Crate serde_inline_default

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§serde-inline-default ci crates.io docs

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:

Attribute Macros§

  • serde_inline_default
    The main macro of this crate. Use it to define default values of fields in structs you Serialize or Deserialize. You do not need to create a extra function to provide the default value, as it is the case in serdes’ implementation of default (#[serde(default = "...")]).