Converting actix-web Responder to poem IntoResponse

[azzamsa]

Hi.

I am trying to convert this actix-web custom response into poem custom response

// actix

impl<T: Serialize> Responder for Response<T> {
    type Error = actix_web::error::Error;
    type Future = Ready<Result<HttpResponse, actix_web::error::Error>>;

    fn respond_to(self, req: &HttpRequest) -> Self::Future {
        Json(self).respond_to(req)
    }
}

This is my trial:

// poem

impl<T: Serialize> poem::IntoResponse for Response<T> {
    //type Error = actix_web::error::Error;
    //type Future = Ready<Result<poem::Response, poem::Error>>;

    fn into_response(self) -> poem::Response {
        poem::web::Json(self).into_response()
    }
}

and I got:

34  | impl<T: Serialize> poem::IntoResponse for Response<T> {
    |                    ^^^^^^^^^^^^^^^^^^ `T` cannot be sent between threads safely

I changed the output type from to Ready<Result<poem::Response, poem::Error>> but the error persist.

---

More context:

// handler.rs

#[handler]
pub async fn find_meta(
    ctx: Data<&Arc<ServerContext>>,
) -> Result<api::Response<model::Meta>, core::Error> {
    let meta = ctx.meta_service.find_meta().await?;
    Ok(api::Response::ok(meta.into()))
}

// api.rs

#[derive(Debug, Serialize, Deserialize)]
pub struct Response<T: Serialize> {
    data: Option<T>,
    #[serde(skip_serializing_if = "Option::is_none")]
    errors: Option<Vec<Error>>,
}

impl<T: Serialize> Response<T> {
    pub fn ok(data: T) -> Response<T> {
        return Response {
            data: Some(data),
            errors: None,
        };
    }

    pub fn err(err: crate::Error) -> Response<()> {
        match &err {
            _ => {}
        }

        return Response::<()> {
            data: None,
            errors: Some(vec![err.into()]),
        };
    }
}

impl<T: Serialize> poem::IntoResponse for Response<T> {
    //type Error = actix_web::error::Error;
    //type Future = Ready<Result<poem::Response, poem::Error>>;

    fn into_response(self) -> poem::Response {
        poem::web::Json(self).into_response()
    }
}

---

Sorry if the question is not related to Poem directly.
Thanks for Poem.

[sunli829]

impl<T: Serialize + Send> poem::IntoResponse for Response<T> {
   ...
}

[azzamsa]

The compiler told me the same thing. But I thought It was a mistake. Because it looks so complicated.

[azzamsa]

I have extracted my app into the smallest minimal working example.

I have ported this architecture into Poem + Async-GraphQL. Now I am porting it to Poem with REST API.

I am having hard time in the handler part.

// handler.rs

#[handler]
pub async fn find_meta(
    ctx: Data<&Arc<ServerContext>>,
) -> Result<api::Response<model::Meta>, core::Error> {

    let meta = ctx.meta_service.find_meta().await?;
    Ok(api::Response::ok(meta.into()))
}

I always get:

  --> src/meta/api/queries/find_meta.rs:10:1
   |
10 | #[handler]
   | ^^^^^^^^^^ the trait `IntoResult<_>` is not implemented for `Result<http::api::Response<model::Meta>, core::Error>`

Can I keep the output signature here? Or do you have better approach/design in that integrate well with Poem?

---

This is my app structure:

rest on  master [!] is 📦 v0.1.0 via 🦀 v1.58.1
❯ exa --git-ignore -T
.
├── Cargo.lock
├── Cargo.toml
├── Makefile
└── src
   ├── context.rs
   ├── errors
   │  ├── core.rs
   │  └── mod.rs
   ├── http
   │  ├── api.rs
   │  ├── error.rs
   │  └── mod.rs
   ├── lib.rs
   ├── main.rs
   └── meta
      ├── api
      │  ├── mod.rs
      │  └── queries
      │     ├── find_meta.rs
      │     └── mod.rs
      ├── entities.rs
      ├── mod.rs
      ├── model
      │  └── mod.rs
      └── service
         ├── find_meta.rs
         └── mod.rs

rest.zip

Thanks in advance.

[sunli829]

You don't implement ResponseError for crate::errors::core::Error, should you use crate::Error instead?

[azzamsa]

So, strange. It works out of the box after changing the output signature to create::Error instead. I just follow the upstream code. I will ask the upstream author regarding this.

To make sure that the error mechanism work, I changed the service code to:

modified   src/meta/service/find_meta.rs
@@ -7,6 +7,7 @@ impl Service {
             build: option_env!("VCS_REVISION").unwrap_or("unknown").to_string(),
             version: env!("CARGO_PKG_VERSION").to_string(),
         };
-        Ok(meta)
+        // Ok(meta)
+        Err(crate::Error::Internal("internal!".to_string()))
     }
 }

and it works.

The error code and body works.
I just need to fix this part

impl ResponseError for Error {
    // builds the actual response to send back when an error occurs
    fn as_response(&self) -> poem::Response {
        let res = Response::<String>::err(self.clone());
        poem::Response::builder().status(self.status()).body("TODO")
    }

    fn status(&self) -> StatusCode {
        match self {
            Error::Internal(_) => StatusCode::INTERNAL_SERVER_ERROR, // 500
        }
    }
}

Maybe I need to change pub fn err(err: crate::Error) -> Response<()> { into json output and use Body::from_json() in other side.

[azzamsa]

It works now

modified   src/http/error.rs
@@ -7,7 +7,9 @@ impl ResponseError for Error {
     // builds the actual response to send back when an error occurs
     fn as_response(&self) -> poem::Response {
         let res = Response::<String>::err(self.clone());
-        poem::Response::builder().status(self.status()).body("TODO")
+        poem::Response::builder()
+            .status(self.status())
+            .body(poem::Body::from_string(res))
     }

@@ -16,15 +16,17 @@ impl<T: Serialize> Response<T> {
         };
     }
 
-    pub fn err(err: crate::Error) -> Response<()> {
+    pub fn err(err: crate::Error) -> String {
         match &err {
             _ => {}
         }
 
-        return Response::<()> {
+        let resp = Response::<()> {
             data: None,
             errors: Some(vec![err.into()]),
         };
+        let resp: String = serde_json::to_string(&resp).unwrap();
+        return resp;
     }
 }

---

Thanks a lot Sunli, for taking time to help. You helped us so fast. So we don't have any bottleneck using Poem and Async-GrahpQL.
Sorry if I can't sponsor you currently. Thanks a lot.

Hope you are doing well there. :)