website/content/actix-web-import-issue.md

title	date
Solving `app_data` or `ReqData` missing in requests for actix-web	2022-03-26

This post is day 5 of me taking part in the #100DaysToOffload challenge.

I'm using actix-web to set up a web server, and I've been hitting a small problem that I think other people may come across too.

To explain the problem, let me talk a bit about my setup. I have a custom middleware that checks if a user is authorized to access a route. It looks like this:

impl<S: 'static, B> Service<ServiceRequest> for CheckLoginMiddleware<S>
where
    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error>,
    S::Future: 'static,
{
    type Response = ServiceResponse<EitherBody<B>>;
    type Error = Error;
    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;

    dev::forward_ready!(service);

    fn call(&self, req: ServiceRequest) -> Self::Future {
        let state = self.state.clone();
        let (request, payload) = req.into_parts();
        let service = self.service.clone();

        let user_token = get_token_from_header(&request);
        let path_token = if self.allow_path_tokens {
            get_token_from_query(&request)
        } else {
            None
        };

        Box::pin(async move {
            match verify_auth(state, user_token, path_token, request.path()).await {
                Ok(authorized) => {
                    tracing::debug!("Request authorized, inserting authorization token");
                    // This is the "important bit" where we insert the authorization token into the request data
                    request.extensions_mut().insert(authorized);
                    let service_request =
                        service.call(ServiceRequest::from_parts(request, payload));
                    service_request
                        .await
                        .map(ServiceResponse::map_into_left_body)
                }
                Err(err) => {
                    let response = HttpResponse::Unauthorized().json(err).map_into_right_body();

                    Ok(ServiceResponse::new(request, response))
                }
            }
        })
    }
}

The verify_auth function is omitted, but the gist of it is that it returns an Result<Authorized, Error>. If the user is authorized, the authorization token verify_auth returned is then attached to the request.

Then here's how I use it in a path:

#[delete("/{store}/{path:.*}")]
async fn delete_storage(
    params: web::Path<(String, String)>,
    // This parameter is automatically filled with the token
    authorized: Option<ReqData<Authorized>>,
) -> Result<HttpResponse, StorageError> {
    let (store, path) = params.as_ref();

    let mut store_path = get_authorized_path(&authorized, store)?;
    store_path.push(path);
    if fs::metadata(&store_path).await?.is_file() {
        tracing::debug!("Deleting file {:?}", store_path);
        fs::remove_file(&store_path).await?;
    } else {
        tracing::debug!("Deleting folder {:?}", store_path);
        fs::remove_dir(&store_path).await?;
    }
    Ok(HttpResponse::Ok().finish())
}

This setup worked for this path, but would absolutely not work for another path. I inserted logs to track everything, and just found that the middleware would insert the token, but the path would just get None. How‽ I tried to slowly strip everything away from the non-functional path until it was identical to this one, but it still would not work.

Well it turns out the solution was very simple, see this:

use my_package::storage::put_storage;
use crate::storage::delete_storage;

Ah! They are imported differently. I had set up my program as both a library and a program for various reasons. However, it turns out importing the same thing from crate is different from importing it from the library. Because of the difference in import, Actix doesn't recognize that the types match, so the route can't access the attached token.

The solution is normalizing the imports. I went with going through the library for everything, because that's what rust-analyzers automatic import seems to prefer.

use my_package::storage::{put_storage, delete_storage};

Solved!