RouterIntoService not Clone?

[bryanburgers]

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

Bug Report

Version

• axum 0.7

Description

I'm trying to turn a Router into a Service so I can use it in root_router.nest_service(...).

• Router has a .into_service() method
• Router::nest_service requires the service to implement Clone
• Router does implement Clone.
• RouterIntoService does not implement Clone.

All of that together means that, while I can write code that does

let sub_router = submod::create_router();

let router = Router::new()
  .nest("/sub", sub_router);

I can not write code that does

let sub_router_service = submod::create_router().into_service();

let router = Router::new()
  .nest_service("/sub", sub_router_service);

This seems like it might be an oversight? It looks to me like RouterIntoService should trivially implement Clone? (It only has a Router in it.)

---

Why do I want to use .nest_service instead of .nest in the first place? It's because I have a layer on my subrouter, and when I use .nest that layer doesn't get called for non-matching routes.

[davidpdrsn]

Sure, implementing Clone for RouterIntoService seems fine but I'm confused as to why you can't just use Router::nest, since you already have a Router.

[bryanburgers]

why you can't just use Router::nest, since you already have a Router.

The use case here is that in my sub-router, I'm using sub_router.layer(...) to add a non-trivial URL interceptor that handles requests in a particular way. I want that layer to run for all unhandled routes within that sub_router.

If I nest the sub_router directly into the router, the sub_router doesn't intercept those requests. If I nest the sub_router as a service, the sub_router does intercept those requests.

More details: I have to implement a sub-set of https://www.odata.org/ for part of my API. OData does some weird stuff with URLs that doesn't map directly or nicely to using a Router. So I have my own component called odata_router::Router that implements the subset of OData I need.

It looks like we discussed this at #1245. And some code that I wrote at the time to demonstrate something close to what I'm trying to do is here: https://github.com/bryanburgers/axum-nest-repro.

My actual code looks like this:

// odata.rs
pub fn create_router(state: ApiContext) -> Router {
    // Custom component for doing OData routing
    let odata_router = odata_router::Router::new(state.clone())
        // GET /odata/Property('thisistheid')
        .get("Property", get_property)
        // GET /odata/Property?$top=200$filter=...
        .list("Property", list_property)
        // GET /odata/OpenHouse('thisistheid')
        .get("OpenHouse", get_openhouse)
        // GET /odata/OpenHouse?$top=200$filter=...
        .list("OpenHouse", list_openhouse);

    // axum Router
    Router::new()
        // basic route
        .route("/$metadata", get(edmx::get_metadata))
        // handle everything else that we can with the custom router
        .layer(odata_router)
        .with_state(state)
}

async fn get_property(
    odata_router::Id(id): odata_router::Id,
    ReplicationToken(_token): ReplicationToken,
    State(context): State<ApiContext>,
) -> Result<Json<MaskedProperty>, Error> {
    // ...
}

// lib.rs
    let odata_service = reso::create_router(context.clone()).into_service();
    let api_router = api::create_router();

    Router::new()
        .nest("/api", api_router)
        .nest_service("/odata", odata_service)
        .with_state(context)