Sertyp

Type-preserving serialization for Typst. Serialize Typst values and work with them in Rust WASM plugins using typed data structures.

What is this?

Sertyp bridges Typst and Rust for WASM plugin development. Instead of passing untyped bytes or parsing strings, you get:

• Typst package: Serialize any Typst value (colors, lengths, content, etc.)
• Rust library: Deserialize into typed structs with utility methods
• Full roundtrips: Lossless — serialize and deserialize without degradation and reconstruct displayble values in typst.

Example: Pass rgb(255, 128, 0) to a plugin, work with it as Color { space: RGB, components: [255, 128, 0] } in Rust, and return it back to typst. The color can then still be used as a real typst color.

Example

In Rust (plugin)

use wasm_minimal_protocol::*;
use sertyp::*;

#[cfg(target_arch = "wasm32")]
initiate_protocol!();

#[typst_func]
pub fn fibonacci<'a>(
    n: Integer,
) -> sertyp::Result<'a, Integer> {
    let n: i32 = match n.try_into() {
        Ok(n) => n,
        Err(_) => return Err("Invalid integer range".into()).into()
    };
    
    let (mut v0, mut v1) = (0, 1);
    for _ in 0..n {
        (v0, v1) = (v1, v0 + v1);
    }

    Ok(v1.into()).into()
}

In Typst

#import "@preview/sertyp:0.1.2";
#let fibonacci(n) = {
    let plugin = plugin("<...>.wasm");
    sertyp.call(plugin.fibonacci, n);
}

#assert(fibonacci(10) == 89)

Supported Types

• Primitives: bool, int, float, decimal, string, bytes, none, auto
• Collections: array, dictionary
• Visual: color (RGB, CMYK, OkLab, HSL, etc.), stroke, gradient, alignment
• Numeric: length, angle, ratio, fraction, duration, relative
• Content: content, label, symbol, regex
• Advanced: function, module, type, arguments, styles, datetime, version

See typst/README.md for the full list and examples.

Why Sertyp?

Typst's built-in WASM communication uses untyped bytes. You either:

• Parse repr() strings (fragile, loses structure)
• Use cbor.encode() directly (loses type information)
• Manually build serialization for each type

Sertyp provides:

• Type preservation: Lengths stay lengths, colors stay colors
• Structured access: Extract color components, decompose lengths, parse function names
• Zero boilerplate: Automatic serialization for all supported types

Documentation and further examples

• Typst package: API reference, examples
• Rust library: Data structures, common patterns, plugin development

Contributing

Issues and PRs welcome

Limitations

• Security: Deserialization uses eval() — only deserialize trusted data
• Dynamic types: context and runtime-dependent elements cannot be fully serialized
• Closures: Inline functions lose their captured state

See individual READMEs for details.