Axum Post method trait bound error

[juddbaguio]

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

Bug Report

Version: 0.6.2

Platform: stable-x86_64-pc-windows-msvc

Crates:

├── axum v0.6.20
│ ├── axum-core v0.3.4
│ ├── axum-macros v0.3.8 (proc-macro)

Description: Post Handler Trait Bound Error

I have come across of an Axum trait bound handler error:

error[E0277]: the trait bound `fn(axum::extract::State<std::sync::Arc<services::user_service::Context>>, axum::Json<domain::dto::user_dto::CreateUserDTO>) -> impl std::future::Future<Output = std::result::Result<axum::Json<domain::entities::User>, (axum::http::StatusCode, std::string::String)>> {api::users::create_user::handler}: axum::handler::Handler<_, _, _>` is not satisfied
   --> src\api\users\mod.rs:11:26
    |
11  |         .route("/", post(create_user::handler))
    |                     ---- ^^^^^^^^^^^^^^^^^^^^ the trait `axum::handler::Handler<_, _, _>` is not implemented for fn item `fn(axum::extract::State<std::sync::Arc<services::user_service::Context>>, axum::Json<domain::dto::user_dto::CreateUserDTO>) -> impl std::future::Future<Output = std::result::Result<axum::Json<domain::entities::User>, (axum::http::StatusCode, std::string::String)>> {api::users::create_user::handler}`
    |                     |
    |                     required by a bound introduced by this call
    |
    = help: the following other types implement trait `axum::handler::Handler<T, S, B>`:
              <axum::handler::Layered<L, H, T, S, B, B2> as axum::handler::Handler<T, S, B2>>
              <axum::routing::MethodRouter<S, B> as axum::handler::Handler<(), S, B>>

And this is my handler implementation:

#[debug_handler]
pub async fn handler(
    State(user_service): State<Arc<Context>>,
    Json(payload): Json<CreateUserDTO>,
) -> Result<Json<User>, (StatusCode, String)> {
    let res = user_service.create_user(payload).await;
    if res.is_err() {
        return Err((
            StatusCode::INTERNAL_SERVER_ERROR,
            res.err().unwrap().to_string(),
        ));
    }

    Ok(Json(res.unwrap()))
}

I am not sure where it went wrong since I correctly follow the order of extractors. Any guidance or solutions will be appreciated, thank you!

Edit:
More info on the Context struct:

#[derive(Clone)]
pub struct Context {
    manager: TransactionManager,
}

pub trait ThreadSafe: Send + Sync {}

impl ThreadSafe for Context {}

#[derive(Clone)]
pub struct TransactionManager {
    pg_pool: Pool<Postgres>,
}

impl ThreadSafe for TransactionManager {}

Edit: Service function (create_user) implementation, I am using launchbadge/sqlx as my database driver. If I resort to &Pool<Postgres> connection type, the error seems gone. This only happens when I try to run transactions,

[davidpdrsn]

Did you try https://docs.rs/axum/0.6.20/axum/attr.debug_handler.html?

[juddbaguio]

I already did and the debug handler didn't show some kind of errors.

[juddbaguio]

No errors were shown when I added the debug_handler macro

[juddbaguio]

hello @davidpdrsn , I added more info from my second investigation.

[juddbaguio]

I am going to close this discussion, considered as Resolve.

The issue found is in my users_repo::create_user which takes Acquire trait from sqlx and I have found that this trait is not implemented for Send.

I modified the db executor to be on Executor<'_,DB> trait which has supertrait of Send

[trchopan]

Hi @juddbaguio ,
I have the same issue using sqlite and axum. Do you mind explain more how did you resolve your issue?
Thank you.

[juddbaguio]

Hi, basically Axum handlers required all objects to have a 'Send' trait. You may need to check all your functions involved specifically from your db structs or anything else if they already auto implemented the 'Sync' trait.

[trchopan]

Thank you for explain.

For me, it may not the same issue as you but the order of the extractor was the cause.

When I try

I got this error

But if I put the extract::Json extractor at the end. It is compiled and works fine.