serde-with-expand-env

Parse environment variables in serde crate using deserialize_with.

Example:

use std::env;
use serde_json;
use serde::Deserialize;
use serde_with_expand_env::with_expand_envs;

#[derive(Deserialize, Debug)]
struct Test {
    #[serde(deserialize_with="with_expand_envs")]
    number: usize,
    #[serde(deserialize_with="with_expand_envs")]
    string: String,
    #[serde(deserialize_with="with_expand_envs")]
    default: usize,
}

fn main() {
    let serialized = r#"{"number": "$NUMBER",
                         "string": "my string: $STRING",
                         "default": "${DEFAULT:-42}"
                      }"#;

    // No envs set will fail with enviroment variable not found
    assert_eq!(serde_json::from_str::<Test>(&serialized).is_err(), true);

    env::set_var("NUMBER", "42");
    env::set_var("STRING", "hacker");
    let deserialized: Test = serde_json::from_str(&serialized).unwrap();

    assert_eq!(deserialized.number, 42);
    assert_eq!(deserialized.string, "my string: hacker");
    assert_eq!(deserialized.default, 42);

    env::set_var("DEFAULT", "4200");
    let deserialized: Test = serde_json::from_str(&serialized).unwrap();
    assert_eq!(deserialized.default, 4200);

    // Invalid number
    env::set_var("NUMBER", "cuarentaydos");
    env::set_var("STRING", "42");
    assert_eq!(serde_json::from_str::<Test>(&serialized).is_err(), true);
}

more examples in examples