support async validator

[LyunKi]

In some cases, we may need an async validator, so that we can call value.validate_async(xxx) which just like this js lib https://github.com/yiminghe/async-validator/

[IniterWorker]

Are you requesting to allow async fn call througth the custom field in validate macro ?

[bradleyess]

@IniterWorker - I'm here to suggest that async fn's can be used in custom derive annotations. I'm not sure where to start but would be happy to collaborate on it.

[paramako]

any progress on this?

[Keats]

None. A rewrite of the macro has landed on the next branch if someones wants to have a look.

[pintariching]

We should also think about if we want to be async framework agnistic or support just tokio or smol or others or all of them with features.

[DenuxPlays]

Any progress on this? Or any workaround that works with this crate: https://github.com/rambler-digital-solutions/actix-web-validator ? Supporting only non async methods makes this crate unusable for something like username validation if an async connection is used to the database.

[wsantos]

This is what I've been doing if I have a db/async validator, here is a dummy example, hope it helps until this is fixed.:

    #[derive(Deserialize, Validate)]
    pub struct SignupForm {
        #[validate(length(min = 3))]
        pub username: String,
        #[validate(email)]
        pub email: String,
    }

    let mut validation_errors = ValidationErrors::new();

    if let Err(form_validation_errors) = signup_form.validate() {
        validation_errors = form_validation_errors;
    }

    let user_result =
        User::create(&signup_form.username, &signup_form.email, &app_state.conn).await;

    if user_result.is_err() {
        validation_errors.add(
            "general",
            ValidationError::new("A user with this email or username already exists."),
        );
    } else {
        Token::send_auth_token_email(user_result.unwrap().id, &app_state.conn).await?;
    }