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).

6 files changed, 13 insertions, 74 deletions

diff --git a/lib/kernel/citation.ml b/lib/kernel/citation.ml
index a819040..4485958 100644
--- a/lib/kernel/citation.ml
+++ b/lib/kernel/citation.ml
@@ -1,3 +1,5 @@
+open Sexplib0.Sexp_conv
+
 (* Scripture references only -- never scripture text (spec §1: that is lectio's
    job). *)
 type part = First | Psalm | Second | Gospel | Tract | Alleluia | Sequence
@@ -14,20 +16,4 @@ let part_of_string = function
   | "gospel" -> Some Gospel | "tract" -> Some Tract | "alleluia" -> Some Alleluia
   | "sequence" -> Some Sequence | _ -> None
 
-type t = { part : part; reference : string }
-
-let sexp_of_t { part; reference } =
-  Sexplib0.Sexp.List [
-    Sexplib0.Sexp_conv.sexp_of_string "part";
-    sexp_of_part part;
-    Sexplib0.Sexp_conv.sexp_of_string "reference";
-    Sexplib0.Sexp_conv.sexp_of_string reference
-  ]
-
-let t_of_sexp sexp =
-  match sexp with
-  | Sexplib0.Sexp.List [ _; part_sexp; _; ref_sexp ] ->
-      let part = part_of_sexp part_sexp in
-      let reference = Sexplib0.Sexp_conv.string_of_sexp ref_sexp in
-      { part; reference }
-  | _ -> Sexplib0.Sexp_conv.of_sexp_error "Citation.t_of_sexp: expected record format" sexp
+type t = { part : part; reference : string } [@@deriving sexp]
diff --git a/lib/kernel/citation.mli b/lib/kernel/citation.mli
index 74cd639..4e6ddb5 100644
--- a/lib/kernel/citation.mli
+++ b/lib/kernel/citation.mli
@@ -7,6 +7,3 @@ val part_to_string : part -> string
 val part_of_string : string -> part option
 
 type t = { part : part; reference : string } [@@deriving sexp]
-
-val sexp_of_t : t -> Sexplib0.Sexp.t
-val t_of_sexp : Sexplib0.Sexp.t -> t
diff --git a/lib/kernel/date_spec.ml b/lib/kernel/date_spec.ml
index 1d0da00..76e21e3 100644
--- a/lib/kernel/date_spec.ml
+++ b/lib/kernel/date_spec.ml
@@ -1,8 +1,10 @@
+open Sexplib0.Sexp_conv
+
 (* How a sanctoral entry expresses its date. Plan 2 ships the only form the EF
    sanctoral needs -- a fixed calendar date -- because EF movable feasts come
    from the rite's temporal code, not from data. Sunday-relative and
    Easter-relative forms arrive with the OF sanctoral. *)
-type t = Fixed of { month : int; day : int }
+type t = Fixed of { month : int; day : int } [@@deriving sexp]
 
 (* Leap-year maximum, so 29 February is constructible; it simply does not
    resolve in a common year. *)
@@ -21,33 +23,3 @@ let fixed ~month ~day =
 let resolve t ~year =
   match t with
   | Fixed { month; day } -> Result.to_option (Date.make ~year ~month ~day)
-
-let sexp_of_t = function
-  | Fixed { month; day } ->
-      Sexplib0.Sexp.List [
-        Sexplib0.Sexp_conv.sexp_of_string "Fixed";
-        Sexplib0.Sexp.List [
-          Sexplib0.Sexp.List [
-            Sexplib0.Sexp_conv.sexp_of_string "month";
-            Sexplib0.Sexp_conv.sexp_of_int month
-          ];
-          Sexplib0.Sexp.List [
-            Sexplib0.Sexp_conv.sexp_of_string "day";
-            Sexplib0.Sexp_conv.sexp_of_int day
-          ]
-        ]
-      ]
-
-let t_of_sexp sexp =
-  match sexp with
-  | Sexplib0.Sexp.List [
-      Sexplib0.Sexp.Atom "Fixed";
-      Sexplib0.Sexp.List [
-        Sexplib0.Sexp.List [ Sexplib0.Sexp.Atom "month"; month_sexp ];
-        Sexplib0.Sexp.List [ Sexplib0.Sexp.Atom "day"; day_sexp ]
-      ]
-    ] ->
-      let month = Sexplib0.Sexp_conv.int_of_sexp month_sexp in
-      let day = Sexplib0.Sexp_conv.int_of_sexp day_sexp in
-      Fixed { month; day }
-  | _ -> Sexplib0.Sexp_conv.of_sexp_error "Date_spec.t_of_sexp: expected Fixed record format" sexp
diff --git a/lib/kernel/date_spec.mli b/lib/kernel/date_spec.mli
index 600f1eb..3fe9625 100644
--- a/lib/kernel/date_spec.mli
+++ b/lib/kernel/date_spec.mli
@@ -1,9 +1,6 @@
 (** A sanctoral entry's date expression. *)
 type t = Fixed of { month : int; day : int } [@@deriving sexp]
 
-val sexp_of_t : t -> Sexplib0.Sexp.t
-val t_of_sexp : Sexplib0.Sexp.t -> t
-
 (** Validates against the leap-year maximum, so 29 February is constructible. *)
 val fixed : month:int -> day:int -> (t, string) result
 
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)
diff --git a/lib/kernel/names.mli b/lib/kernel/names.mli
index 567ce2e..e3398d9 100644
--- a/lib/kernel/names.mli
+++ b/lib/kernel/names.mli
@@ -2,9 +2,6 @@
     kept sorted by language code, so equal name sets have equal sexp forms. *)
 type t = (Lang.t * string) list [@@deriving sexp]
 
-val sexp_of_t : t -> Sexplib0.Sexp.t
-val t_of_sexp : Sexplib0.Sexp.t -> t
-
 val empty : t
 
 (** Canonicalises; on duplicate languages the last entry wins. *)