[Caml-list] [ANN] ppx_deriving 3.0

[whitequark <whitequark@whitequark.org>]

Hello,

I am glad to announce ppx_deriving 3.0. It brings two
major changes: hygiene and ppx_type_conv compatibility.
It is installable via opam[1].

First, hygiene. Earlier versions of ppx_deriving:
   1) assumed that all the modules that the deriver
      requires are not shadowed with a different signature;
   2) included user-specified code such as from [@default]
      attributes in a way that exposed deriver-internal
      identifiers to such code.

Now, ppx_deriving includes a mechanism for hygienic
unquoting[2], as well as a module[3] containing references
to most standard library modules under their proper names.
This allows it to coexist with e.g. `open Core.Std`.

Second, ppx_type_conv compatibility. You probably don't
know it yet, but Jane Street has converted all their syntax
extensions to ppx, so now there's ppx_type_conv, ppx_sexp_conv,
etc. I've coordinated the development of ppx_deriving with
Jane Street, so now ppx_deriving and ppx_type_conv use
the same syntactic conventions. In fact, they share
the [@@deriving] syntax without any effort from the user!

Furthermore, I have been looking at the sources of Jane Street's
ppx_core, ppx_driver, ppx_type_conv, etc and I find these
projects exceptionally well designed; further, they tackle some
important problems that ppx_deriving has explicitly left out of
scope, such as attribute hygiene.

While these libraries have a somewhat larger API, I think anyone
writing a new deriver should consider using ppx_type_conv.
I cannot outright recommend that since I have not actually
tried it (yet?), but it sounds worthwhile.

[1]: http://opam.ocaml.org/packages/ppx_deriving/ppx_deriving.3.0/
[2]: 
https://whitequark.github.io/ppx_deriving/Ppx_deriving.html#2_Hygiene
[3]: https://whitequark.github.io/ppx_deriving/Ppx_deriving_runtime.html

-- 
whitequark