Making other deriving plugins work on 4.05

[infinity0]

8705088 added 4.05 support but also changed the command-line interface of the ppx_deriving program so that plugin names need to be prefixed with an extra -deriving-plugin flag. This is causing build failures like mirleft/ocaml-nocrypto#122. I'm not sure how to tell the tooling to pass this flag in, but it seems like it should be done automatically by ppx_deriving rather than requiring everyone to edit their build scripts.

[gasche]

This should be fixed by #141 once it is merged.

[samoht]

Yes please :-)

[whitequark]

Triage: #141 merged but other derivers still broken, more work required.

[infinity0]

Part of the discussion there suggested that certain Jane Street packages need an update, I was able to build stuff using their development repo. @diml ?

[ghost]

This affects me as well, and we're already in 4.06's beta cycle. Any predictions when this (and ocaml-ppx/ppx_deriving_yojson#56) will be resolved?

[gasche]

We have a plan for a maintenance release of ppx-deriving 4.1, in the next few days, to support OCaml 4.05 and 4.06. Hopefully we can also do the same for ppx_deriving_yojson. So I would say that the current plan is to resolve this within the week. Sorry for the slow time working out the best short-term solution.

[ghost]

@gasche, sounds good. If you don't mind, please keep us updated here.

[gasche]

Update: I have updates in the pipeline for ppx_deriving to support 4.05 and 4.06, and the plan is to make a maintenance release of ppx_deriving 4.2 first, and then release plugins on top of it (ppx_deriving_{hardcaml,protobuf,yojson}) which also have their 4.06-support PRs.

[gasche]

@Tuncer ppx_deriving 4.2.1 was just released with support for 4.05 and 4.06. If you are a user of ppx_deriving, feedback on whether this release works for you would be very useful. Note that the ppx_deriving plugins (yojson, protobuf etc.) have not been updated yet, but this should come shortly.

If the driverization change in 4.2 proves to still break user's code, I will make a maintenance release of the 4.1 version, but hopefully 4.2 works.

[ghost]

@gasche, out of the various packages I install in each switch by default, ulex is the only one that's still 4.06-incompatible, and that has been fixed today (ocaml-community/ulex@306f31f). But it's not released into opam yet.

Was I not supposed to be able to install yojson? It works for me.

[gasche]

ppx_deriving_yojson does not compile under 4.06 ( see pull request to fix this at ocaml-ppx/ppx_deriving_yojson#66 ). You may be using just the yojson package, or another ppx-deriver for it.

[ghost]

Right, it's just yojson.

[shonfeder]

I just switched to 4.06 to try this out. I think I must be doing something wrong, as trying to install ppx_deriving gives a constraint violation, and trying to pin ppx_deriving to 4.2.1 says that no such version exists:

$ opam switch show
4.06.0

$ opam --version
1.2.2

$ opam install ppx_deriving
[ERROR] ppx_deriving is not available because your system doesn't comply with ocaml-version > "4.03.0" & opam-version >= "1.2"
        & ocaml-version < "4.06.0".

$ opam install ppx_deriving 4.2.1
[ERROR] No package named 4 found.

$ opam pin add ppx_deriving 4.2.1
[ERROR] Package ppx_deriving has no version 4.2.1

(Just to be clear, while I am fighting my own battles with ppx_deriving and yojson, this is meant as an attempt to "be useful" rather than a complaint.)

[ghost]

@shonfeder, it's still 4.2 (not 4.2.1) in the opam repo. Though to be clear, I wasn't installing ppx_deriving explicitly, and whatever else has been made compatible with 4.06 was enough for me to miss just ulex. Sorry, if my success report was misleading.

[gasche]

No, 4.2.1 should be in the opam repo now, you should see it with opam update. @shonfeder the syntax is opam install ppx_deriving.4.2.1, not ppx_deriving 4.2.1, to force a specific version.

[shonfeder]

Ah! My mistake. Thank, you @gasche, that worked for the installation.

[ghost]

Confirmed it's visible in opam now.

[kit-ty-kate]

(this looks fixed so i closed it)