envoke

Envoke is a simple and ergonomic way to load environment variables into struct fields with minimal setup. With support for multiple ways to define environment variables with additional fallbacks, default values, custom parsing, validation, and nested structs for a cleaner interface.

Designed to be flexible and reduce boilerplate, all to make it easier to manage environment variables in your application.

Whats new?

This list!
Load environment variables from a .env file with the dotenv attribute—works on both structs and enums.
The new try_parse_fn attribute lets you use fallible parsing functions. Just like parse_fn, but it accepts a Result.

Useful links

Key features

Flexible Environment Variable Naming
Customize naming conventions with support for multiple environments, renaming, prefixes, and suffixes.
Versatile Default Values
Define defaults through type-based values, direct assignments, or function return values.
Pre-Assignment Parsing
Convert values into complex types before field assignment for enhanced data handling.
Comprehensive Validation
Validate values before and/or after assignment to ensure data integrity.
Structured Data Support
Seamlessly work with nested structs, enums, or standalone enums.
Built-in Sequence & Map Parsing
Effortlessly parse sequence and map-formatted strings for structured data.

Usage

Add to your Cargo.toml

[dependencies]

envoke = "0.3.0"

Example

use std::time::Duration;

use anyhow::Context;
use envoke::{Envoke, Error, Fill};

#[derive(Debug, Fill)]
#[fill(rename_all = "SCREAMING_SNAKE_CASE")]
struct Prod {
    #[fill(env)]
    api_port: u16,
}

#[derive(Debug, Fill)]
#[fill(rename_all = "SCREAMING_SNAKE_CASE")]
struct Development {
    #[fill(env)]
    api_port: u16,
}

#[derive(Debug, Fill)]
#[fill(rename_all = "UPPERCASE")]
enum Mode {
    Production(Production),
    Development(Development),
}

fn above_thirty(secs: &u64) -> anyhow::Result<()> {
    if *secs < 30 {
        anyhow::bail!("connect timeout cannot be less than 30 seconds, found {secs} second(s)")
    }

    Ok(())
}

fn to_duration(secs: u64) -> Duration {
  Duration::from_secs(secs)
}

#[derive(Debug, Fill)]
#[fill(rename_all = "SCREAMING_SNAKE_CASE")]
struct Environment {
    #[fill(nested)]
    mode: Mode,

    #[fill(env, default = Duration::from_secs(30))]
    #[fill(parse_fn = to_duration, arg_type = u64, validate_fn(before = above_thirty))]
    connect_timeout: Duration,
}

fn main() -> anyhow::Result<()> {
    let env =
        Environment::try_envoke().with_context(|| "An error occurred while loading environment");

    ...
}