common/mltools: xpath_helpers: Get rid of xpath_*_default functions.

Instead of using ‘xpath_(string|int|int64)_default’ we can write the
equivalent code using ‘Option.default’.  This is not quite so concise,
but may be easier to understand.

eg:
  xpath_int_default xctx "xpath_expr" 10
->
  Option.default 10 (xpath_int xctx "xpath_expr")

common/mltools/xpath_helpers.ml

@@ -40,15 +40,3 @@ let xpath_eval parsefn xpathctx expr =
 let xpath_string = xpath_eval identity
 let xpath_int = xpath_eval int_of_string
 let xpath_int64 = xpath_eval Int64.of_string
-
-(* Parse an xpath expression and return a string/int; if the expression
- * doesn't match, return the default.
- *)
-let xpath_eval_default parsefn xpath expr default =
-  match xpath_eval parsefn xpath expr with
-  | None -> default
-  | Some s -> s
-
-let xpath_string_default = xpath_eval_default identity
-let xpath_int_default = xpath_eval_default int_of_string
-let xpath_int64_default = xpath_eval_default Int64.of_string

common/mltools/xpath_helpers.mli

@@ -25,9 +25,3 @@ val xpath_int : Xml.xpathctx -> string -> int option
 val xpath_int64 : Xml.xpathctx -> string -> int64 option
 (** Parse an xpath expression and return a string/int.  Returns
     [Some v], or [None] if the expression doesn't match. *)
-
-val xpath_string_default : Xml.xpathctx -> string -> string -> string
-val xpath_int_default : Xml.xpathctx -> string -> int -> int
-val xpath_int64_default : Xml.xpathctx -> string -> int64 -> int64
-(** Parse an xpath expression and return a string/int; if the expression
-    doesn't match, return the default. *)

v2v/copy_to_local.ml

@@ -243,14 +243,14 @@ and parse_libvirt_xml guest_name xml =
   let xpathctx = Xml.xpath_new_context doc in
   Xml.xpath_register_ns xpathctx
                         "vmware" "http://libvirt.org/schemas/domain/vmware/1.0";
-  let xpath_string = xpath_string xpathctx
-  and xpath_string_default = xpath_string_default xpathctx in
+  let xpath_string = xpath_string xpathctx in
 
   (* Get the dcpath, only present for libvirt >= 1.2.20 so use a
    * sensible default for older versions.
    *)
   let dcpath =
-    xpath_string_default "/domain/vmware:datacenterpath" "ha-datacenter" in
+    Option.default "ha-datacenter"
+                   (xpath_string "/domain/vmware:datacenterpath") in
 
   (* Parse the disks. *)
   let get_disks, add_disk =

v2v/parse_libvirt_xml.ml

@@ -77,10 +77,8 @@ let parse_libvirt_xml ?conn xml =
   let doc = Xml.parse_memory xml in
   let xpathctx = Xml.xpath_new_context doc in
   let xpath_string = xpath_string xpathctx
-  and xpath_string_default = xpath_string_default xpathctx
   and xpath_int = xpath_int xpathctx
-  (*and xpath_int_default = xpath_int_default xpathctx*)
-  and xpath_int64_default = xpath_int64_default xpathctx in
+  and xpath_int64 = xpath_int64 xpathctx in
 
   let hypervisor =
     match xpath_string "/domain/@type" with
@@ -92,7 +90,8 @@ let parse_libvirt_xml ?conn xml =
     | None | Some "" ->
        error (f_"in the libvirt XML metadata, <name> is missing or empty")
     | Some s -> s in
-  let memory = xpath_int64_default "/domain/memory/text()" (1024L *^ 1024L) in
+  let memory =
+    Option.default (1024L *^ 1024L) (xpath_int64 "/domain/memory/text()") in
   let memory = memory *^ 1024L in
 
