type ObjectVersion struct {
	Object
	IsLatest  bool
	VersionID string `xml:"VersionId"`

	isDeleteMarker bool
}

// MarshalXML - marshal ObjectVersion
func (o ObjectVersion) MarshalXML(e *xxml.Encoder, start xxml.StartElement) error {
	if o.isDeleteMarker {
		start.Name.Local = "DeleteMarker"
	} else {
		start.Name.Local = "Version"
	}

	if err != nil {
		return ErrInvalidRetentionDate
	}

	*rDate = RetentionDate{retDate}
	return nil
}

// MarshalXML encodes expiration date if it is non-zero and encodes
// empty string otherwise
func (rDate RetentionDate) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
	if rDate.IsZero() {
		return nil
	}