Error while installing cppo_ocamlbuild package via OPAM

[db4]

I'm trying to install cppo_ocamlbuild for OCaml 4.02.3 via OPAM. With dune 1.0.0 it worked but now (after upgrade to dune 1.2.0) I get an error:

#=== ERROR while installing cppo_ocamlbuild.1.6.0 =============================#
# opam-version 1.2.2
# os           linux
# command      jbuilder build -p cppo_ocamlbuild -j 4
# path         /home/dbely/.opam/4.02.3+local+gcc5+x64+fpic/build/cppo_ocamlbuild.1.6.0
# compiler     4.02.3+local+linux+fpic
# exit-code    1
# env-file     /home/dbely/.opam/4.02.3+local+gcc5+x64+fpic/build/cppo_ocamlbuild.1.6.0/cppo_ocamlbuild-28557-320155.env
# stdout-file  /home/dbely/.opam/4.02.3+local+gcc5+x64+fpic/build/cppo_ocamlbuild.1.6.0/cppo_ocamlbuild-28557-320155.out
# stderr-file  /home/dbely/.opam/4.02.3+local+gcc5+x64+fpic/build/cppo_ocamlbuild.1.6.0/cppo_ocamlbuild-28557-320155.err
### stderr ###
# [...]
# 5 | (ocamlyacc (cppo_parser))
#     ^^^^^^^^^^^^^^^^^^^^^^^^^
# Warning: File cppo_parser.mli is both generated by a rule and present in the source tree.
# As a result, the rule is currently ignored, however this will become an error in the future.
# To keep the current behavior and get rid of this warning, add a field (fallback) to the rule.
# File "ocamlbuild_plugin/jbuild", line 8, characters 14-24:
# 8 |   (libraries (ocamlbuild))))
#                   ^^^^^^^^^^
# Error: Library "ocamlbuild" not found.
# Hint: try: dune external-lib-deps --missing -p cppo_ocamlbuild @install

[db4]

OK, I've finally found the problem. cppo_ocamlbuild actually requires ocamlfind to find ocamlbuild library, which is not specified in its dependencies. So then I deploy OPAM and packages in a fresh environment, ocamlfind may not be installed before cppo_ocamlbuild build.

[mjambon]

I'm no ocamlbuild user myself. I see there's an ocamlbuild-pkg which seems to have the correct dependencies. So, perhaps the fix is to replace the ocamlbuild dependency by ocamlbuild-pkg in the opam package for cppo_ocamlbuild. Please confirm and/or submit a pull request to opam-repository.

[db4]

Someone else has independently found and fixed that: ocaml/opam-repository#12640

[mjambon]

Great. The corresponding PR is at ocaml/opam-repository#12782.
We can close this issue when that PR gets merged.

[db4]

ocaml/opam-repository#12782 is merged so closing the issue.