   let cpu_vendor = xpath_string "/domain/cpu/vendor/text()" in
@@ -317,7 +316,7 @@ let parse_libvirt_xml ?conn xml =
            (* This is for testing curl, eg for testing VMware conversions
             * without needing VMware around.
             *)
-           let path = xpath_string_default "source/@name" "" in
+           let path = Option.default "" (xpath_string "source/@name") in
            let qemu_uri = create_curl_qemu_uri driver host port path in
            add_disk qemu_uri format controller P_dont_rewrite
         | Some protocol, _, _ ->

v2v/parse_ovf_from_ova.ml

@@ -52,9 +52,7 @@ let parse_ovf_from_ova ovf_filename =
 
   let xpath_string = xpath_string xpathctx
   and xpath_int = xpath_int xpathctx
-  and xpath_string_default = xpath_string_default xpathctx
-  and xpath_int_default = xpath_int_default xpathctx
-  and xpath_int64_default = xpath_int64_default xpathctx in
+  and xpath_int64 = xpath_int64 xpathctx in
 
   let rec parse_top () =
     (* Search for vm name. *)
@@ -64,11 +62,11 @@ let parse_ovf_from_ova ovf_filename =
       | Some _ as name -> name in
 
     (* Search for memory. *)
-    let memory = xpath_int64_default "/ovf:Envelope/ovf:VirtualSystem/ovf:VirtualHardwareSection/ovf:Item[rasd:ResourceType/text()=4]/rasd:VirtualQuantity/text()" (1024L *^ 1024L) in
+    let memory = Option.default (1024L *^ 1024L) (xpath_int64 "/ovf:Envelope/ovf:VirtualSystem/ovf:VirtualHardwareSection/ovf:Item[rasd:ResourceType/text()=4]/rasd:VirtualQuantity/text()") in
     let memory = memory *^ 1024L *^ 1024L in
 
     (* Search for number of vCPUs. *)
-    let vcpu = xpath_int_default "/ovf:Envelope/ovf:VirtualSystem/ovf:VirtualHardwareSection/ovf:Item[rasd:ResourceType/text()=3]/rasd:VirtualQuantity/text()" 1 in
+    let vcpu = Option.default 1 (xpath_int "/ovf:Envelope/ovf:VirtualSystem/ovf:VirtualHardwareSection/ovf:Item[rasd:ResourceType/text()=3]/rasd:VirtualQuantity/text()") in
 
     (* CPU topology.  coresPerSocket is a VMware proprietary extension.
      * I couldn't find out how hyperthreads is specified in the OVF.
@@ -91,7 +89,7 @@ let parse_ovf_from_ova ovf_filename =
            Some sockets, Some cores_per_socket in
 
     (* BIOS or EFI firmware? *)
-    let firmware = xpath_string_default "/ovf:Envelope/ovf:VirtualSystem/ovf:VirtualHardwareSection/vmw:Config[@vmw:key=\"firmware\"]/@vmw:value" "bios" in
+    let firmware = Option.default "bios" (xpath_string "/ovf:Envelope/ovf:VirtualSystem/ovf:VirtualHardwareSection/vmw:Config[@vmw:key=\"firmware\"]/@vmw:value") in
     let firmware =
       match firmware with
       | "bios" -> BIOS
@@ -141,7 +139,8 @@ let parse_ovf_from_ova ovf_filename =
         | Some id -> parent_controller id in
 
       Xml.xpathctx_set_current_context xpathctx n;
-      let file_id = xpath_string_default "rasd:HostResource/text()" "" in
+      let file_id =
+        Option.default "" (xpath_string "rasd:HostResource/text()") in
       let rex = PCRE.compile "^(?:ovf:)?/disk/(.*)" in
       if PCRE.matches rex file_id then (
         (* Chase the references through to the actual file name. *)
@@ -231,7 +230,8 @@ let parse_ovf_from_ova ovf_filename =
       let n = Xml.xpathobj_node obj i in
       Xml.xpathctx_set_current_context xpathctx n;
       let vnet =
-        xpath_string_default "rasd:ElementName/text()" (sprintf"eth%d" i) in
+        Option.default (sprintf"eth%d" i)
+                       (xpath_string "rasd:ElementName/text()") in
       let nic = {
         s_mac = None;
         s_nic_model = None;