How to get some useful datas when returning Result in async fn.

[RecordingTheSmile]

In the error_handling docs, the best way for returning error from async fn is Result:

use axum::http::StatusCode;

async fn handler() -> Result<String, StatusCode> {
    Err(StatusCode::NOT_FOUND)
}

In my application ,I defined a struct represents errors, and impl IntoResponse for it:

#[derive(Debug,Clone,serde::Serialize)]
struct MyError{
    message: String,
    // ... something else
}

impl IntoResponse for MyError{
    fn into_response(self) -> Response {
        (StatusCode::INTERNAL_SERVER_ERROR, Json(self)).into_response()
    }
}

Now, I want to return either Json or Html in MyError based on whether the request is sent by xhr. I found that I can't get any information abount request in MyError unless I pass to it:

#[derive(Debug,Clone,serde::Serialize)]
struct MyError{
    message: String,
    should_html: bool,
    // ... something else
}

// In async fn
// I defined a extractor here to judge if this request is made by xhr
async fn handler(IsXhr(is_xhr): IsXhr) -> Result<String, MyError> {
    Err(MyError{
        message: String::from("Something went wrong"),
        should_html: is_xhr
    })
}

Is this the only way I can do? Is there a method that does not require every async fn to judge whether it needs to return html?

[davidpdrsn]

Yep that's the only way. IntoResponse intentionally doesn't get access to the request data as that makes calling the .into_response() method inside handlers hard. I actually spoke about this during a talk I gave recently https://youtu.be/w1atdqNsA80?t=2013

[RecordingTheSmile]

Hmm, I see.
BTW, can I define a global error handler, then access request data and BoxError in this handler? I think this can avoid such repetitive work.

[davidpdrsn]

You can set an extension in your IntoResponse impl that's picked up by a middleware. Then the middleware can extract request data, detect if an error occurred, and return an appropriate response.

[RecordingTheSmile]

Thanks! I will try it!