Is it as expect that Option attribute serialize into empty string instead of non-attribute.

[Vonfry]

A simple example here.

use serde::Serialize;
use quick_xml::se::to_string;

#[derive(Serialize)]
struct Foo {
    #[serde(rename = "@foo")]
    foo: Option<usize>
}

#[test]
fn test_foo() {
    let foo = Foo { foo: None };

    let foo_xml = to_string(&foo).unwrap();

    assert_eq!(foo_xml, "<Foo foo=\"\"/>");
    assert_eq!(foo_xml, "<Foo/>");
}

Is foo="" expected in quick-xml instead of dismissing this attribute?

[Mingun]

Yes, that is expected. This is the same behavior as in serde_json (yes, it is asymmetric de vs. ser). If you want to skip field serialization, add #[serde(skip_serializing_if = "Option::is_none")]. The documentation should be updated, although