CA-352073: Prepare to reuse defaults unmarshalling code

This will allow this code to generate a binding not only for the value
with the unmarshalled value, but for the rpc value as well. This is
needed to be able to explicitely define the parameter list with the
default values embedded into the rbac check

Signed-off-by: Pau Ruiz Safont <pau.safont@citrix.com>

ocaml/idl/ocaml_backend/gen_server.ml

@@ -111,9 +111,8 @@ let operation (obj : obj) (x : message) =
     else
       List.map O.string_of_param args_without_default_values
   in
-  let string_args =
-    List.map (fun s -> Printf.sprintf "%s_rpc" s) orig_string_args
-  in
+  let to_rpc_name s = Printf.sprintf "%s_rpc" s in
+  let string_args = List.map to_rpc_name orig_string_args in
   let is_non_constructor_with_defaults =
     (not is_ctor) && has_default_args x.DT.msg_params
   in
@@ -194,6 +193,26 @@ let operation (obj : obj) (x : message) =
     else
       List.exists (fun a -> is_session_arg a) args_without_default_values
   in
+  let unmarshall_default_params =
+    List.mapi
+      (fun param_count default_param ->
+        let param_name = OU.ocaml_of_record_name default_param.DT.param_name in
+        let param_type = OU.alias_of_ty default_param.DT.param_type in
+        let try_and_get_default =
+          Printf.sprintf "List.nth default_args %d" param_count
+        in
+        let default_value =
+          match default_param.DT.param_default with
+          | None ->
+              "** EXPECTED DEFAULT VALUE IN THIS PARAM **"
+          | Some default ->
+              Datamodel_values.to_ocaml_string default
+        in
+        Printf.sprintf "let %s = %s_of_rpc (try %s with _ -> %s) in" param_name
+          param_type try_and_get_default default_value
+      )
+      msg_params_with_default_values
+  in
   let rbac_check_begin =
     if has_session_arg then
       let serialize_list lst =
@@ -236,26 +255,7 @@ let operation (obj : obj) (x : message) =
         args_without_default_values
     )
     (* and for every default value we try to get this from default_args or default it *)
-    @ List.mapi
-        (fun param_count default_param ->
-          let param_name =
-            OU.ocaml_of_record_name default_param.DT.param_name
-          in
-          let param_type = OU.alias_of_ty default_param.DT.param_type in
-          let try_and_get_default =
-            Printf.sprintf "List.nth default_args %d" param_count
-          in
-          let default_value =
-            match default_param.DT.param_default with
-            | None ->
-                "** EXPECTED DEFAULT VALUE IN THIS PARAM **"
-            | Some default ->
-                Datamodel_values.to_ocaml_string default
-          in
-          Printf.sprintf "let %s = %s_of_rpc (try %s with _ -> %s) in"
-            param_name param_type try_and_get_default default_value
-        )
-        msg_params_with_default_values
+    @ unmarshall_default_params
   in
   let may_be_side_effecting msg =
     match msg.msg_tag with