serde_default_utils

Overview

This is a simple set of functions to make your life easier while working with defaults in serde. Based on const generic parameters. Heavily inspired by discussions on issues about serde defaults, but mostly this one

Kudos

This is just a @JohnTheCoolingFan's proposed solution but available as crate and a macro that helps to generate another const generic function for any const generic type.

Example

    use serde_default_utils::*;
    use serde::{Deserialize, Serialize};

    const JSON: &str = r#"{"yes_or_no":false,"max":60,"delta":-77,"delimeter":"☀"}"#;
    const EMPTY_JSON: &str = r#"{}"#;
    const MAX: u32 = 7;

    #[derive(Serialize, Deserialize, Default)]
    struct Config {
        #[serde(default = "default_bool::<true>")]
        yes_or_no: bool,
        #[serde(default = "default_i16::<-3>")]
        delta: i16,
        // you can even use consts right here
        #[serde(default = "default_u32::<MAX>")]
        max: u32,
        #[serde(default = "default_char::<'☀'>")]
        delimeter: char,
    }

    fn main() {
        // existing json fields are not changed
        let config: Config = serde_json::from_str(JSON).unwrap();
        let s = serde_json::to_string(&config).unwrap();
        assert_eq!(r#"{"yes_or_no":false,"delta":-77,"max":60,"delimeter":"☀"}"#, &s);
        // if the field is not present - it is substituted with defaults
        let config: Config = serde_json::from_str(EMPTY_JSON).unwrap();
        let s = serde_json::to_string(&config).unwrap();
        assert_eq!(r#"{"yes_or_no":true,"delta":-3,"max":7,"delimeter":"☀"}"#, &s);
        // the default impl is just calling underlying type defaults unless you have a custom impl Default
        let config = Config::default();
        let s = serde_json::to_string(&config).unwrap();
        assert_eq!(r#"{"yes_or_no":false,"delta":0,"max":0,"delimeter":"\u0000"}"#, &s);
    }

License: MIT OR Apache-2.0