When there is a package conflict, state where the dependencies come from

[RalfJung]

I am trying to figure out why opam fails saying

[ERROR] Package conflict!
  * Missing dependency:
    - coq-stdpp (>= 2022-08-12.3.d6c6e66a & < dev.2017-11-12.2)
    no matching version

Sadly this is on CI, so I have no way to directly interact with that state. And the message makes no sense, no package involved should have a constraint that says < dev.2017-11-12.2. It would help enormously if opam could say why it thinks that there is a < dev.2017-11-12.2 constraint; as-is, these error messages are not very useful.

# opam config report
# opam-version         2.1.1 
# self-upgrade         no
# system               arch=x86_64 os=linux os-distribution=debian os-version=10
# 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                 20
# repositories         2 (http), 1 (version-controlled) (default repo at 3927b22a)
# pinned               4 (rsync), 2 (version)
# current-switch       default
# ocaml:native         true
# ocaml:native-tools   true
# ocaml:native-dynlink true
# ocaml:stubsdir       /builds/iris/iris/_opam/default/lib/ocaml/stublibs:/builds/iris/iris/_opam/default/lib/ocaml
# ocaml:preinstalled   false
# ocaml:compiler       4.07.1
<><> Repository configuration for switch default ><><><><><><><><><><><><><><><>
[NOTE] These are the repositories in use by the current switch. Use '--all' to see all configured repositories.
 1 iris-dev     git+https://gitlab.mpi-sws.org/iris/opam.git
 2 coq-released https://coq.inria.fr/opam/released
 3 default      https://opam.ocaml.org/

[RalfJung]

In this case it turns out the issue was a = 2022-08-12.3.d6c6e66a should have been = dev.2022-08-12.3.d6c6e66a. That still does not satisfy the < dev.2017-11-12.2 constraint, but that constraint does not really exist, so then things went fine.

[kit-ty-kate]

This is a duplicate of #4373. Could you add your comment there with:

• the available repositories hashes
• the switch invariant
• the list of pinned packages
• the current system
• the command showing the conflict message

and close this issue?

[RalfJung]

Uh, no idea how to get all that information, sorry.

• The available repositories are listed above.
• The switch invariant is whatever you get from creating a switch with ocaml-variants.4.14.0+options ocaml-option-flambda
• "current system", no idea what you mean by that, I gave the opam config report above
• the command is this line in our CI scripts

You can see the full CI logs here.

I also now remember that & in these messages often means "or" (completely defying the meaning of that symbol basically everywhere else, including in opam's own syntax), so that is probably part of the problem here.

[kit-ty-kate]

This should have been fixed by #6106 released in opam 2.3.0. If you still have some issues, feel free to reopen or open a new ticket. Thanks for the report!