
// use configuration.

See init for details.

• Customize Predefined Source Configuration Builder

use cfg_rs::*;
init_cargo_env!();
let configuration = Configuration::with_predefined_builder()
    .set_cargo_env(init_cargo_env())
    .init()
    .unwrap();
// use configuration.

See init for details.

• Organize Your Own Sources

use cfg_rs::*;
init_cargo_env!();
let mut configuration = Configuration::new()
    // Layer 0: Register cargo env config source.
    .register_source(init_cargo_env()).unwrap()
    // Layer 1: Register customized config.
    .register_kv("customized_config")
        .set("hello", "world")
        .finish()
        .unwrap();
    // Layer 2: Register random value config.
#[cfg(feature = "rand")]
{
configuration = configuration.register_random().unwrap();
}
    // Layer 3: Register all env variables `CFG_*`.
configuration = configuration.register_prefix_env("CFG").unwrap()
    // Layer 4: Register yaml file(Need feature yaml).
    .register_file("/conf/app.yaml", true).unwrap();

#[cfg(feature = "toml")]
{
    let toml = inline_source!("../app.toml").unwrap();
    configuration = configuration.register_source(toml).unwrap();
}

// use configuration.

See register_kv, register_file, register_random, register_prefix_env for details.