multipart_form ~identify req body returns a fiber which parses the given body and a stream of each part of the given body. The goal is to propose an easier interface specially for CoHTTP. By this way, this function expects a CoHTTP request and a CoHTTP body.

To consume the returned stream, the returned fiber must be launched:

  let consume_parts stream =
    let* part = Lwt_stream.get stream in
    match part with
    | None -> ...
    | Some (uid, headers, body) -> ...

  let handler _ req body =
    let `Tree th, stream = Multipart_form_cohttp.Server.multipart_form
      ~identify req body in
    Lwt.catch begin fun () ->
      let* tree, _ = Lwt.both (th, consume_parts stream) in
      ...
    end @@ function
    | Invalid_multipart_form err -> ...

In this example, we use Lwt.both to concurrently parse and consume parts. If the body is not a valid multipart-form/data, the exception Invalid_multipart_form is raised.