`middleware::from_fn` fails if fn calls async fn with `&Request` argument #2571

dfaust · 2024-02-06T19:36:56Z

dfaust
Feb 6, 2024

I have looked for existing issues (including closed) about this

Bug Report

Version

axum v0.7.4
axum-core v0.4.3

Platform

Linux work 6.7.2-1-default #1 SMP PREEMPT_DYNAMIC Fri Jan 26 11:01:28 UTC 2024 (a52bf76) x86_64 x86_64 x86_64 GNU/Linux

Description

middleware::from_fn fails if the provided function calls another async function that takes &Request as argument.

I tried this code:

use axum::{
    extract::Request,
    http::StatusCode,
    middleware::{self, Next},
    response::Response,
    Router,
};

async fn auth(request: Request, next: Next) -> Result<Response, StatusCode> {
    get_token(&request).await;

    todo!()
}

async fn get_token(request: &Request) {
    todo!()
}

fn main() {
    Router::<()>::new().route_layer(middleware::from_fn(auth));
}

I got this compiler error:

error[E0277]: the trait bound `axum::middleware::FromFn<fn(axum::http::Request<axum::body::Body>, axum::middleware::Next) -> impl std::future::Future<Output = std::result::Result<axum::http::Response<axum::body::Body>, axum::http::StatusCode>> {auth}, (), axum::routing::Route, _>: tower_service::Service<axum::http::Request<axum::body::Body>>` is not satisfied
   --> src/main.rs:20:37
    |
20  |     Router::<()>::new().route_layer(middleware::from_fn(auth));
    |                         ----------- ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `tower_service::Service<axum::http::Request<axum::body::Body>>` is not implemented for `FromFn<fn(Request<Body>, Next) -> impl Future<Output = Result<Response<Body>, ...>> {auth}, ..., ..., ...>`
    |                         |
    |                         required by a bound introduced by this call
    |
    = help: the following other types implement trait `tower_service::Service<Request>`:
              axum::middleware::FromFn<F, S, I, (T1,)>
              axum::middleware::FromFn<F, S, I, (T1, T2)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6, T7)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6, T7, T8)>
            and 8 others
note: required by a bound in `axum::Router::<S>::route_layer`
   --> /home/daniel/.cargo/registry/src/index.crates.io-6f17d22bba15001f/axum-0.7.4/src/routing/mod.rs:296:21
    |
293 |     pub fn route_layer<L>(self, layer: L) -> Self
    |            ----------- required by a bound in this associated function
...
296 |         L::Service: Service<Request> + Clone + Send + 'static,
    |                     ^^^^^^^^^^^^^^^^ required by this bound in `Router::<S>::route_layer`

The error can be avoided by either changing the get_token function to be sync, or by not passing a reference to the request.

Answered by davidpdrsn

Feb 6, 2024

Passing &Request creates a future that is !Send (because Request<axum::body::Body> is !Sync, which Request is a typealias for).

So you either have to pass the request by value (ownership) or use request.into_parts() and pass things separately.

View full answer

davidpdrsn · 2024-02-06T20:55:10Z

davidpdrsn
Feb 6, 2024
Collaborator

Passing &Request creates a future that is !Send (because Request<axum::body::Body> is !Sync, which Request is a typealias for).

So you either have to pass the request by value (ownership) or use request.into_parts() and pass things separately.

2 replies

dfaust Feb 6, 2024
Author

Thanks for the explanation. Using into_parts is an interesting solution.

My main issue was, that the error message is not helpful. But then again that's probably not an issue with axum.

davidpdrsn Feb 6, 2024
Collaborator

My main issue was, that the error message is not helpful. But then again that's probably not an issue with axum.

