[Libguestfs] [PATCH v2v 1/3] lib/utils.ml: Make with_nbd_connect_unix meta_contexts erasable

[Richard W.M. Jones]

Make the meta_contexts parameter of Utils.with_nbd_connect_unix
optional and erasable.  This involves three connected changes, we
first make it optional (ie. '?meta_contexts'), providing the obvious
default of empty list.  We then need to move it to the first parameter
so OCaml can erase it even if we partially apply this function.
Finally remove the label from the function parameter 'f'.

I'm not quite sure why the last change is necessary, but OCaml cannot
erase ?meta_contexts without it, and in any case it's not necessary to
label this parameter as it doesn't add any extra type safety and you
wouldn't want callers to swap over the socket and function parameter
because that would make calling code less clear.  (The same applies to
~socket but I didn't change that).
---
 lib/utils.ml  | 4 ++--
 lib/utils.mli | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/utils.ml b/lib/utils.ml
index d6861d0889..863cfc4eb0 100644
--- a/lib/utils.ml
+++ b/lib/utils.ml
@@ -165,7 +165,7 @@ let rec wait_for_file filename timeout =
 
 let metaversion = Digest.to_hex (Digest.string Config.package_version_full)
 
-let with_nbd_connect_unix ~socket ~meta_contexts ~f =
+let with_nbd_connect_unix ?(meta_contexts = []) ~socket f =
   let nbd = NBD.create () in
   protect
     ~f:(fun () ->
@@ -181,7 +181,7 @@ let get_disk_allocated ~dir ~disknr =
   let socket = sprintf "%s/out%d" dir disknr
   and alloc_ctx = "base:allocation" in
   with_nbd_connect_unix ~socket ~meta_contexts:[alloc_ctx]
-    ~f:(fun nbd ->
+    (fun nbd ->
          if NBD.can_meta_context nbd alloc_ctx then (
            (* Get the list of extents, using a 2GiB chunk size as hint. *)
            let size = NBD.get_size nbd
diff --git a/lib/utils.mli b/lib/utils.mli
index 3096eb1466..76a2ec8c40 100644
--- a/lib/utils.mli
+++ b/lib/utils.mli
@@ -78,9 +78,9 @@ val metaversion : string
     Eventually we may switch to using an "open metadata" format instead
     (eg. XML). *)
 
-val with_nbd_connect_unix : socket:string ->
-                            meta_contexts:string list ->
-                            f:(NBD.t -> 'a) ->
+val with_nbd_connect_unix : ?meta_contexts:string list ->
+                            socket:string ->
+                            (NBD.t -> 'a) ->
                             'a
 (** [with_nbd_connect_unix socket meta_contexts f] calls function [f] with the
     NBD server at Unix domain socket [socket] connected, and the metadata
-- 
2.32.0