Failure("unknown variant: options")

2023-01-19 22:28.50: >>> Failure("unknown variant: options") (score = 30)
2023-01-19 22:28.50: >>> Failure("unknown variant: options") (score = 30)
2023-01-19 22:28.50: unknown variant: options

https://ci.ocamllabs.io/github/ocsigen/lwt/commit/3d6f0fac4fed71d3c9cbdc5b90d6a443949bb0d6/variant/(analysis)

This issue seems to come from
https://github.com/ocurrent/ocaml-version/blob/5b5413a42c3a9e3c10ca0a9b247ef11c78b23b9b/ocaml_version.ml#L599
the only place afaict that introduces the variant "options". It is however not present in
https://github.com/ocurrent/ocaml-version/blob/5b5413a42c3a9e3c10ca0a9b247ef11c78b23b9b/ocaml_version.ml#L412-L425
so there's an error at
https://github.com/ocurrent/ocaml-version/blob/5b5413a42c3a9e3c10ca0a9b247ef11c78b23b9b/ocaml_version.ml#L456-L461

I can't manage to prove that this is where the "options" variant was introduced in the version value, nor find another place where it might have, nor figure out why the extra field isn't None in Opam.V2.package.

cc @benmandrew who first found the issue.
cc @dra27 who might have a clue?

Start with the CI failure linked in the issue, then inspect ocaml_version.ml around lines 412-425, 456-461, and 599. Trace how the "options" variant enters the version value and why the extra field is not None in Opam.V2.package. Done means identifying the source of the unexpected variant and correcting the parsing or version handling.