kernel: fix sexp deriving, add missing tests, canonicalize remove

Use [@@deriving sexp] with open Sexplib0.Sexp_conv instead of hand-rolling
converters (fixes non-standard Citation shape and missing field validation).
Names.t_of_sexp wraps derived version to enforce canonical sort on load.

Add tests:
- Names of_list duplicate handling
- Names sexp canonical sort guarantee (identical serialization)
- Names and Date_spec sexp roundtrips

Fix Names.remove to canonicalize output (defensive against non-canonical input).

1 files changed, 7 insertions, 17 deletions

diff --git a/lib/kernel/names.ml b/lib/kernel/names.ml
index 5f433ce..513d497 100644
--- a/lib/kernel/names.ml
+++ b/lib/kernel/names.ml
@@ -1,11 +1,13 @@
+open Sexplib0.Sexp_conv
+
 (* Celebration names by language. An open assoc list rather than a fixed record,
    so an overlay can add a language purely as data (spec §2.1). Kept sorted by
    language code so sexp output is byte-stable. *)
-type t = (Lang.t * string) list
+type t = (Lang.t * string) list [@@deriving sexp]
 
 let empty = []
 let canonical t = List.sort (fun (a, _) (b, _) -> Lang.compare a b) t
-let remove t lang = List.filter (fun (l, _) -> not (Lang.equal l lang)) t
+let remove t lang = canonical (List.filter (fun (l, _) -> not (Lang.equal l lang)) t)
 let set t lang name = canonical ((lang, name) :: remove t lang)
 let of_list l = List.fold_left (fun acc (lang, name) -> set acc lang name) empty l
 let find t lang = List.find_map (fun (l, n) -> if Lang.equal l lang then Some n else None) t
@@ -14,18 +16,6 @@ let rec find_first t = function
   | lang :: rest -> ( match find t lang with Some n -> Some n | None -> find_first t rest)
 let to_list t = t
 
-let sexp_of_t t =
-  Sexplib0.Sexp_conv.sexp_of_list (fun (lang, name) ->
-    Sexplib0.Sexp.List [ Lang.sexp_of_t lang; Sexplib0.Sexp_conv.sexp_of_string name ])
-    t
-
-let t_of_sexp sexp =
-  let list = Sexplib0.Sexp_conv.list_of_sexp (fun sexp ->
-    match sexp with
-    | Sexplib0.Sexp.List [ lang_sexp; name_sexp ] ->
-        let lang = Lang.t_of_sexp lang_sexp in
-        let name = Sexplib0.Sexp_conv.string_of_sexp name_sexp in
-        (lang, name)
-    | _ -> Sexplib0.Sexp_conv.of_sexp_error "Names.t_of_sexp: expected [lang_sexp name_sexp]" sexp)
-    sexp in
-  canonical list
+(* Wrap the derived t_of_sexp to enforce canonical sorting on load. *)
+let t_of_sexp_derived = t_of_sexp
+let t_of_sexp sexp = canonical (t_of_sexp_derived sexp)