Config Module

The toni-config crate provides structured, type-safe configuration backed by environment variables. It integrates with the DI container so your configuration is injectable like any other service.

Installation

[dependencies]
toni = "0.2"
toni-config = "0.1"

Defining a configuration struct

Use the Config derive macro to create a typed configuration struct. Each field maps to an environment variable:

use toni_config::Config;

#[derive(Config, Clone)]
pub struct AppConfig {
    #[env("PORT", default = "3000")]
    pub port: u16,

    #[env("HOST", default = "127.0.0.1")]
    pub host: String,

    #[env("DATABASE_URL")]
    pub database_url: String,

    #[env("JWT_SECRET")]
    pub jwt_secret: String,

    #[env("LOG_LEVEL", default = "info")]
    pub log_level: String,
}

Fields with default are optional — if the environment variable isn't set, the default value is used. Fields without default are required; the application panics at startup if they're missing.

Registering and injecting

use toni_config::Config;

#[module(
    providers: [
        provider_value!("Config", AppConfig::load().expect("Invalid configuration")),
    ],
    exports: [
        "Config",
    ],
)]
pub struct ConfigModule;

Inject by token in services:

// Services inject the config by its token
// (custom token injection syntax — see Provider Patterns)

Nested configuration

Group related settings into nested structs:

#[derive(Config, Clone)]
pub struct DatabaseConfig {
    #[env("DATABASE_URL")]
    pub url: String,

    #[env("DATABASE_POOL_SIZE", default = "10")]
    pub pool_size: u32,

    #[env("DATABASE_TIMEOUT_MS", default = "5000")]
    pub timeout_ms: u64,
}

#[derive(Config, Clone)]
pub struct AppConfig {
    #[env("PORT", default = "3000")]
    pub port: u16,

    #[nested]
    pub database: DatabaseConfig,

    #[nested]
    pub auth: AuthConfig,
}

Validation

Enable the validation feature to run validator crate validation on your config at startup:

[dependencies]
toni-config = { version = "0.1", features = ["validation"] }
validator = { version = "0.20", features = ["derive"] }

use toni_config::Config;
use validator::Validate;

#[derive(Config, Clone, Validate)]
pub struct AppConfig {
    #[env("PORT", default = "3000")]
    #[validate(range(min = 1024, max = 65535))]
    pub port: u16,

    #[env("DATABASE_URL")]
    #[validate(url)]
    pub database_url: String,

    #[env("JWT_SECRET")]
    #[validate(length(min = 32))]
    pub jwt_secret: String,
}

// Load with validation
let config = AppConfig::load_and_validate()?;

If any constraint fails, the error is reported at startup before the server begins listening.

Loading configuration

AppConfig::load() reads environment variables from the process environment. To also load from a .env file, use the dotenv feature:

[dependencies]
toni-config = { version = "0.1", features = ["dotenv"] }

// .env file is loaded automatically when AppConfig::load() is called
let config = AppConfig::load()?;