Typed route responses

[davdroman]

First of all, thank you for putting out this amazing library along with vapor-routing. I think both are filling very important gaps in the problem space in a very elegant way.

After tour episode 4, I was keen to see how typed responses would come into play when synthesizing the API client. I was delighted to see the request part being completely type-safe in such an effortless manner, but I was also slightly disappointed to see response types weren't tied to each specific route, and were instead left to be specified by type along with the request route.

With a struct based approach, this would be fairly trivial to solve. But as I understand there are limitations in the language that make tying static types to enum cases pretty much impossible, and I reckon the exhaustivity of enums is a worthy trade-off to afford this loss of type safety vs structs.

My question is: is there any way to work around this? And even further, is there a language feature that could realistically be conceived that would allow us to solve this issue?

[lukeredpath]

My suspicion is that you don't want to tie particular responses to your routes - routing is defined as a parser/printer from (URLRequest) -> Route and back again - there isn't really any natural place for modelling the response here.

How the response is parsed is an entirely separate system and really needs a second parser/printer model of (Route) -> Response.

The problem then is that with those two functions, you can go from URLRequest -> Route -> Response and reverse but what you want to do(from a client perspective) is go from Route -> URLRequest -> Response.