Env Settings

Env Settings is a Rust library that helps you to initialize structs using environment variables

This Rust library took inspiration from pydantic's BaseSettings Python class

Installation

cargo add env-settings
cargo add env-settings-derive

Usage

When you add the EnvSettings derive to a struct, two methods are added to it

```
fn from_env() -> env_settings_utils::EnvSettingsResult<Self>
```
It creates a new instance using just the environment variables. If something fails, it returns an env_settings_utils::EnvSettingsError error
```
fn new(...) -> env_settings_utils::EnvSettingsResult<Self>
```
It creates a new instance using a combination of environment variables and parameters. More in detail, every field value can be passed as parameter wrapped in an Option object. Then if the parameter is Some, it is used, otherwise the value is recoved from the environment variables. If something fails, it returns an env_settings_utils::EnvSettingsError error

Basic

export name=paolo
export age=42

use env_settings_derive::EnvSettings;

#[derive(EnvSettings)]
struct MyStruct {
    name: String,
    age: u8,
}

fn main() {
    let my_struct = MyStruct::from_env().unwrap();
    assert_eq!(my_struct.name, "paolo".to_string());
    assert_eq!(my_struct.age, 42);

    let name = "luca";
    let my_struct = MyStruct::new(Some(name.to_string()), None).unwrap();
    assert_eq!(my_struct.name, name);
    assert_eq!(my_struct.age, 42);
}

Advanced

export STRUCT_NAME=paolo
echo "STRUCT_AGE=42\n" > .env

use env_settings_derive::EnvSettings;

#[derive(EnvSettings)]
#[env_settings(case_insensitive, file_path = ".env", prefix="STRUCT_")]
struct MyStruct {
    name: String,
    age: u8,
}

fn main() {
    let my_struct = MyStruct::from_env().unwrap();
    assert_eq!(my_struct.name, "paolo".to_string());
    assert_eq!(my_struct.age, 42);

    let name = "luca";
    let my_struct = MyStruct::new(Some(name.to_string()), None).unwrap();
    assert_eq!(my_struct.name, name);
    assert_eq!(my_struct.age, 42);
}

Parameters

The current supported parameters are:

case_insensitive: add it if the environment variables matching should be case insensitive
delay: add it to delay the lookup for environment variables from compilation time to run time
file_path: add it to specify a file path to read to add some environment variables (e.g. .env)
prefix: add it to specify a prefix to add to the name of the struct fields before matching the environment variables

Variables resolution hierarchy

Arguments passed to the new method (if using new).
Environment variables
Variables loaded from a file (e.g. .env)

Contribute

Before starting to work on a conribution please read:

Run tests

When testing run:

cargo test -- --test-threads=1

to prevent tests from competitively interacting with the same file

License

This project is licensed under the terms of the MIT or Apache 2.0 license.

env-settings 0.1.1