Environment Variables

Toni applications read configuration from environment variables. The toni-config crate automates this with typed structs (see Config Module), but you can also access environment variables directly.

Direct access

use std::env;

let database_url = env::var("DATABASE_URL")
    .expect("DATABASE_URL must be set");

let port: u16 = env::var("PORT")
    .unwrap_or_else(|_| "3000".to_string())
    .parse()
    .expect("PORT must be a valid port number");

With dotenv

For local development, use the dotenv crate to load a .env file:

[dependencies]
dotenv = "0.15"

dotenv::dotenv().ok();  // loads .env if it exists, silently ignores if missing
let config = AppConfig::load()?;

.env file format

# .env
PORT=3000
HOST=127.0.0.1
DATABASE_URL=postgresql://localhost/myapp
JWT_SECRET=super-secret-key-at-least-32-chars
LOG_LEVEL=debug

Environment-specific configuration

A common pattern is to load a base config and then override specific values per environment:

# .env.development
LOG_LEVEL=debug
DATABASE_URL=postgresql://localhost/myapp_dev

# .env.production
LOG_LEVEL=error
DATABASE_URL=postgresql://prod-server/myapp

let env = std::env::var("APP_ENV").unwrap_or_else(|_| "development".to_string());
dotenv::from_filename(format!(".env.{env}")).ok();
dotenv::dotenv().ok();  // base .env as fallback

Provider value from environment

#[module(
    providers: [
        provider_value!(
            "DATABASE_URL",
            std::env::var("DATABASE_URL").expect("DATABASE_URL required")
        ),
        provider_value!(
            "PORT",
            std::env::var("PORT")
                .unwrap_or_else(|_| "3000".to_string())
                .parse::<u16>()
                .expect("PORT must be a number")
        ),
    ],
    exports: ["DATABASE_URL", "PORT"],
)]
pub struct EnvModule;