axum: allow body types other than axum::body::Body in Services passed to serve
#3205
+61
−19
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yanns
reviewed
Feb 3, 2025
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| let app = ServiceBuilder::new() | ||
| .layer_fn(|_| tower::service_fn(|_| std::future::ready(Ok(Response::new(CustomBody))))) | ||
| .service(Router::<()>::new()); |
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If we add some routes, which type will be the body? The axum body type? Or CustomBody?
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CustomBody. The layer returns a service which always returns that without even using the Router in this test.
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Could we add an handle to check if this works? Or are our handlers tight to our body implementation?
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I can do that (in a few days).
The handler (and Router) would still return axum::body::Body, it's just the outer layer which changes that to something else.
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This is not reverting anything from #1751. That was about the router being generic over the body. |
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Motivation
A user in #3202 tried to use middlewares around the whole
Routerso that their layers run before routing happens. They ran into problems caused by their layers changing theBodytype.So far I've seen only the
NormalizePathLayerused in this way which does not change theBodytype so there were never issues. But I don't see a reason not to support this for other layers that do change the body, such asCompressionLayer.Solution
This PR adds another generic parameter to
Serveto keep track of theResponse::Bodytype returned by the service provided.There are no breaking changes as far as I can tell as inference knows the body type. This could break someone who for some reason names the type parameters explicitly. There is no rush with this and we may want to wait with this and release it in the next breaking release.
Alternatives
We may also choose not to support this. Users can just map the response body with
.map_response_body(axum::body::Body::new)before callignserve. The price is just one box (and maybe a bit of ergonomics) as far as I can tell.