Crate toml

Expand description

A serde-compatible TOML-parsing library

TOML itself is a simple, ergonomic, and readable configuration format:

[package]
name = "toml"
version = "0.4.2"
authors = ["Alex Crichton <alex@alexcrichton.com>"]

[dependencies]
serde = "1.0"

The TOML format tends to be relatively common throughout the Rust community for configuration, notably being used by Cargo, Rust’s package manager.

TOML values

A value in TOML is represented with the Value enum in this crate:

pub enum Value {
    String(String),
    Integer(i64),
    Float(f64),
    Boolean(bool),
    Datetime(Datetime),
    Array(Array),
    Table(Table),
}

TOML is similar to JSON with the notable addition of a Datetime type. In general, TOML and JSON are interchangeable in terms of formats.

Parsing TOML

The easiest way to parse a TOML document is via the Value type:

use toml::Value;

let value = "foo = 'bar'".parse::<Value>().unwrap();

assert_eq!(value["foo"].as_str(), Some("bar"));

The Value type implements a number of convenience methods and traits; the example above uses FromStr to parse a str into a Value.

Deserialization and Serialization

This crate supports serde 1.0 with a number of implementations of the Deserialize, Serialize, Deserializer, and Serializer traits. Namely, you’ll find:

Deserialize for Value
Serialize for Value
Deserialize for Datetime
Serialize for Datetime
Deserializer for de::Deserializer
Serializer for ser::Serializer
Deserializer for Value

This means that you can use Serde to deserialize/serialize the Value type as well as the Datetime type in this crate. You can also use the Deserializer, Serializer, or Value type itself to act as a deserializer/serializer for arbitrary types.

An example of deserializing with TOML is:

use serde_derive::Deserialize;

#[derive(Deserialize)]
struct Config {
    ip: String,
    port: Option<u16>,
    keys: Keys,
}

#[derive(Deserialize)]
struct Keys {
    github: String,
    travis: Option<String>,
}

fn main() {
    let config: Config = toml::from_str(r#"
        ip = '127.0.0.1'

        [keys]
        github = 'xxxxxxxxxxxxxxxxx'
        travis = 'yyyyyyyyyyyyyyyyy'
    "#).unwrap();

    assert_eq!(config.ip, "127.0.0.1");
    assert_eq!(config.port, None);
    assert_eq!(config.keys.github, "xxxxxxxxxxxxxxxxx");
    assert_eq!(config.keys.travis.as_ref().unwrap(), "yyyyyyyyyyyyyyyyy");
}

You can serialize types in a similar fashion:

use serde_derive::Serialize;

#[derive(Serialize)]
struct Config {
    ip: String,
    port: Option<u16>,
    keys: Keys,
}

#[derive(Serialize)]
struct Keys {
    github: String,
    travis: Option<String>,
}

fn main() {
    let config = Config {
        ip: "127.0.0.1".to_string(),
        port: None,
        keys: Keys {
            github: "xxxxxxxxxxxxxxxxx".to_string(),
            travis: Some("yyyyyyyyyyyyyyyyy".to_string()),
        },
    };

    let toml = toml::to_string(&config).unwrap();
}