Serde Deserialize custom implementation

help
2

I would write this as:

impl Serialize for Filter {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: Serializer,
    {
        let mut s = String::new();

        if let Some(ref namespace_id) = self.namespace_id {
            s.push_str("namespace_id:");
            s.push_str(&namespace_id.to_string());
        }

        if let Some(ref object_id) = self.object_id {
            if !s.is_empty() {
                s.push_str(" AND ");
            }
            s.push_str("object_id:");
            s.push_str(&object_id);
        }

        s.serialize(serializer)
    }
}

impl<'de> Deserialize<'de> for Filter {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        let mut filter = Filter {
            namespace_id: None,
            object_id: None,
        };

        let s = String::deserialize(deserializer)?;
        for part in s.split(" AND ") {
            let mut kv = part.splitn(2, ":");
            match (kv.next(), kv.next()) {
                (Some("namespace_id"), Some(v)) => {
                    let uuid = Uuid::parse_str(v).map_err(de::Error::custom)?;
                    filter.namespace_id = Some(uuid);
                }
                (Some("object_id"), Some(v)) => {
                    filter.object_id = Some(v.to_owned());
                }
                _ => { /* report error if you want */ }
            }
        }

        Ok(filter)
    }
}