Issue with handler with generics and await #2870

sergeda · 2024-08-09T08:30:01Z

sergeda
Aug 9, 2024

Summary

I have this router function with generics:

trait Resolver: Clone {
    async fn resolve(&self, ip: &str) -> Result<String, AppError>;
}

#[derive(Clone)]
struct TestState<R: Resolver> {
    resolver: R,
}

pub fn test_route<
R: Resolver + Send + Sync + Clone + 'static
>(state: TestState<R>) -> Router {
    Router::new()
        .route(
        "/:lang([a-z]{{2}})/test",
        get(test_handler::<R>),
    ).with_state(state)
}

async fn test_handler<R: Resolver> (
    State(state): State<TestState<R>>
) -> Result<Response, AppError> {
        state.resolver.resolve("").await;
        Ok("test".into_response())
    }

This doesn't compile with error:

the trait bound `fn(axum::extract::State<TestState<R>>) -> impl futures::Future<Output = Result<axum::http::Response<axum::body::Body>, AppError>> {test_handler::<R>}: Handler<_, _>` is not satisfied
   --> src/routes.rs:93:13
    |
93  |         get(test_handler::<R>),
    |         --- ^^^^^^^^^^^^^^^^^ the trait `Handler<_, _>` is not implemented for fn item `fn(State<TestState<R>>) -> impl Future<Output = Result<Response<Body>, AppError>> {test_handler::<R>}`
    |         |
    |         required by a bound introduced by this call
    |
    = note: the full name for the type has been written to '/home/serg/rust_projects/hobby/target/debug/deps/hobby-0269a4e20c37d102.long-type-9779308206820938635.txt'
    = note: consider using `--verbose` to print the full type name to the console
    = note: Consider using `#[axum::debug_handler]` to improve the error message
    = help: the following other types implement trait `Handler<T, S>`:
              <IntoHandler<H, T, S> as Handler<T, S>>
              <Layered<L, H, T, S> as Handler<T, S>>
              <MethodRouter<S> as Handler<(), S>>
              <Or<L, R, Lt, Rt, S> as Handler<(M, Lt, Rt), S>>
note: required by a bound in `axum::routing::get`

But if I comment out line with await: state.resolver.resolve("").await
it compiles fine.

I can't use top_level_handler_fn because it doesn't support generics.

How to find out what else required to make this code compile? What is required to make handler with await work?

axum version

0.7.5

joebnb · 2024-08-13T14:09:06Z

joebnb
Aug 13, 2024

would share how your resolved，im also have this question

0 replies

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Issue with handler with generics and await #2870

sergeda Aug 9, 2024

Summary

axum version

Replies: 1 comment

joebnb Aug 13, 2024

sergeda
Aug 9, 2024

joebnb
Aug 13, 2024