README.md

serde-inline-default

Tiny crate to set default values for serde fields via inline attribute declaration.

Overview

This crate is an approach to do what serde-rs/serde#368 purposes. If you want to set default values in plain serde, you have to create a function and link to it with #[serde(default = "..."). This may be good if you need to do calculations to get the default value, but often you just want a simple integer or string to be the default value and have to create a whole function to return a hard-coded value.

#[derive(Deserialize)]
struct Test {
    #[serde(default = "value_default")]
    value: u32
}

fn value_default() -> u32 { 42 }

That can get quiet messy if you have many fields with many (different) default values. This crate tries to solve this issue by providing the #[serde_inline_default] proc macro. With this macro set at the struct level (before #[derive(Deserialize)]/#[derive(Serialize)]!, otherwise it's not working correctly), you can set default values via #[serde_inline_default(...)] for your serde fields inline, without creating an extra function.

#[serde_inline_default]
#[derive(Deserialize)]
struct Test {
    #[serde_inline_default(42)]
    value: u32
}

Internally, #[serde_inline_default(...)] gets expanded to a function which returns the set value and the attribute is replaced with #[serde(default = "<function name>")]. So this macro is just some syntax sugar for you, but can get quiet handy if you want to keep your code clean or write declarative macros / macro_rules!.

License

This project is licensed under either of the following licenses, at your option:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT License (LICENSE-MIT or http://opensource.org/licenses/MIT)