serde_toon

Dynamic values

use serde_toon::toon;

fn main() -> Result<(), serde_toon::Error> {
    let data = toon!({
        "users": [
            {"id": 1, "name": "Alice"},
            {"id": 2, "name": "Bob"}
        ],
        "active": true
    });
    println!("{}", serde_toon::to_string(&data)?);
    Ok(())
}

See examples/dynamic_values.rs and examples/macro.rs.

Strict decoding

from_str is lenient. For untrusted or LLM-generated input, strict mode enforces the spec's validation rules and reports where the input went wrong:

use serde_toon::{from_str_with_options, DecodeOptions, Value};

fn main() {
    // The header declares 3 rows but only 2 follow.
    let input = "users[3]{id,name}:\n  1,Ada\n  2,Bob";
    let err = from_str_with_options::<Value>(input, DecodeOptions::strict()).unwrap_err();
    assert!(err.to_string().contains("line 1"));
}

See examples/strict_decoding.rs.

Features

• TOON spec v4.1, passing all 538 official conformance tests
• Full Serde integration: derives, enums, maps, Option, 128-bit integers
• Zero-copy decoding: &str fields borrow from the input
• Three decoding modes: strict, lenient, and compatible with 0.2 output
• Configurable delimiter (comma, tab, pipe) and indentation
• Errors with line and column
• No unsafe code; MSRV 1.70

Compatibility with 0.2

The Rust API is unchanged, but 0.3 writes spec-compliant TOON, so the serialized text differs: there are no [#N] markers, fields keep declaration order, and NaN becomes null. from_str still reads everything 0.2 wrote. See the changelog.

Performance

Encoding and decoding are 2-4.6x faster than 0.2 (changelog). Compared with the official toon-format crate (benches/vs_toon_format.rs):

Documentation

https://docs.rs/serde_toon

License

MIT OR Apache-2.0