Looking for suggestions for PPX rewriters that need creating

I posted recently about writing a “hashcons” PPX rewriter in order to re-share as much of an AST as is possible, when doing multiple top-down/bottom-up passes on an AST (e.g., when chaining multiple PPX rewriters, haha). That’s finished, and I’m looking for other ideas for PPX rewriters. It seems pretty clear that writing new PPX rewriters is not for the faint of heart, so perhaps there are people who read this forum, who have ideas for rewriters that they’d like to see in the world, but don’t have the time and knowledge of the Ocaml AST, to be able to write.

Right now, my TODO list is:
ppx_deriving.make: doing this now
ppx_deriving.yojson, ppx_deriving.sexp, ppx_deriving.protobuf

But this won’t take more than a few days. So: if somebody has ideas, I’d love to hear them.

Thanks in advance,


Please also keep in mind plans for using the “new” PPX abstraction layer, which is based somewhat on the ppxlib interface (see the announce at this forum - The future of ppx).

For deriving plugins see those:

So please keep those in mind, maybe help to review or update the PRs, and work on the protobuf one.

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ppx_deriving.capnp would be a good one - capnp specification