[kdkeyser]

I second this. I dislike the liberal usage of metaprogramming, especially in the context of a code base that you have to work on with multiple people. It adds another layer of concepts/complexity/magic that everyone in the team has to learn.

With PPX, the barrier to use metaprogramming has become lower (especially compared to camlp4), resulting in most modern Ocaml codebases depending on it. But the ergonomics of the end-to-end software delivery have not really followed: the fact that PPX's break between compiler versions means that in practice, a compiler upgrade becomes a very costly thing to do. It is difficult to make the case for this in an industrial setting, where languages with almost religious backwards compatibility are common (Java, C++, even Go). For Ocaml, it is especially sad, because the core language is already quite powerful and expressive, lowering the need for metaprogramming (imo).

For scenarios where code generation is needed, I prefer a separate code generation step, which produces explicit "standard" code (e.g. like protoc)