vld

Type-safe runtime validation for Rust, inspired by Zod.

Describe the shape of your data once, parse untrusted input into typed Rust values, and get every problem back with its path and a stable error code. The same schemas produce JSON Schema / OpenAPI and plug into web frameworks, databases, queues, config and CLI crates.

Documentation: s00d.github.io/vld · API reference: docs.rs/vld

[dependencies]
vld = "0.5"

use vld::prelude::*;

vld::schema! {
    #[derive(Debug)]
    pub struct User {
        pub name: String => vld::string().trim().min(2).max(50),
        pub email: String => vld::string().email(),
        pub age: Option<u8> => vld::u8().min(18).optional(),
        pub tags: Vec<String> => vld::array(vld::string()).max_len(5).with_default(vec![]),
    }
}

fn main() {
    let user = User::parse(r#"{"name": " Ada ", "email": "ada@example.com"}"#).unwrap();
    assert_eq!(user.name, "Ada");

    let err = User::parse(r#"{"name": "A", "email": "nope", "age": 12}"#).unwrap_err();
    assert_eq!(err.issues.len(), 3); // every issue, not just the first
    println!("{err}");
    // .name: String must be at least 2 characters, received "A"
    // .email: Invalid email address, received "nope"
    // .age: Number must be at least 18, received 12
}

Features

• Schemas as values: strings with 40+ formats, exact sized integers, floats, dates (chrono, jiff or time), collections, tuples, unions, discriminated unions, refinements, transforms, recursive schemas.
• Typed structs with vld::schema! or #[derive(Validate)] (feature derive), serde renames, lenient parsing.
• Errors you can use: typed IssueCodes with stable keys, paths, received values, custom messages, flatten / treeify / prettify, bundled English, Russian, German and Spanish messages.
• JSON Schema and OpenAPI 3.1 from the same schemas (feature openapi), plus breaking-change detection (feature diff).
• Small core: only serde and serde_json by default; heavier validators are opt-in features.
• Integration crates for 10 web frameworks, OpenAPI tools, databases, queues, config, CLI and UI, with one error format and safe defaults (2 MiB body limits, 415 / 422 handling).

Crates

Minimum supported Rust version

The core crate needs Rust 1.85 with every feature. Some integration features need a newer compiler; see MSRV.md.

Contributing

See the contributing guide and the changelog. Upgrading from 0.4: migration guide.

License

MIT