#[serde(rename_all = ...)] and #[serde(flatten)]

[neumann-paulmann]

Currently, newtype-wrapping an existing struct to change its naming scheme does not work:

use serde::{Deserialize, Serialize};
use serde_json; // 1.0.140

mod other_crate {
    use serde::{Deserialize, Serialize};

    #[derive(Debug, Default, Serialize, Deserialize)]
    pub struct Foo {
        does_frobnicate: bool,
    }
}

#[derive(Debug, Default, Serialize, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct MyFoo {
    #[serde(flatten)]
    inner: other_crate::Foo,
}

fn main() {
    let foo = other_crate::Foo::default();
    let s = serde_json::to_string(&foo).unwrap();
    assert_eq!(s, r#"{"does_frobnicate":false}"#);

    let my_foo = MyFoo::default();
    let my_s = serde_json::to_string(&my_foo).unwrap();
    assert_eq!(my_s, r#"{"doesFrobnicate":false}"#);
}

Playground

While I understand that changing this to the outcome, which I would expect could break existing user code, I suggest adding #[serde(rename_all = ...)] as a field attribute as well if and only if applied to a #[flatten]ed field.
This should apply recursively to all potentially nested structs withingthe flattened struct.