Customisable serialisation per field using serde's with attribute

[ghost]

Use case

Multiple services may use different methods for serialising numbers into JSON. Using the "features" feature, it's difficult to get the result you want, as adding the ability to serialise to arbitrary precision numbers may remove the ability to serialise to str numbers. The features are also not intuitive to set to achieve what you want. Multiple dependencies can also flight with eachother for which format should be the default.

Using Serde's with attribute allows developers to avoid these issues by setting the serialisation type per field, as well as keeping the features for backwards compatibility (and for setting a default if they wish).

Example (arbitrary) usage

Cargo.toml

[package]
name = "aaa"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
rust_decimal_macros = "1"
serde_json = "1"

[dependencies.rust_decimal]
features = ["serde-with-arbitrary-precision", "serde-with-float", "serde-with-str"]
git = "https://github.com/ShigotoMitame/rust-decimal"
branch = "serde-with"

[dependencies.serde]
version = "1"
features = ["derive"]

src/main.rs

use rust_decimal_macros::dec;
use rust_decimal::Decimal;
use serde::{Serialize, Deserialize};

fn main() {
    #[derive(Serialize, Deserialize)]
    struct ExampleUsage {
        #[serde(with = "rust_decimal::serde::arbitrary_precision")]
        pub ap_value: Decimal,
        #[serde(with = "rust_decimal::serde::float")]
        pub float_value: Decimal,
        #[serde(with = "rust_decimal::serde::str")]
        pub str_value: Decimal,
    }

    let example_value = ExampleUsage {
        ap_value: dec!(123.400),
        float_value: dec!(567.800),
        str_value: dec!(819.200),
    };
    let example_result = serde_json::to_string(&example_value).unwrap();
    assert_eq!(&example_result, r#"{"ap_value":123.400,"float_value":567.8,"str_value":"819.200"}"#);
}

[paupino]

This looks great and certainly makes sense to leverage. Do you mind running makers format on the code? It's a bit of a nit however it helps maintain a consistent style across the project.

[ghost]

Do you mind running makers format on the code? It's a bit of a nit however it helps maintain a consistent style across the project.

No problem -- slightly too used to having pre-commit stuff enabled. Do you want the branch rebased and the commits individually re-formatted? I've left it as a single fixing commit for now, but I don't mind either way.

I also updated the readme to document the new features.

[paupino]

Cool, thank you! No need to rebase - I'll squash the commits anyway.