[server] check fields declaration for name validity

src/plugins/server/data.ml

@@ -332,9 +332,18 @@ struct
     if s.published then
       raise (Invalid_argument "Server.Data.Record: already published")
 
+  let is_valid_field_name s name =
+    if List.exists (fun f -> String.equal f.Package.fd_name name) s.fields then
+      raise (Invalid_argument ("Server.Data.Record: a field with name '" ^ name
+                               ^ "' already exists")) ;
+    if not (Str.string_match (Str.regexp "[a-zA-Z0-9 _-]+$") name 0) then
+      raise (Invalid_argument ("Server.Data.Record: field names must not be \
+                                exotic ('" ^ name ^ "')"))
+
   let field (type a r) (s : r signature)
       ~name ~descr ?default (d : a data) : (r,a) field =
     not_published s ;
+    is_valid_field_name s name ;
     let module D = (val d) in
     begin match default with
       | None -> ()
@@ -354,6 +363,7 @@ struct
   let option (type a r) (s : r signature)
       ~name ~descr (d : a data) : (r,a option) field =
     not_published s ;
+    is_valid_field_name s name ;
     let module D = (val d) in
     let field = Package.{
         fd_name = name ;