Managing external dependencies on macOS

Learning
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1

Hi there,

Recently I wanted to install the cvc5 package. It depends on conf-python3-pyparsing, which is marked as != macos. I tried to see why this is, and it seems to be because it (naturally) requires the pyparsing library to be installed. Currently I believe opam external dependencies on macOS are managed with homebrew, however homebrew does not have this python package.

I tried to contribute this package to homebrew, however they no longer support python packages in general. Should the way external dependencies are managed on macOS change because of this? I seem to have hit a wall resolving my “dependency tree“ for installing the cvc5 library on macOS.

More interestingly, I happen to not use homebrew to manage dependencies, and I use instead opam-nix. However this seems to completely block me as a macOS user. I was wondering if anyone had tips on how to resolve this, and whether maybe defaulting to homebrew being associated with macOS is no longer the way to go.

Thanks!

Tiago

2

I think this is an error in opam-repository. conf-* pakages shouldn’t be marked unavailable on platforms that happen to not package them unless it happens to be a tool or feature uninstallable on these platforms (e.g. conf-linux-libc-dev).

Would you be able to open a PR to update conf-python3-pyparsing’s definition by removing the available: field and replacing it with x-ci-accept-failures: ["macos-homebrew"] ?

3

That makes sense, will do, thank you!

On that note I came across this article on opam’s nix support, which sounds super exciting! I was wondering, is there some hope that this could work for macOS, or is this only for NixOS?

4

Great question. We haven’t specifically tested nix on macOS but it should work.
If you have opam >= 2.4.0 you should be able to try it out using:

opam var --global os-distribution=nixos
opam var --global os-family=nixos

However note that there are currently no CI running on opam-repository that test this combination, so occasional failures might occur.

5

Will give that a try, thanks!

In any case this is probably great for opam-nix too. Currently macOS dependencies are mapped to equivalent nixpkgs dependencies. However it should be adapted to use the nixos entry directly if available.