Envconfig

Build a config structure from environment variables in Rust without boilerplate.

Usage

Let's say you application relies on the following environment variables:

DB_HOST
DB_PORT

And you want to initialize Config structure like this one:

struct Config {
    host: String,
    port: u16,
}

You can achieve this with the following code without boilerplate:

#[macro_use]
extern crate envconfig_derive;
extern crate envconfig;

use envconfig::Envconfig;

#[derive(Envconfig)]
pub struct Config {
    #[envconfig(from = "DB_HOST")]
    pub db_host: String,

    #[envconfig(from = "DB_PORT", default = "5432")]
    pub db_port: u16,
}

fn main() {
    // Assuming the following environment variables are set
    std::env::set_var("DB_HOST", "127.0.0.1");

    // Initialize config from environment variables or terminate the process.
    let config = Config::init().unwrap();

    assert_eq!(config.db_host, "127.0.0.1");
    assert_eq!(config.db_port, 5432);
}

Running tests

Tests do some manipulation with environment variables, so to prevent flaky tests they have to be executed in a single thread:

cargo test -- --test-threads=1

Roadmap

- migrate to the latest versions of syn and quote
- support Option<T> (issue)
- support default attribute (issue)
- support nested structures?

License

Contributors