kernel(lectionary): fix round 1 -- load never raises

Sexplib.Sexp.load_sexp raises bare Failure for several malformed inputs
(unterminated list/string, empty file, more than one sexp) rather than
Sexplib.Sexp.Parse_error, so those cases escaped Lectionary.load as an
uncaught exception -- breaking the .mli's own promise and the kernel's
never-raises-on-fallible-construction constraint. Mirrors the catch-all
already present in Layer.load and Overlay.load, plus a second catch-all
on the t_of_sexp branch for defence in depth.

Adds test_load_never_raises, covering all of the above plus a missing
file, using Filename.temp_file rather than a hardcoded path. Verified the
new test fails against the pre-fix load (uncaught Failure) and passes
against the fix.

1 files changed, 26 insertions, 1 deletions

diff --git a/test/test_lectionary.ml b/test/test_lectionary.ml
index 45a01ab..fba890a 100644
--- a/test/test_lectionary.ml
+++ b/test/test_lectionary.ml
@@ -53,8 +53,33 @@ let test_sexp_round_trip () =
   let l' = Lectionary.t_of_sexp (Lectionary.sexp_of_t l) in
   Alcotest.(check bool) "round trips" true (l = l')
 
+let with_temp_file contents f =
+  let path = Filename.temp_file "lectionary_test" ".sexp" in
+  let oc = open_out path in
+  output_string oc contents;
+  close_out oc;
+  Fun.protect ~finally:(fun () -> Sys.remove path) (fun () -> f path)
+
+let load_is_error contents what =
+  with_temp_file contents (fun path ->
+      match Lectionary.load path with
+      | Error _ -> ()
+      | Ok _ -> Alcotest.fail (what ^ ": expected Error, got Ok"))
+
+let test_load_never_raises () =
+  load_is_error "((ef-advent-sunday-1 (" "unterminated list";
+  load_is_error "((ef-advent-sunday-1 ((part First) (reference \"x" "unterminated string";
+  load_is_error "" "empty file";
+  load_is_error "() ()" "more than one sexp";
+  load_is_error "not-a-list" "wrong shape";
+  load_is_error "((\"NOT A SLUG\" ()))" "invalid slug";
+  match Lectionary.load "/nonexistent/path/lectionary.sexp" with
+  | Error _ -> ()
+  | Ok _ -> Alcotest.fail "missing file: expected Error, got Ok"
+
 let suite =
   [ ("find present", `Quick, test_find_present);
     ("find absent", `Quick, test_find_absent);
     ("duplicate slug rejected", `Quick, test_duplicate_slug_rejected);
-    ("sexp round-trip", `Quick, test_sexp_round_trip) ]
+    ("sexp round-trip", `Quick, test_sexp_round_trip);
+    ("load never raises", `Quick, test_load_never_raises) ]