cohttp-async: base/async v0.16 compatibility

[dkalinichenko-js]

The next major release of Base will rename the Caml module to Stdlib. The next major release of Async will make the how argument mandatory for certain Deferred operations. This PR updates cohttp-async before releasing these changes, since some Jane Street packages depend on it.

I'm not sure about the testing story for this change. The preview versions of our libraries are accessible at our bleeding edge repo (https://github.com/janestreet/opam-repository), and currently only work with OCaml 4.14.1. We are working towards 5.0.0 compatibility, but do not want it to delay the renaming and API tweaks.

[mseri]

Thanks. As soon as base/async libraries are released I will test the changes, merge them and make a release. Anybody that uses the dev versions can pin the branch of this PR and use them in the meantime.

[avsm]

Hang on, I don't think this should be merged until the Base v0.16 release has been cut and submitted. Otherwise, cohttp-async will be uninstallable in the opam-repository, and not suitable for merging there.

@dkalinichenko-js -- what's the rough timeline for v0.16 being publicly released (even as a preview RC?).

[dkalinichenko-js]

Hang on, I don't think this should be merged until the Base v0.16 release has been cut and submitted. Otherwise, cohttp-async will be uninstallable in the opam-repository, and not suitable for merging there.

@dkalinichenko-js -- what's the rough timeline for v0.16 being publicly released (even as a preview RC?).

Will it actually be uninstallable, or just install the previous version of cohttp-async? I thought it would resolve the dependency to use base v0.15, but maybe I'm wrong.

Rough timeline is late March-early April.

[mseri]

Hang on, I don't think this should be merged until the Base v0.16 release has been cut and submitted.

That is exactly my suggestion, to leave it open until the upstream release happen

[avsm]

Sorry @mseri, I entirely misread your message! Quite right.

@d-kalinichenko if this were released onto stable opam-repo, then the cohttp-async package would be uninstallable since there would be no v0.16 base packages (without adding the bleeding edge remote). The easiest way to test the package along with your release is for you to clone the cohttp opam files over to the Jane Street bleeding-edge repository, so they're all included there in a batch.

This is all a little more painful than we would like since you also have to drag along all the other (non-cohttp-async) packages in this repository for the versioning to work out. Easiest just to coordinate with us as you do the v0.16 release and we can release things all at roughly the same time.

[mseri]

This PR needs more work, not just to fix the CI, but it seems that also some tests need fixing:

File "cohttp-async/test/test_async_integration.ml", lines 83-87, characters 8-56:
83 | ........resps
84 |         |> Deferred.List.iter ~f:(fun (_resp, body) ->
85 |                let expected_body = body_q |> Queue.dequeue_exn in
86 |                body |> Body.to_string >>| fun body ->
87 |                assert_equal ~printer expected_body body)
Error (warning 5 [ignored-partial-application]): this function application is partial,
maybe some arguments are missing.
File "cohttp-async/test/test_async_integration.ml", lines 83-87, characters 8-56:
83 | ........resps
84 |         |> Deferred.List.iter ~f:(fun (_resp, body) ->
85 |                let expected_body = body_q |> Queue.dequeue_exn in
86 |                body |> Body.to_string >>| fun body ->
87 |                assert_equal ~printer expected_body body)
Error: This expression has type
         how:Async_kernel.Monad_sequence.how -> unit io
       but an expression was expected of type 'a io