Unveiling RON, Rust's alternative to JSON

04 Apr 2023

The majority of developers know about JSON, JavaScript Object Notation, and its utility in everyday life. However, as the ‘J’ in the name implies, JSON was originally intended to be used in JavaScript, which means its limitations too.

A good example is from Rust, as a strongly typed language, suffers a bit from the incompatibility of types in a JSON object, although the communities have already solved the problems of parsing JSON to Rust’s through the crates.

It doesn’t differentiate a floating number from an integer one, for example.

This is an example from the serde_json, a crate used to perform JSON operations in Rust.

use serde::{Deserialize, Serialize};
use serde_json::Result;

#[derive(Serialize, Deserialize)]
struct Person {
    name: String,
    age: u8,
    phones: Vec<String>,
}

fn typed_example() -> Result<()> {
    // Some JSON input data as a &str. Maybe this comes from the user.
    let data = r#"
        {
            "name": "John Doe",
            "age": 43,
            "phones": [
                "+44 1234567",
                "+44 2345678"
            ]
        }"#;

    // Parse the string of data into a Person object. This is exactly the
    // same function as the one that produced serde_json::Value above, but
    // now we are asking it for a Person as output.
    let p: Person = serde_json::from_str(data)?;

    // Do things just like with any other Rust data structure.
    println!("Please call {} at the number {}", p.name, p.phones[0]);

    Ok(())
}

As we can see, the parsing from JSON just works, but it has some issues like non-differentiations between structures and maps, random order, or quoted fields. In order to solve these issues and others, RON comes into the field.

What is a RON?

A RON, what stands for Rust Object Notation, is the Rust version of JSON, designed to support all of Rust data, so structs, enums, tuples, arrays, generic maps, and primitive values, but it also its limitations.

This is an example of JSON and RON objects.

JSON

{
   "materials": {
        "metal": {
            "reflectivity": 1.0
        },
        "plastic": {
            "reflectivity": 0.5
        }
   },
   "entities": [
        {
            "name": "hero",
            "material": "metal"
        },
        {
            "name": "monster",
            "material": "plastic"
        }
   ]
}

RON

Scene( // class name is optional
    materials: { // this is a map
        "metal": (
            reflectivity: 1.0,
        ),
        "plastic": (
            reflectivity: 0.5,
        ),
    },
    entities: [ // this is an array
        (
            name: "hero",
            material: "metal",
        ),
        (
            name: "monster",
            material: "plastic",
        ),
    ],
)

Note the following advantages of RON over JSON:

The new format uses (..) brackets for heterogeneous structures (classes), while preserving the {..} for maps, and [..] for homogeneous structures (arrays). This distinction allows us to solve the biggest problem with JSON.

In the RON’s repository has some examples to view and try out, further information about the crate, tooling around and much more what you need to know about it.

In summary, RON (Rust Object Notation) emerges as a superior alternative to JSON, specifically tailored for Rust’s needs. Unlike JSON, RON supports Rust’s data types seamlessly and offers enhancements like trailing commas and comments for improved readability. Its ability to differentiate between various data structures resolves key limitations of JSON. With RON, Rust developers gain a more efficient and expressive tool for data serialization and interchange, promising enhanced productivity and code maintainability in the Rust ecosystem.

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