Rust/Serde: serialize external struct to json camelcase

Gunnar Sundberg 0
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I am working on some code that takes a struct returned by an external library, serializes it to json, and serializes the json to protobuf using pbjson. The external library uses serde and implements Serialize, but the json that is returned is snake case. The problem is that pbjson is expecting the json to be camelcase.

How can I get a camelcase version of the serde json object? (ie configure the external library to use something like #[serde(rename_all = "camelCase")] or to convert the json keys to camelcase?)

Note: I am working with many remote structs that in total add up to almost 2k lines of code. I would like to avoid recreating these types locally if possible.

serde rust json
1 Answers

If I understand correctly, you want something like this? Basically you just need to turn the foreign items into items of your own type and then serialize those.

// foreign struct
#[derive(Serialize, Deserialize)]
struct Foreign {
    the_first_field: u32,
    the_second_field: String,
}

#[derive(Serialize)]
#[serde(rename_all = "camelCase")]
struct Mine {
    the_first_field: u32,
    the_second_field: String,
}

impl From<Foreign> for Mine {
    fn from(
        Foreign {
            the_first_field,
            the_second_field,
        }: Foreign,
    ) -> Self {
        Self {
            the_first_field,
            the_second_field,
        }
    }
}

fn main() {
    // only used to construct the foreign items
    let in_json = r#"[{"the_first_field": 1, "the_second_field": "second"}]"#;

    let foreign_items = serde_json::from_str::<Vec<Foreign>>(in_json).unwrap();

    let mine_items = foreign_items.into_iter().map(Mine::from).collect::<Vec<_>>();
    let out_json = serde_json::to_string(&mine_items).unwrap();

    println!("{}", out_json);  // [{"theFirstField":1,"theSecondField":"second"}]
}
BallpointBen0
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