Breaking: switch to new Lwt_engine.libev

Originally added in #269.

src/unix/lwt_engine.ml

@@ -175,7 +175,7 @@ external ev_io_stop : ev_loop -> ev_io -> unit = "lwt_libev_io_stop"
 external ev_timer_init : ev_loop -> float -> bool -> (unit -> unit) -> ev_timer = "lwt_libev_timer_init"
 external ev_timer_stop : ev_loop -> ev_timer -> unit  = "lwt_libev_timer_stop"
 
-class libev' ?(backend=Ev_backend.default) () = object
+class libev ?(backend=Ev_backend.default) () = object
   inherit abstract
 
   val loop = ev_init backend
@@ -203,7 +203,7 @@ class libev' ?(backend=Ev_backend.default) () = object
     lazy(ev_timer_stop loop ev)
 end
 
-class libev = libev' ()
+class libev_deprecated = libev ()
 
 (* +-----------------------------------------------------------------+
    | Select/poll based engines                                       |
@@ -418,7 +418,7 @@ end
 
 let current =
   if Lwt_config._HAVE_LIBEV && Lwt_config.libev_default then
-    ref (new libev :> t)
+    ref (new libev () :> t)
   else
     ref (new select :> t)
 
@@ -441,6 +441,6 @@ let timer_count () = !current#timer_count
 
 module Versioned =
 struct
-  class libev_1 = libev
-  class libev_2 = libev'
+  class libev_1 = libev_deprecated
+  class libev_2 = libev
 end

src/unix/lwt_engine.mli

@@ -147,7 +147,7 @@ end
 
 (** Engine based on libev. If not compiled with libev support, the
     creation of the class will raise {!Lwt_sys.Not_available}. *)
-class libev : object
+class libev : ?backend:Ev_backend.t -> unit -> object
   inherit t
 
   val loop : ev_loop
@@ -156,13 +156,6 @@ class libev : object
   method loop : ev_loop
     (** Returns [loop]. *)
 end
-[@@ocaml.deprecated
-" This class will soon have parameters for selecting a libev backend. This will
- be a breaking change in Lwt 3.0.0. See
-   https://github.com/ocsigen/lwt/pull/269
- To preserve the current signature, use Lwt_engine.Versioned.libev_1
- To use the replacement immediately, use Lwt_engine.Versioned.libev_2 ()
- Both alternatives require Lwt >= 2.7.0."]
 
 (** Engine based on [Unix.select]. *)
 class select : t
@@ -223,15 +216,23 @@ sig
     method loop : ev_loop
   end
   [@@ocaml.deprecated
-   "Deprecated in favor of Lwt_engine.Versioned.libev_2. See
+" Deprecated in favor of Lwt_engine.libev. See
   https://github.com/ocsigen/lwt/pull/269"]
-  (** @deprecated In favor of {!libev_2}.
+  (** Old version of {!Lwt_engine.libev}. The current {!Lwt_engine.libev} allows
+      selecting the libev back end.
+
+      @deprecated Use {!Lwt_engine.libev}.
       @since 2.7.0 *)
 
-  (** @since 2.7.0 *)
   class libev_2 : ?backend:Ev_backend.t -> unit -> object
     inherit t
     val loop : ev_loop
     method loop : ev_loop
   end
+  [@@ocaml.deprecated
+" In Lwt >= 3.0.0, this is an alias for Lwt_engine.libev."]
+  (** Since Lwt 3.0.0, this is just an alias for {!Lwt_engine.libev}.
+
+      @deprecated Use {!Lwt_engine.libev}.
+      @since 2.7.0 *)
 end