Support for #[validate(one_of(...))] for simple enum-like validations

[jonjsmith]

I’d like to have support for a #[validate(one_of(...))] attribute to simplify enum-like validations. Right now, I believe this can only be done in a custom function. A built-in validator like the following would be much cleaner.

#[validate(one_of("pending", "completed", "failed"))]
status: String

Similar functionality exists in marshmallow validate.OneOf

I’m open to feedback on this, but I wanted to see if this is something that would be aligned with the goals of this crate.

[Keats]

Wouldn't it make more sense in Rust to use enums and deserialize in that?

[jonjsmith]

Yes, deserializing enums with serde works for guarantee that you have a certain value, but if the input string doesn’t match any enum variant, serde returns a deserialization error but you can’t easily customize the error message like you can with #[validate(...)]. In other cases, I just want to check if the string is one of a few allowed values. Creating a separate enum just for validation can be unnecessary in some cases.