Commits on Apr 4, 2024

1. cohttp-eio: client: use permissive argument type for make_generic …

   Currently, Cohttp_eio.Client.make_generic takes a function that returns a value
   of type `_ Eio.Net.stream_socket` as an argument. This type is too strict and
   can be relaxed to `_ Eio.Flow.two_way`. The difference between these two
   types is actually important when we use cohttp-eio with ocaml-tls. Consider the
   following code:
   
   ```
   let authenticator = Ca_certs.authenticator () |> Result.get_ok
   
   let connect_via_tls url socket =
     let tls_config = Tls.Config.client ~authenticator () in
     let host =
       Uri.host url
       |> Option.map (fun x -> Domain_name.(host_exn (of_string_exn x)))
     in
     Tls_eio.client_of_flow ?host tls_config socket
   
   let connect net ~sw url =
     (* NOTE: Do something different than `Cohttp_eio.Client.tcp_address` here and get `addr` *)
     let socket = Eio.Net.connect ~sw net addr in
     connect_via_tls url socket
   
   let () =
     Eio_main.run @@ fun env ->
     Cohttp_eio.Client.make_generic (fun ~sw url ->
         let flow = connect (Eio.Stdenv.net env) ~sw url in
         flow (* <<---- TYPE ERROR HERE!
   
   Error: This expression has type
            Tls_eio.t = [ `Flow | `R | `Shutdown | `Tls | `W ] Eio_unix.source
          but an expression was expected of type
            [> [> `Generic ] Eio.Net.stream_socket_ty ] Eio_unix.source
          Type [ `Flow | `R | `Shutdown | `Tls | `W ] is not compatible with type
            [> ([> `Generic ] as 'a) Eio.Net.stream_socket_ty ] =
              [> `Close
               | `Flow
               | `Platform of 'a
               | `R
               | `Shutdown
               | `Socket
               | `Stream
               | `W ]
          The first variant type does not allow tag(s)
          `Close, `Platform, `Socket, `Stream
   *))
   ```
   
   This code won't compile if `make_generic` expects `_ Eio.Net.stream_socket`,
   but it will compile if `_ Eio.Flow.two_way`.
   
   This patch solves the above problem by changing the interface of `make_generic`
   to `(sw:Switch.t -> Uri.t -> _ Eio.Flow.two_way) -> t`. The implementation
   of `make_generic` is effectively an identity function, so we don't need to
   change the implementation.

   

   ushitora-anqou committed Apr 4, 2024
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