impl Endpoint for Service, for service nesting

[tirr-c]

This is a half-baked version of nesting. Need to strip the path prefix, but I feel this is a good first step! Nevermind, I managed to write necessary mechanics for nesting.

• HttpService impl is refactored to use Endpoint impl internally.
• Added Route::strip_prefix. When used, this will strip the route path prefix from request before passing it to the endpoint.

With this PR, we can finally nest Tide services!

let mut inner = tide::new();
inner.at("/").get(|_| async { "root" });
inner.at("/foo").get(|_| async { "foo" });
inner.at("/bar").get(|_| async { "bar" });

let mut outer = tide::new();
outer
    .at("/nested")
    .strip_prefix() // catch /nested and /nested/*
    .get(inner.into_http_service()); // the prefix /nested will be stripped here

Might need a better name for strip_prefix, like prefixed?

[eignnx]

I wonder if something like nested_service would be clearer than strip_prefix?

[yoshuawuyts]

This patch looks good! I think we can probably merge it as-is.

Looking Ahead

I'm curious if we could move forward from here though. Ideally folks could write something like this, and it would just work:

let mut inner = tide::new();
inner.at("/").get(|_| async { "root" });
inner.at("/foo").get(|_| async { "foo" });
inner.at("/bar").get(|_| async { "bar" });

let mut outer = tide::new();
outer.at("/nested").get(inner);

But we'd need to implement two changes for this:

• Either implement HttpService for Server, or introduce a new trait: IntoHttpService that knows how to convert something into an http service. It'd be neat if we could remove the Server / Service distinction.
• Make it so we can discern between Server and regular Endpoints without needing to toggle methods manually. Maybe we could add this as a method on Endpoint that is called once when passed into a handler.

I think if we put those together, nesting services will become something that will become incredibly intuitive!

[yoshuawuyts]

@tirr-c oh, also another question: on Discord someone asked whether we supported middleware on sub-routes, and you mentioned this patch would add support for that. So it looks like this patch specifically doesn't add a middleware method on Route; but it does seem like that would be possible to add as a follow-up?

[tirr-c]

@yoshuawuyts I think this is good to merge now! Marked strip_prefix as unstable, as its name might change in the near future.

And yeah, per-route middleware shouldn't be hard to implement. I'll add it as a follow-up.