#env #configuration #settings #environment #variables

macro envconf_derive

Boilerplate free initialization of structs from environment variables (derive crate)

1 unstable release

0.1.0 Nov 8, 2020

#4 in #variables

24 downloads per month
Used in envconf

MIT/Apache

6KB
126 lines

envconf

Rust Crates Docs License

Boilerplate free initialization of structs from environment variables

Usage

It is usual that programs rely on environment variables to define their behavior, especially for cloud and microservies applications. Imagine you need to setup a database connection by reading the following environment variables:

  • DB_HOST
  • DB_PORT
  • DB_USER
  • DB_PASSWORD
  • DB_NAME

With this library crate, it is as easy as this:

use envconf::{Setting, Error};

#[derive(Setting)]
struct DBSettings {
    #[conf(env = "DB_HOST", default = "localhost")]
    host: String,
    #[conf(env = "DB_PORT", default = 5432)]
    port: usize,
    #[conf(default = "myuser")]  // hardcoded setting
    user: String,
    #[conf(env = "DB_PASSWORD")] // env variable required
    password: String,
    #[conf(env = "DB_NAME", default = "mydb")]
    name: String,
}

fn main() -> Result<(), Error<'static>> {
    // This env is mandatory, so it needs to be set!
    std::env::set_var("DB_PASSWORD", "secret");

    // Initialize config from environment variables
    // Read the crate docs to check the possible Error variants
    let db_settings = DBSettings::init()?;

    assert_eq!(db_settings.host, "localhost");
    assert_eq!(db_settings.port, 5432);
    assert_eq!(db_settings.user, "myuser");
    assert_eq!(db_settings.password, "secret");
    assert_eq!(db_settings.name, "mydb");

    Ok(())
}

Contributing

If you find a vulnerability, bug or would like a new feature, open a new issue.

To introduce your changes into the codebase, submit a Pull Request.

Many thanks!

License

envconf is distributed under the terms of both the MIT license and the Apache License (Version 2.0).

See LICENSE-APACHE and LICENSE-MIT, and COPYRIGHT for details.

Dependencies

~350–780KB
~19K SLoC