Macro serde_with::with_prefix

macro_rules! with_prefix {
    ($module:ident $prefix:expr) => { ... };
}

Serialize with an added prefix on every field name and deserialize by trimming away the prefix.

Example

The Challonge REST API likes to use prefixes to group related fields. In simplified form, their JSON may resemble the following:

{
  "player1_name": "name1",
  "player1_votes": 1,
  "player2_name": "name2",
  "player2_votes": 2
}

In Rust we would ideally like to model this data as a pair of Player structs, rather than repeating the fields of Player for each prefix.

struct Match {
    player1: Player,
    player2: Player,
}

struct Player {
    name: String,
    votes: u64,
}

This with_prefix! macro produces an adapter that adds a prefix onto field names during serialization and trims away the prefix during deserialization. An implementation of the Challonge API would use with_prefix! like this:

#[macro_use]
extern crate serde_derive;

#[macro_use]
extern crate serde_with;

extern crate serde_json;

#[derive(Serialize, Deserialize)]
struct Match {
    #[serde(flatten, with = "prefix_player1")]
    player1: Player,
    #[serde(flatten, with = "prefix_player2")]
    player2: Player,
}

#[derive(Serialize, Deserialize)]
struct Player {
    name: String,
    votes: u64,
}

with_prefix!(prefix_player1 "player1_");
with_prefix!(prefix_player2 "player2_");

fn main() {
    let m = Match {
        player1: Player {
            name: "name1".to_owned(),
            votes: 1,
        },
        player2: Player {
            name: "name2".to_owned(),
            votes: 2,
        },
    };

    let j = serde_json::to_string_pretty(&m).unwrap();
    println!("{}", j);
}