JSON: Field names should account for r#

[fosskers]

Bug Report

Version

0.3.18

Platform

Linux caddi 6.10.3-arch1-2 #1 SMP PREEMPT_DYNAMIC Tue, 06 Aug 2024 07:21:19 +0000 x86_64 GNU/Linux

Description

Rust allows us to give struct fields the same name as reserved keywords, such as type, if we prefix that name with r#, as shown here:

struct Thing {
    amount: u32,
    r#type: String,
}

When serializing this into JSON via serde, we see the r# ignored in the output:

#[derive(Debug, serde::Serialize)]
struct Thing {
    amount: u32,
    r#type: String,
}

fn main() {
    let c = Thing {
        amount: 1,
        r#type: "hi".to_string(),
    };

    let json = serde_json::to_string(&c).unwrap();
    println!("{json}");
}

{"amount":1,"type":"hi"}

However, the JSON support within tracing-subscriber does not do this, instead rendering the field name as r#type.

Suggestion: it should account for any field names that start with r# and avoid rendering that piece.

[mladedav]

The JSON subscriber uses serde internally so the output should be the same.

Are you maybe using valuable? That would change how the serialization works and I've noticed you were using it in other recent issues.

[fosskers]

Yes, using valuable in this case. Is there a way to not use valuable and have the Serialize impl just do everything?

[mladedav]

I don't think so, you'd need a copy of the fmt subscriber without the valuable feature.

But in this case I think this should be fixed in valuable itself.

[fosskers]

So it might not be how the tracing-subscriber JSON formatter is rendering the field name, but how valuable is reporting the field name to begin with?