Supporting the optional flag

[pbiggar]

ppx_deriving supports an optional flag. From their docs:

It's possible to make deriving ignore a missing plugin rather than raising an error by passing an optional = true option, for example, to enable conditional compilation:

type addr = string * int
[@@deriving yojson { optional = true }]

This works well for their builtins, but doesn't seem to work for bin_io - which is making writing platform independent code difficult. Would you be able to support it?

[hhugo]

I believe this issue belongs to https://github.com/ocaml-ppx/ppxlib

[pbiggar]

Thanks @hhugo, will report it there.

[aalekseyev]

Closing this one.