Codegen targetting nightly compiler

The codegen setup for a stable compiler is more complicated than it needs to be due to custom derives being unstable in the current version of Rust. However if you are using a nightly compiler anyway, you can use serde_derive which has a much simpler interface. This is a preview of what the future will look like once custom derives are stabilized.

Advantages of this approach: trivial to set up - just a #![feature(...)] line and an extern crate; none of the disadvantages of the stable approach.

Disadvantages of this approach: depends on an unstable Rust feature so it only works if you are building with a nightly compiler; this feature will be stabilized in Rust 1.15 in February 2017; stabilization is tracked in rust-lang/rust#35900.

Here is the Cargo.toml:

Cargo.toml

[package]
name = "my-crate"
version = "0.1.0"
authors = ["Me <user@rust-lang.org>"]

[dependencies]
serde = "0.8"
serde_derive = "0.8"
serde_json = "0.8"  # just for the example, not required in general

Note that it does not need a build script. Now the src/main.rs which uses Serde's custom derives:

src/main.rs

#[macro_use]
extern crate serde_derive;

extern crate serde_json;

#[derive(Serialize, Deserialize, Debug)]
struct Point {
    x: i32,
    y: i32,
}

fn main() {
    let point = Point { x: 1, y: 2 };

    let serialized = serde_json::to_string(&point).unwrap();
    println!("serialized = {}", serialized);

    let deserialized: Point = serde_json::from_str(&serialized).unwrap();
    println!("deserialized = {:?}", deserialized);
}

Here is the output:

$ cargo run
serialized = {"x":1,"y":2}
deserialized = Point { x: 1, y: 2 }