How to compose transformations?

[jmcph4]

Consider two possible JSON responses from an API:

{
    "some_key": ""
}

{
    "some_key": "12.33"
}

Is there a way to apply both NoneAsEmptyString and DisplayFromStr?

#[serde_as]
#[derive(Clone, Debug, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct Response {
    #[serde_as(as = "NoneAsEmptyString")]
    #[serde_as(as = "DisplayFromStr")]
    pub some_key: Option<f64>,
}

[jonasbb]

Unfortunately it is impossible to combine multiple transformations. You can create you own type that implements the behavior of both combined. The documentation has some information how to get started and you can look at the implementation of both types.
https://docs.rs/serde_with/3.8.3/serde_with/guide/serde_as/index.html#implementing-serializeas--deserializeas