Issues implementing middleware

[Cruxial0]

Summary

Hi, so I'm trying to add some functionality to my authentication middleware. This is the code I had before:

// Middleware to extract user from session token
pub async fn auth_middleware(
    cookies: CookieJar,
    State(state): State<Arc<AppState>>,
    mut request: Request,
    next: Next,
) -> Result<Response, StatusCode> {
    log::info!("auth middleware");
    let token = cookies.get("auth_token").and_then(|cookie| Some(cookie.value().to_string()));
    
    if token.is_none() {
        return Err(StatusCode::UNAUTHORIZED);
    }

    let mgr_write = state.user_manager.write().await;
    let token = token.unwrap();

    log::info!("token: {}", &token);
    let user = match mgr_write.validate_session(&token).await {
        Ok(u) => u,
        Err(_) => {
            return Err(StatusCode::UNAUTHORIZED);
        },
    };

    log::info!("user: {:#?}", user);
    
    request.extensions_mut().insert(user);
    Ok(next.run(request).await)
}

This works fine for me, but when I try to add some nested logic within the match statement:

Err(_) => {
    // Attempt auto-migration of session token
    let new_token = mgr_write.migrate_token(&token).await;
    match new_token {
        Ok(tok) => mgr_write.validate_session(&tok).await.unwrap(),
        Err(_) => return Err(StatusCode::UNAUTHORIZED),
    }
},

I get an error saying:

the trait bound `FromFn<..., ..., ..., _>: Service<...>` is not satisfied
the trait `tower_service::Service<axum::http::Request<axum::body::Body>>` is not implemented for `FromFn<fn(..., ..., ..., ...) -> ... {auth_middleware}, ..., ..., _>`
the following other types implement trait `tower_service::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

I assume this is due to how RwLocks work. I have tried different configurations such as limiting nesting and such, but the error seems persistent no matter what I do. The underlying datatype is as follows:

pub user_manager: Arc<RwLock<UserManager>>

And the concrete type isn't anything fancy either:

pub struct UserManager {
    db: Pool<Postgres>,
    data_dir: PathBuf,
}

Sorry if I'm missing anything obvious, but I've been at this for 3 hours at this point xd

axum version

0.8.3

[mladedav]

Try using debug_middleware, it might provide a better error.

[Cruxial0]

Oh that's helpful, thanks! The issue in this case was that I was returning Box<dyn std::error::Error> from my functions, which does not implement Send by default. After I fixed that it all worked.