Raw identifier keywords

[michaelfairley]

Right now, serde_derive passes through the r# on raw identifiers when the identifier is a keyword.

For example (playground link)

#[derive(Serialize)]
struct Foo {
    r#type: i32,
    r#bar: i32
}

fn main() {
    let foo = Foo{ r#type: 3, r#bar: 12 };
    println!("{}", serde_json::to_string_pretty(&foo).unwrap());
}

prints

{
  "r#type": 3,
  "bar": 12
}

That r# on the r#type seems like it shouldn't be exposed downstream of serde, since the current-list-of-keywords-in-Rust is an implementation detail that serialization probably shouldn't care about. Currently, a bunch of the data format libraries that work with serde (e.g. ron) emit invalid data when provided with these raw identifiers, since they assume that field identifiers have a limited set of characters (that doesn't include #).

Unfortunately, the root of this issue is probably upstream of serde, and even writing a test case for this in this repo is tricky (since the test code has to be Rust 2018).

[dtolnay]

Interesting! This is a bug. That program should be printing "type": 3 instead of "r#type": 3.

Would you be interested in tracking down where this is going wrong and sending a PR? Otherwise I should be able to take a look later this week.

As a workaround, at least serde(rename = "...") seems to work but this shouldn't be necessary.

#[derive(Serialize)]
struct Foo {
    #[serde(rename = "type")]
    r#type: i32,
    r#bar: i32
}

[dtolnay]

I published 1.0.73 with this fix. Thanks! The code in the playground link will print:

{
  "type": 3,
  "bar": 12
}