Nope there unfortunately isn't anything we can do about that. Though #1993 will help, when I get around to finishing it.

leviwc · 2024-05-24T01:10:45Z

leviwc
May 24, 2024

I am having a problem with this from_fn + this span after:

.layer(
  TraceLayer::new_for_http()
      .make_span_with(|_request: Request<Body>| {
          tracing::info_span!(
              "user-data",
              id = tracing::field::Empty,
              int_id = tracing::field::Empty,
              email = tracing::field::Empty,
              banned = tracing::field::Empty
          )
      })
      .on_request(|request: Request<Body>, span: Span| {
          let maybe_user: Option<&User> = request.extensions().get();
          if let Some(user) = maybe_user {
              span.record("id", user.id.to_string().as_str());
              span.record("int_id", user.int_id);
              span.record("email", user.email.clone());
              span.record("banned", user.banned);
          }
      }),
  ),

The error disappears when removing the info
is there any work arounds? previously it was &Request and &Span here so I thought that maybe the problem from this thread
but even after removing it it still didn't work
Error:

error[E0277]: the trait bound `axum::middleware::FromFn<fn(http::Request<axum::body::Body>, axum::middleware::Next) -> impl futures::Future<Output = Result<impl IntoResponse, http::StatusCode>> {metrify}, (), Compression<Cors<axum::middleware::FromFn<fn(http::Request<axum::body::Body>, axum::middleware::Next) -> impl futures::Future<Output = Result<http::Response<axum::body::Body>, http::StatusCode>> {cspheaders_layer}, (), AddExtension<AddExtension<axum::middleware::FromFn<fn(http::Request<axum::body::Body>, axum::middleware::Next) -> impl futures::Future<Output = Result<http::Response<axum::body::Body>, http::StatusCode>> {auth}, (), tower_http::trace::Trace<Route, SharedClassifier<ServerErrorsAsFailures>, {closure@api-gateway/src/controller/http/mod.rs:212:45: 212:70}, {closure@api-gateway/src/controller/http/mod.rs:221:41: 221:77}>, _>, std::sync::Arc<PostgresStorage>>, std::sync::Arc<FirebaseTokenVerifier>>, _>>>, _>: Service<http::Request<axum::body::Body>>` is not satisfied
    |
201 |               .layer(
    |                ----- required by a bound introduced by this call
202 | /                 ServiceBuilder::new()
203 | |                     .layer(middleware::from_fn(metrify))
204 | |                     .layer(CompressionLayer::new())
205 | |                     .layer(cors)
...   |
229 | |                             }),
230 | |                     ),
    | |_____________________^ the trait `Service<http::Request<axum::body::Body>>` is not implemented for `FromFn<fn(Request<Body>, Next) -> impl Future<Output = Result<impl IntoResponse, StatusCode>> {metrify}, (), Compression<Cors<FromFn<fn(Request<Body>, Next) -> impl Future<Output = Result<Response<Body>, StatusCode>> {cspheaders_layer}, (), AddExtension<AddExtension<FromFn<..., ..., ..., ...>, ...>, ...>, ...>>>, ...>`
    |
    = help: the following other types implement trait `Service<Request>`:
              axum::middleware::FromFn<F, S, I, (T1, T2)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6, T7)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6, T7, T8)>
              axum::middleware::FromFn<F, S, I, (T1, T2, T3, T4, T5, T6, T7, T8, T9)>
            and 8 others

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middleware::from_fn fails if fn calls async fn with &Request argument #2571

dfaust Feb 6, 2024

Bug Report

Version

Platform

Description

Replies: 2 comments · 2 replies

davidpdrsn Feb 6, 2024 Collaborator

dfaust Feb 6, 2024 Author

davidpdrsn Feb 6, 2024 Collaborator

leviwc May 24, 2024

`middleware::from_fn` fails if fn calls async fn with `&Request` argument #2571

dfaust
Feb 6, 2024

Replies: 2 comments 2 replies

davidpdrsn
Feb 6, 2024
Collaborator

dfaust Feb 6, 2024
Author

davidpdrsn Feb 6, 2024
Collaborator

leviwc
May 24, 2024