Tuple struct does not respect skip_serializing

[dtolnay]

#[macro_use]
extern crate serde_derive;

extern crate serde;
extern crate serde_json;

#[derive(Serialize, Debug)]
struct S(usize, #[serde(skip)] usize);

fn main() {
    let s = S(0, 0);
    let j = serde_json::to_string(&s).unwrap();
    println!("{}", j);
}

[0,0]

Open question: whether a tuple struct with all but one skipped field should be serialized as a tuple struct of length 1 or a newtype struct.

[konstin]

Newtype, please. The current behavior causes problems when using PhantomData<T>.

In my case I want to add another type to my custom url type, which can also be deserialized.

#[derive(Deserialize, Serialize)]
pub struct CustomUrl<T: DeserializeOwned> {
    #[serde(with = "url_serde")]
    url: Url,
    #[serde(skip)]
    url_type: PhantomData<T>
}

Is there any way to tell serde to treat the above as a newtype struct? The above code is currently failing as serde expects a tuple where there's actually a string.

[durka]

I hit this today trying to make a serializable enum with tuple struct variants containing unserializable fields. I can't do it because #[skip] is ignored.

[dtolnay]

Fixed in b4e51fc. It will continue to serialize as a tuple even if there is only one field. #1054 is tracking an attribute that would make types with a single serialized field serialize just like the underlying field.