length validation of bytes fields incorrectly converts to utf-8 string

[immesys]

What version of ogen are you using?

v1.2.1

Can this issue be reproduced with the latest version?

Yes

What did you do?

I have a field in an API object with format: bytes and a length requirement:

        key:
          type: string
          format: byte
          minLength: 256

This is generating code that looks like this in oas_validators_gen.go

func (s *KeyInfo) Validate() error {
	var failures []validate.FieldError
	if err := func() error {
		if err := (validate.String{
			MinLength:    256,
			MinLengthSet: true,
			MaxLength:    0,
			MaxLengthSet: false,
			Email:        false,
			Hostname:     false,
			Regex:        nil,
		}).Validate(string(s.Key)); err != nil {
			return errors.Wrap(err, "string")
		}
		return nil
	}(); err != nil {
		failures = append(failures, validate.FieldError{
			Name:  "key",
			Error: err,
		})
	}
	if len(failures) > 0 {
		return &validate.Error{Fields: failures}
	}
	return nil
}

This converts the byte array to a string and uses the string validator, which counts runes for length, not bytes:

func (t String) Validate(v string) error {
	if err := (Array{
		MinLength:    t.MinLength,
		MinLengthSet: t.MinLengthSet,
		MaxLength:    t.MaxLength,
		MaxLengthSet: t.MaxLengthSet,
	}).ValidateLength(len([]rune(v))); err != nil {
		return err
	}

Thus, this code is incorrect: there is no guarantee that this byte array is valid utf-8. In fact it is not, so I consistently get errors that the key is too short because it is counting utf-8 runes rather than counting bytes.

What did you expect to see?

I would expect validation of format: bytes fields to be done over bytes, not converting to utf-8 runes

What did you see instead?

I see consistently incorrect length validation for format: bytes fields