Erroneous message/return code with opam remove when are unavailable

[thierry-martinez]

I am facing some failures with opam-ci while trying to package libclang (ocaml/opam-repository#19824), and I don't understand the opam behavior here.

In the docker container created by opam-ci (based on the image ocaml/opam:alpine-3.13-ocaml-4.13), the command opam remove conf-libclang.12 fails with the following error:

[ERROR] Package conf-libclang.12 depends on the unavailable system package
        'llvm-dev'. You can use `--no-depexts' to attempt installation anyway.

I am a bit surprised that opam remove can fail on an uninstalled package for an unavailable dependency, but more surprisingly this package is available on the system: sudo apk add llvm-dev successfully installs llvm!

Moreover, if I try opam install --deps-only conf-libclang.12 (before installing the llvm-dev package manually via apk), the command answers Nothing to do..

Any hint about how to fix that? Thank you very much.

bash-5.1$ opam config report
# opam config report
# opam-version         2.1.0 (9c5bd41377e24f7409cf35ac83bfddeed01265e6) 
# self-upgrade         no
# system               arch=x86_64 os=linux os-distribution=alpine os-version=3.13.6
# solver               builtin-mccs+glpk
# install-criteria     -removed,-count[avoid-version,changed],-count[version-lag,request],-count[version-lag,changed],-count[missing-depexts,changed],-changed
# upgrade-criteria     -removed,-count[avoid-version,changed],-count[version-lag,solution],-count[missing-depexts,changed],-new
# jobs                 47
# repositories         1 (local)
# pinned               2 (version)
# current-switch       4.13
# ocaml:native         true
# ocaml:native-tools   true
# ocaml:native-dynlink true
# ocaml:stubsdir       /home/opam/.opam/4.13/lib/ocaml/stublibs:/home/opam/.opam/4.13/lib/ocaml
# ocaml:preinstalled   false
# ocaml:compiler       4.13.1

[rjbou]

related to #4759 (comment)

[rjbou]

Thanks for the report!
Some more complete answers:

I am a bit surprised that opam remove can fail on an uninstalled package for an unavailable dependency,

In fact, it is not failing, the error message is misleading (and wrong) and the error code too. There is no removal possible as the package is not installed; If the package were installed, it would be another message, a warning that system dependency is no more in the system, and then package removal.

but more surprisingly this package is available on the system: sudo apk add llvm-dev successfully installs llvm!

It is a virtual package, and this is not handled for alpine yet, as pointed in linked issue.

Moreover, if I try opam install --deps-only conf-libclang.12 (before installing the llvm-dev package manually via apk), the command answers Nothing to do..

This one is an expected behavior. conf-libclang have no opam dependencies (depends: field empty), so when you try to install its opam dependencies, opam have nothing to do.. Maybe you wanted opam install conf-libclang --depexts-only?

[thierry-martinez]

Thank you for your answer!

In fact, it is not failing, the error message is misleading (and wrong) and the error code too. There is no removal possible as the package is not installed; If the package were installed, it would be another message, a warning that system dependency is no more in the system, and then package removal.

Ok, I think I understand better now. Any chance that opam would exit with error code 0 in this case? The current behaviour seems to break opam-ci for centos as soon as there is a package with an external dependency, isn't it?

It is a virtual package, and this is not handled for alpine yet, as pointed in linked issue.

Indeed. Thank you very much for the reference to the other issue.

This one is an expected behavior. conf-libclang have no opam dependencies (depends: field empty), so when you try to install its opam dependencies, opam have nothing to do.. Maybe you wanted opam install conf-libclang --depexts-only?

You are right, I made a confusion between --deps-only and --depexts-only while reading the command-line that opam-ci executed.

[rjbou]

Any chance that opam would exit with error code 0 in this case?
Completely, I'll keep this issue open to track/fix that.

[kit-ty-kate]

(somewhat) related to #4493

[rjbou]

fixed by #4995