K9 parser and renderer for Gleam — compiles to BEAM and JavaScript.

What this is

k9_gleam is the Gleam implementation of the K9 configuration format. K9 is a self-validating component specification format with three graduated security levels: Kennel (data), Yard (contracts), Hunt (execution).

Because Gleam compiles to both Erlang bytecode (BEAM) and JavaScript, this single library works in Elixir/Erlang projects, Deno scripts, and browser applications — from the same source.

Quick start

Add to gleam.toml:

[dependencies]
k9_gleam = ">= 0.1.0"

Then:

import k9

case k9.parse(content) {
  Ok(doc) -> io.debug(doc)
  Error(err) -> io.println("Parse error: " <> err.message)
}

Cross-compilation

# Build for BEAM (Erlang/Elixir)
gleam build

# Build for JavaScript (Deno, Node, browser)
gleam build --target javascript

# Run tests on both targets
gleam test

Both produce identical behaviour — no platform-specific code paths.

Module layout

Module	Purpose
src/k9/parser.gleam	Recursive descent parser: parse(String) → Result(Document, ParseError)
src/k9/types.gleam	K9 type system: Document, Value, Key, Type, Metadata
src/k9/validation.gleam	Post-parse validation: duplicate keys, type consistency
src/k9.gleam	Public API: parse/1, render/1, validate/1
test/	Test suite exercised on both BEAM and JS targets

K9 security levels

Level	What it permits
Kennel (.k9)	Pure data. Safe to process from any source.
Yard (.k9.ncl, unevaluated)	Nickel contracts for typed validation. No shell access.
Hunt (.k9.ncl, signed)	Executable recipes. Requires a valid cryptographic signature.

K9 ecosystem

• k9-rs — Rust (reference implementation)

• k9_ex — Elixir

• k9-haskell — Haskell

• tree-sitter-k9 — Editor grammar

See EXPLAINME for implementation evidence and caveats.

License

This project is licensed under the Mozilla Public License, v. 2.0. See the LICENSE file for details.

SPDX-License-Identifier: CC-BY-SA-4.0

Author

Jonathan D.A. Jewell
j.d.a.jewell@open.ac.uk