how to validate a Option type with custom validate function?

[Silentdoer]

such as field1: Option<String>

[Keats]

It depends on the field type, if it's a struct, you can use require_nested like so: https://github.com/Keats/validator/blob/master/validator_derive_tests/tests/required.rs#L25-L28
I can't remember how that works for non structs though.