Decodal/README.md

Decodal

Decodal is a small deterministic DSL for describing, composing, validating, and materializing structured data.

It is designed around a lightweight Rust library:

• host-supplied imports through SourceLoader
• no filesystem access in the library core
• concrete and abstract values with constraints and defaults
• deterministic expression evaluation
• optional regex support behind a Cargo feature
• browser playground support through WebAssembly

Library crate

Embedded hosts should depend on decodal and provide imports with a SourceLoader.

[dependencies]
decodal = "0.1"

Derive support

For embedded Rust applications, decodal-derive can generate a Decodal schema and typed decoder from a Rust struct.

[dependencies]
decodal = "0.1"
decodal-derive = "0.1"

use decodal::{DecodalDecode, DecodalSchema, Engine};
use decodal_derive::Decodal;

#[derive(Decodal)]
struct Service {
    name: String,
    #[decodal(gt = 443, default = 8443)]
    port: i64,
    #[decodal(rename = "feature.enable", default = true)]
    feature_enabled: bool,
}

The derive implements:

• DecodalSchema, which produces a host schema for Engine::bind_global
• DecodalDecode, which converts materialized Data into the Rust struct

CLI

A standalone CLI is kept in this repository as the decodal-cli workspace package. It builds a decodal binary, but it is not the primary crates.io package.

Run a Decodal file from the repository:

cargo run -q -p decodal-cli -- examples/advanced/main.dcdl

Enable optional regex support when needed:

cargo run -q -p decodal-cli --features regex -- examples/regex/main.dcdl

Web playground

The static documentation site and browser playground live under:

site/decodal-site/

License

Licensed under either of:

• Apache License, Version 2.0
• MIT license

at your option.