Customizing errors from Query extractor in Rust with Axum

Question

I have followed the example provided here to customize the extractor error for the Json extractor:

#[derive(FromRequest)]
#[from_request(via(axum::Json), rejection(ApiError))]
pub struct JsonExtractor<T>(pub T);

#[axum::debug_handler]
pub(crate) async fn create(
    state: State<AppState>,
    JsonExtractor(json): JsonExtractor<RouteBody>,
) -> Result<axum::Json<Customer>, ApiError>

This works great, but when I try the same for extracting from the Query, I get errors:

#[derive(FromRequest)]
#[from_request(via(axum::extract::Query), rejection(ApiError))]
pub struct QueryExtractor<T>(pub T);

#[axum::debug_handler]
pub(crate) async fn list(
    state: State<AppState>,
    query: QueryExtractor<RouteQuery>, // errors here
) -> Result<axum::Json<List<Customer>>, ApiError>

the trait bound `QueryExtractor<customers::list::RouteQuery>: FromRequest<AppState, hyper::Body, _>` is not satisfied
Function argument is not a valid axum extractor.

Answer 1

The difference is Json implements FromRequest while Query implements FromRequestParts (the latter doesn't consume the request body).

So you'd use #[derive(FromRequestParts) instead:

This works similarly to #[derive(FromRequest)] except it uses FromRequestParts. All the same options are supported.