libyang

A YANG parser and data-modeling library written in Rust.

YANG (RFC 7950) is the data modeling language used to describe configuration and state data for network management protocols such as NETCONF and RESTCONF. libyang parses YANG modules, resolves their dependencies, and turns them into a tree you can walk to drive configuration and validation.

Features

• RFC 7950 grammar, parsed with a parol-generated parser.
• Module loading with automatic import / include (submodule) resolution.
• typedef, grouping, identity, and union resolution.
• An Entry tree suitable for building config schemas and validators.

Installation

Add it to your Cargo.toml:

[dependencies]
libyang = "1"

Usage

Load a module by name from a search path, resolve its dependencies, and build the Entry tree:

use libyang::{to_entry, YangStore};

let mut store = YangStore::new();
store.add_path("yang"); // directory containing your .yang files

// Parse the module and everything it imports/includes.
store.read_with_resolve("ietf-bgp").expect("parse and resolve");
store.identity_resolve();

let module = store.find_module("ietf-bgp").expect("module found");
let entry = to_entry(&store, module);

println!("loaded module: {}", entry.name);

For low-level access, you can parse a single file into the grammar AST directly:

use libyang::yang;
use libyang::yang_grammar::YangGrammar;
use libyang::yang_parser::parse;

let input = std::fs::read_to_string("yang/ietf-bgp@2023-07-05.yang").unwrap();
let mut grammar = YangGrammar::new();
parse(&input, "ietf-bgp", &mut grammar).expect("parse");

let node = yang(grammar).expect("build node tree");

How it works

The pipeline runs in four stages:

1. Parse — YANG text is parsed by the parol-generated grammar into a YangGrammar AST.
2. AST — yang() converts the grammar tree into structured Node values.
3. Resolve — YangStore loads imports/includes, merges submodules, and resolves typedefs, groupings, and identities.
4. Entry — to_entry() produces an Entry tree for data modeling and validation.

Testing

cargo test

Integration tests live in tests/ and run against fixture modules in tests/yang/ and the standard modules in yang/.

License

Licensed under either of Apache License, Version 2.0 or MIT license at your option.