i18n Integration with es-fluent

koruma can integrate with es-fluent to localise validation errors. Enable the fluent feature and add the matching es-fluent dependency:

[dependencies]
koruma = { version = "*", features = ["derive", "fluent"] }
es-fluent = { version = "*", features = ["derive"] }

This setup assumes:

• koruma is built with derive + fluent.
• your es-fluent manager is initialized.
• a locale is selected before rendering messages.

Validators intended for localisation derive EsFluent. When the validated value needs custom conversion, annotate it with #[fluent(value(|x| ...))]. Then derive KorumaAllFluent on the consumer type.

use es_fluent::{EsFluent, ToFluentString as _};
use koruma::{Koruma, KorumaAllFluent, Validate, validator};

#[validator]
#[derive(Clone, Debug, EsFluent)]
pub struct IsEvenNumberValidation<
    T: Clone + Copy + std::fmt::Display + std::ops::Rem<Output = T> + From<u8> + PartialEq,
> {
    #[koruma(value)]
    #[fluent(value(|x: &T| x.to_string()))]
    pub actual: T,
}

impl<T: Copy + std::fmt::Display + std::ops::Rem<Output = T> + From<u8> + PartialEq> Validate<T>
    for IsEvenNumberValidation<T>
{
    fn validate(&self, value: &T) -> bool {
        *value % T::from(2u8) == T::from(0u8)
    }
}

#[validator]
#[derive(Clone, Debug, EsFluent)]
pub struct NonEmptyStringValidation {
    #[koruma(value)]
    pub input: String,
}

impl Validate<String> for NonEmptyStringValidation {
    fn validate(&self, value: &String) -> bool {
        !value.is_empty()
    }
}

#[derive(Koruma, KorumaAllFluent)]
pub struct User {
    #[koruma(IsEvenNumberValidation::<_>)]
    pub id: i32,

    #[koruma(NonEmptyStringValidation)]
    pub username: String,
}

let user = User { id: 3, username: "".to_string() };
if let Err(errors) = user.validate() {
    if let Some(id_err) = errors.id().is_even_number_validation() {
        println!("{}", id_err.to_fluent_string());
    }

    if let Some(username_err) = errors.username().non_empty_string_validation() {
        println!("{}", username_err.to_fluent_string());
    }

    for failed in errors.id().all() {
        println!("{}", failed.to_fluent_string());
    }

    for failed in errors.username().all() {
        println!("{}", failed.to_fluent_string());
    }
}

KorumaAllFluent gives you an all() iterator whose elements can be converted with ToFluentString. Initialise your i18n manager and select a locale before rendering localised messages.