How to share axum routes between server and lambda?

[tmpfs]

Hi,

I am trying to share routes between a lambda with a normal axum server so that I can run a local server for development and integration testing and deploy as a lambda (which is proxied via API Gateway). This means the router needs to work with both axum::body::Body and lambda_http::Body.

So I defined a generic function that declares the routes with this signature:

    pub fn service<B>() -> Router<(), B> where
        B: HttpBody + Send + 'static,
        <B as HttpBody>::Data: Send,
        <B as HttpBody>::Error: Send + Sync + std::error::Error + 'static
    {
    Router::new() // all the service routes
    }

Which works fine for a normal axum server using axum::body::Body (note I cannot remove the std::error::Error trait bound as it is required for axum routing).

However when I invoke the service() function from the code that calls lambda_http::run to set up the routes I get this compiler error:

   |
66 |     let v1 = server::Server::service();
   |              ^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
   = help: the trait `Sized` is not implemented for `(dyn std::error::Error + Send + Sync + 'static)`
   = help: the following other types implement trait `std::error::Error`:
             Box<(dyn sqlx_core::error::DatabaseError + 'static)>
             Box<T>
   = note: required for `Box<(dyn std::error::Error + Send + Sync + 'static)>` to implement `std::error::Error`
note: required by a bound in `sos_platform::server::Server::service`
  --> /Users/muji/git/sos/platform/src/server.rs:76:47
   |
76 |         <B as HttpBody>::Error: Send + Sync + std::error::Error + 'static
   |                                               ^^^^^^^^^^^^^^^^^ required by this bound in `Server::service`

For more information about this error, try `rustc --explain E0277`.

Which appears to be because the HttpBody implementation in lambda_events uses an associated type Error which is defined as:

pub type Error = Box<dyn std::error::Error + Send + Sync>;

I think to fix this HttpBody::Error would need to be a concrete type rather then a type alias so it implements Sized. Is that correct?

At the moment I can workaround this by duplicating my routes in the lambda but that's very far from ideal.