created_at2021-03-21 02:51:04.130567
updated_at2024-03-20 09:27:08.329446
descriptionThe missing YAML 1.2 parser for rust
David Aguilar (davvid)




Development has moved to yaml-rust2

IMPORTANT The enhancements from this fork have been merged into yaml-rust2, the de-facto Rust YAML implementation.

All future development has moved to yaml-rust2. Users are advised to upgrade to yaml-rust2.

Upgrading to yaml-rust2

You can use yaml-rust2 as a drop-in replacement for yaml-rust by setting the package option to yaml-rust2 in your project's Cargo.toml.

yaml-rust = { version = "0.7", package = "yaml-rust2" }

The original README from yaml-rust-davvid follows below:


The missing YAML 1.2 implementation for Rust.

Build status crates.io docs.rs

yaml-rust is a pure Rust YAML 1.2 implementation, which enjoys the memory safety property and other benefits from the Rust language. The parser is heavily influenced by libyaml and yaml-cpp.

Quick Start

Add the following to the Cargo.toml of your project:

yaml-rust = { version = "0.6", package = "yaml-rust-davvid" }

Use yaml::YamlLoader to load the YAML documents and access it as Vec/HashMap:

use yaml_rust::{YamlLoader, YamlEmitter};

fn main() {
    let s =
    - list1
    - list2
    - 1
    - 2.0
    let docs = YamlLoader::load_from_str(s).unwrap();

    // Multi document support, doc is a yaml::Yaml
    let doc = &docs[0];

    // Debug support
    println!("{:?}", doc);

    // Index access for map & array
    assert_eq!(doc["foo"][0].as_str().unwrap(), "list1");
    assert_eq!(doc["bar"][1].as_f64().unwrap(), 2.0);

    // Chained key/array access is checked and won't panic,
    // returns BadValue if the key does not exist.

    // Dump the YAML object
    let mut out_str = String::new();
        let mut emitter = YamlEmitter::new(&mut out_str);
        emitter.dump(doc).unwrap(); // dump the YAML object to a String
    println!("{}", out_str);

Note that yaml_rust::Yaml implements Index<&'a str> & Index<usize>:

  • Index<usize> assumes the container is an Array
  • Index<&'a str> assumes the container is a string to value Map
  • otherwise, Yaml::BadValue is returned

If your document does not conform to this convention (e.g. map with complex type key), you can use the Yaml::as_XXX family API to access your documents.


  • Pure Rust
  • Ruby-like Array/Hash access API
  • Low-level YAML events emission

Specification Compliance

This implementation aims to provide YAML parser fully compatible with the YAML 1.2 specification. The parser can correctly parse almost all examples in the specification, except for the following known bugs:

  • Empty plain scalar in certain contexts

However, the widely used library libyaml also fails to parse these examples, so it may not be a huge problem for most users.


This library does not try to interpret any type specifiers in a YAML document, so there is no risk of, say, instantiating a socket with fields and communicating with the outside world just by parsing a YAML document.


  • Encoder
  • Tag directive
  • Alias while deserialization

Minimum Rust version policy

This crate's minimum supported rustc version is 1.31 (released with Rust 2018, after v0.4.3), as this is the currently known minimum version for regex as well.


Licensed under either of

at your option.


Fork & PR on Github.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


yaml-rust-davvid is a fork of the original, and now unmaintained yaml-rust parser by chyh1990.

Commit count: 339

cargo fmt