facet-validate

facet-validate

Field validation during deserialization for the facet ecosystem.

Features

• Validation runs during deserialization, so errors include source spans (e.g., pointing to the exact JSON location)
• Custom validators with meaningful error messages via Result<(), String>
• Auto-deref: fn(&str) validators work for String fields

Usage

use facet::Facet;
use facet_validate as validate;

fn validate_positive(n: &i64) -> Result<(), String> {
    if *n <= 0 {
        Err(format!("must be positive, got {}", n))
    } else {
        Ok(())
    }
}

#[derive(Facet)]
struct Product {
    #[facet(validate::custom = validate_positive)]
    price: i64,
}

Built-in Validators

Validator	Syntax	Applies To
min	validate::min = 0	numbers
max	validate::max = 100	numbers
min_length	validate::min_length = 1	String, Vec, slices
max_length	validate::max_length = 100	String, Vec, slices
email	validate::email	String
url	validate::url	String
regex	validate::regex = r"..."	String
contains	validate::contains = "foo"	String
custom	validate::custom = fn_name	any

Integration

Enable the validate feature on facet-json (or other format crates):

[dependencies]
facet-json = { version = "0.41", features = ["validate"] }
facet-validate = "0.41"

LLM contribution policy

Sponsors

Thanks to all individual sponsors:

...along with corporate sponsors:

...without whom this work could not exist.

Special thanks

The facet logo was drawn by Misiasart.

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.