[new release] ppx_deriving (6.0.0)

[NathanReb]

Type-driven code generation for OCaml

• Project page: https://github.com/ocaml-ppx/ppx_deriving
• Documentation: https://ocaml-ppx.github.io/ppx_deriving/

CHANGES:

• Fix a bug in [@@deriving make] that caused errors when it was used on a set
  of type declarations containing at least one non record type.
  Fix a bug with [@@deriving make] on type declarations sets ocaml-ppx/ppx_deriving#281
  (@NathanReb)

• Embed errors instead of raising exceptions when generating code
  with ppx_deriving.make
  Fix a bug with [@@deriving make] on type declarations sets ocaml-ppx/ppx_deriving#281
  (@NathanReb)

• Remove [%derive.iter ...], [%derive.map ...] and [%derive.fold ...]
  extensions
  Remove extensions from fold, iter and map plugins ocaml-ppx/ppx_deriving#278
  (Simmo Saan)

• Port standard plugins to ppxlib registration and attributes
  Port standard plugins to ppxlib registration and attributes ocaml-ppx/ppx_deriving#263
  (Simmo Saan)

• Optimize forwarding in eq and ord plugins
  Optimize forwarding in eq and ord plugins ocaml-ppx/ppx_deriving#252
  (Simmo Saan)

• Delegate quoter to ppxlib
  Port standard plugins to ppxlib registration and attributes ocaml-ppx/ppx_deriving#263
  (Simmo Saan)

• Introduce Ppx_deriving_runtime.Stdlib with OCaml >= 4.07.
  This module already exists in OCaml < 4.07 but was missing otherwise.
  Add OCaml 5.00 support to the tests and update documentation ocaml-ppx/ppx_deriving#258
  (Kate Deplaix)

[sim642]

Most CI errors seem to be related to ocaml-ppx/ppx_deriving#279 (which isn't in the changelog):

#=== ERROR while compiling ppx_deriving_yojson.3.7.0 ==========================#
# context              2.2.0~beta3~dev | linux/x86_64 | ocaml-base-compiler.4.14.2 | file:///home/opam/opam-repository
# path                 ~/.opam/4.14/.opam-switch/build/ppx_deriving_yojson.3.7.0
# command              ~/.opam/opam-init/hooks/sandbox.sh build dune build -p ppx_deriving_yojson -j 39
# exit-code            1
# env-file             ~/.opam/log/ppx_deriving_yojson-7-9f30e6.env
# output-file          ~/.opam/log/ppx_deriving_yojson-7-9f30e6.out
### output ###
# (cd _build/default && /home/opam/.opam/4.14/bin/ocamlc.opt -w -40 -g -bin-annot -I src/.ppx_deriving_yojson_runtime.objs/byte -I /home/opam/.opam/4.14/lib/ppx_deriving/runtime -I /home/opam/.opam/4.14/lib/result -intf-suffix .ml -no-alias-deps -o src/.ppx_deriving_yojson_runtime.objs/byte/ppx_deriving_yojson_runtime.cmo -c -impl src/ppx_deriving_yojson_runtime.ml)
# File "src/ppx_deriving_yojson_runtime.ml", line 20, characters 32-45:
# 20 | type 'a error_or = ('a, string) Result.result
#                                      ^^^^^^^^^^^^^
# Error: Unbound type constructor Result.result
# (cd _build/default && /home/opam/.opam/4.14/bin/ocamlopt.opt -w -40 -g -I src/.ppx_deriving_yojson_runtime.objs/byte -I src/.ppx_deriving_yojson_runtime.objs/native -I /home/opam/.opam/4.14/lib/ppx_deriving/runtime -I /home/opam/.opam/4.14/lib/result -intf-suffix .ml -no-alias-deps -o src/.ppx_deriving_yojson_runtime.objs/native/ppx_deriving_yojson_runtime.cmx -c -impl src/ppx_deriving_yojson_runtime.ml)
# File "src/ppx_deriving_yojson_runtime.ml", line 20, characters 32-45:
# 20 | type 'a error_or = ('a, string) Result.result
#                                      ^^^^^^^^^^^^^
# Error: Unbound type constructor Result.result

Maybe existing versions of it need an upper bound on ppx_deriving now. A new version of ppx_deriving_yojson including ocaml-ppx/ppx_deriving_yojson#153 is probably needed.

[NathanReb]

It looks to me like this errors are side effects of this change indeed but come from the fact that those package use Result without explicitly depending on it.

The fix is likely to add that dependency to ppx_deriving_yojson, I'll take care of that!

[NathanReb]

Okay this is more complicated than I thought. While removing result we seem to have messed up Ppx_deriving_runtime which for some reason re-includes the standard library in a weird way.

Since we removed an overriden Result module there that was defining the type equality ('a, 'err) t = ('a, 'err) result (which is already defined by the result compat package btw), including Ppx_deriving_runtime as is done in ppx_deriving_yojson makes the standard Result module shadow the compat one and therefore causes this error because the standard Result module does not define a result type, only t.

[NathanReb]

We could either add an upper bound on ppx_deriving in ppx_deriving_yojson or simply fix this small part of the change in ppx_deriving.

Given both ppx_deriving.api and ppx_deriving.runtime are to be deprecated, I'd be slightly in favor of fixing this in ppx_deriving so it has one last clean version before we deprecate the deriver creation API.

[NathanReb]

I'm closing once again, will release 6.0.1 with the fix to Ppx_deriving_runtime.