Marking a struct field as flattened makes the struct ignore its tag

[jwillbold]

If I define a struct with a tag and add a field with the "flatten" attribute to this struct. The structs's tag seems to be ignored.

extern crate serde; // 1.0.84
#[macro_use]
extern crate serde_derive; // 1.0.84
#[macro_use]
extern crate serde_json; // 1.0.34


#[derive(Serialize, Debug)]
#[serde(tag="type")]
pub struct Program {
    #[serde(flatten)]
    pub body: ProgramType
}

#[derive(Serialize, Debug)]
#[serde(tag="sourceType", content="body")]
pub enum ProgramType {
    #[serde(rename="script")]
    Script(u64),
}


fn main() {
    let p = Program{body: ProgramType::Script(0)};
    // This assert fails, output:
    //  left: `Object({"body": Number(0), "sourceType": String("script")})`,
    //  right: `Object({"body": Number(0), "sourceType": String("script"), "type": String("Program")})`
    assert_eq!(serde_json::to_value(p).unwrap(),
                json!({"type": "Program", "sourceType": "script", "body": 0}))
}

[dtolnay]

Thanks! This looks like a bug. Would you be interested in sending a PR to fix it?

[jwillbold]

Sure. I implemented the tagged structs in the first place so I guess it's only fair if I have to do the bug fixing :D But it might take a few days.