Unsure how to use Axum API for a JSON request with a varied response type

[erikschul]

I basically just want to receive a JSON request and return a JSON response or an error (statuscode, or possibly a Response).

But I'm getting this compile error

the trait bound `fn(axum::Json<http_server::AuthRequestV1>) -> impl futures_util::Future<Output = std::result::Result<impl axum::response::IntoResponse, (http::StatusCode, std::string::String)>> {http_server::auth}: axum::handler::Handler<_, _>` is not satisfied
the following other types implement trait `axum::handler::Handler<T, S>`:
  <axum::handler::Layered<L, H, T, S> as axum::handler::Handler<T, S>>
  <axum::routing::MethodRouter<S> as axum::handler::Handler<(), S>>

when trying to add the route

let app = axum::Router::new()
  .route("/auth", get(auth))
  //...

for the code

async fn auth(
    Json(payload): Json<AuthRequestV1>,
) -> Result<impl IntoResponse, (StatusCode, String)> {
}

or

async fn auth(Json(payload): Json<AuthRequestV1>) -> impl IntoResponse {
}

[jplatte]

Hey, have you seen the documentation on debugging handler type errors?

[erikschul]

@jplatte Thanks, that is very useful! Probably it would save more people time if this macro was used more visibly in examples.

The problem was that I hadn't implemented Deserialize:

#[derive(Serialize, Deserialize, Debug)]
pub struct AuthRequestV1 {
...