ocaml: use new List.head instead of List.nth_opt

The return type is the same, but it's more obvious to see what it does

Signed-off-by: Pau Ruiz Safont <[email protected]>

Author: psafont

dune-project

@@ -361,6 +361,7 @@
   ; because it is not in xs-opam yet
   rrd-transport
   rrdd-plugin
+  xapi-stdext-std
   xapi-tracing-export
   xen-api-client
   (alcotest :with-test)

ocaml/database/db_connections.ml

@@ -55,7 +55,7 @@ let choose connections =
       Some most_recent
 
 let preferred_write_db () =
-  List.nth_opt (Db_conn_store.read_db_connections ()) 0
+  Xapi_stdext_std.Listext.List.head (Db_conn_store.read_db_connections ())
 
 (* !!! FIX ME *)
 

ocaml/libs/pciutil/dune

@@ -4,6 +4,7 @@
   (libraries
     threads
     unix
+    xapi-stdext-std
     xapi-stdext-unix
   )
 )

ocaml/libs/pciutil/pciutil.ml

@@ -65,7 +65,7 @@ let parse vendor device =
   access_list
     ["/usr/share/hwdata/pci.ids"; "/usr/share/misc/pci.ids"]
     [Unix.R_OK]
-  |> Fun.flip List.nth_opt 0
+  |> Xapi_stdext_std.Listext.List.head
   |> Option.map (fun path -> parse_from path vendor device)
   |> function
   | Some vd ->

ocaml/xapi-aux/dune

@@ -16,6 +16,7 @@
     xapi-idl.network
     xapi-inventory
     xapi-log
+    xapi-stdext-std
     xapi-stdext-threads
     xapi-stdext-unix
     xml-light2

ocaml/xapi-aux/networking_info.ml

@@ -15,6 +15,8 @@ module Net = Network_client.Client
 
 module L = Debug.Make (struct let name = __MODULE__ end)
 
+module Listext = Xapi_stdext_std.Listext.List
+
 let get_hostname () = try Unix.gethostname () with _ -> ""
 
 type management_ip_error =
@@ -99,7 +101,7 @@ let get_management_ip_addrs ~dbg =
 let get_management_ip_addr ~dbg =
   match get_management_ip_addrs ~dbg with
   | Ok (preferred, _) ->
-      List.nth_opt preferred 0 |> Option.map Ipaddr.to_string
+      Listext.head preferred |> Option.map Ipaddr.to_string
   | Error _ ->
       None
 
@@ -113,7 +115,7 @@ let get_host_certificate_subjects ~dbg =
         let ips = List.(rev_append (rev preferred) others) in
         Option.fold ~none:(Error IP_missing)
           ~some:(fun ip -> Ok (List.map ipaddr_to_octets ips, ip))
-          (List.nth_opt ips 0)
+          (Listext.head ips)
   in
   let dns_names = dns_names () in
   let name =

ocaml/xapi/import.ml

@@ -439,9 +439,8 @@ module VM : HandlerTools = struct
     in
 
     let maybe_template =
-      List.nth_opt
+      Listext.List.head
         (Db.VM.get_by_name_label ~__context ~label:vm_record.API.vM_name_label)
-        0
     in
     match (is_default_template, maybe_template) with
     | true, Some template ->

ocaml/xapi/xapi_pif_helpers.ml

@@ -273,7 +273,7 @@ let get_primary_address ~__context ~pif =
     match Db.PIF.get_IP ~__context ~self:pif with "" -> None | ip -> Some ip
   )
   | `IPv6 ->
-      List.nth_opt (get_non_link_ipv6 ~__context ~pif) 0
+      Xapi_stdext_std.Listext.List.head (get_non_link_ipv6 ~__context ~pif)
 
 let get_pif_position ~__context ~pif_rec =
   let n_of_xenbrn_opt bridge =

ocaml/xapi/xapi_sm.ml

@@ -78,17 +78,18 @@ let addto_pending_hosts_features ~__context self new_features =
     curr_pending_features
 
 let valid_hosts_pending_features ~__context pending_features =
-  if List.length pending_features <> List.length (Db.Host.get_all ~__context)
-  then (
-    debug "%s: Not enough hosts have registered their sm features" __FUNCTION__ ;
-    []
-  ) else
-    List.map snd pending_features |> fun l ->
-    List.fold_left Smint.Feature.compat_features
-      (* The list in theory cannot be empty due to the if condition check, but do
-         this just in case *)
-      (List.nth_opt l 0 |> Option.fold ~none:[] ~some:Fun.id)
-      (List.tl l)
+  let __FUN = __FUNCTION__ in
+  let not_enough_msg () =
+    debug "%s: Not enough hosts have registered their sm features" __FUN
+  in
+  match pending_features with
+  | [] ->
+      not_enough_msg () ; []
+  | features
+    when List.compare_lengths features (Db.Host.get_all ~__context) <> 0 ->
+      not_enough_msg () ; []
+  | (_, x) :: xs ->
+      List.fold_left Smint.Feature.compat_features x (List.map snd xs)
 
 let remove_valid_features_from_pending ~__context ~self valid_features =
   let valid_features = List.map Smint.Feature.unparse valid_features in

ocaml/xapi/xapi_vdi.ml

@@ -886,28 +886,14 @@ let wait_for_vbds_to_be_unplugged_and_destroyed ~__context ~self ~timeout =
   let classes = [Printf.sprintf "VDI/%s" (Ref.string_of self)] in
   let next_token_and_vbds ~token ~timeout =
     let most_recent_vbds_field events =
-      (* We do not assume anything here about the order of the list of events we get. *)
-      let most_recent_snapshot =
-        let events_from_newest_to_oldest =
-          (* We need to sort the timestamp strings in decreasing order *)
-          List.sort
-            (fun e1 e2 -> Event_types.(-String.compare e1.ts e2.ts))
-            events
-        in
-        let snapshots_from_newest_to_oldest =
-          (* filter_map preserves the order of elements *)
-          List.filter_map
-            (fun event -> event.Event_types.snapshot)
-            events_from_newest_to_oldest
-        in
-        List.nth_opt snapshots_from_newest_to_oldest 0
-      in
-      Option.map
-        (fun snapshot ->
-          let vdi = API.vDI_t_of_rpc snapshot in
-          vdi.API.vDI_VBDs
-        )
-        most_recent_snapshot
+      (* We need to sort the timestamp strings in decreasing order *)
+      List.sort (fun e1 e2 -> Event_types.(-String.compare e1.ts e2.ts)) events
+      |> List.filter_map (fun event -> event.Event_types.snapshot)
+      |> Xapi_stdext_std.Listext.List.head
+      |> Option.map (fun snapshot ->
+             let vdi = API.vDI_t_of_rpc snapshot in
+             vdi.API.vDI_VBDs
+         )
     in
     let from =
       let timeout = Scheduler.span_to_s timeout in