Unable to differentiate None and Some(Value::Null)

[dariocurr]

As the following example shows, I am unable to differentiate between two different cases:

• when a null value is explicitly specified
• when a value that could be a Value is omitted

use serde::{Deserialize, Serialize};

#[derive(Debug, PartialEq, Serialize, Deserialize)]
struct MyStruct {
    value: Option<serde_json::Value>
}


fn main() {
    
    let my1: MyStruct =serde_json::from_str("{}").unwrap();
    assert_eq!(my1, MyStruct {value: None}); // OK

    let my2: MyStruct = serde_json::from_str("{\"value\": null}").unwrap();
    assert_eq!(my2, MyStruct {value: Some(serde_json::Value::Null)}); // Error
    
    
}

This happens because null is deserialized as None instead of Some(Value::Null)

[dariocurr]

Any news?

[dtolnay]

Hi @dariocurr, sorry that no one was able to provide guidance here. You could try taking this question to any of the resources shown in https://www.rust-lang.org/community, and someone will be able to help you get this working in the way you'd like.

[dariocurr]

IMHO this is a bug. Anyway, thank you, I'll find a solution 😎