macOS platform hack does not pick up workspace cargo configuration

[evnu]

The platform hack for macOS does not consider a cargo configuration within a workspace, but only the configuration local to a crate. This results in unnecessary warnings when the correct arguments are already provided within the workspace-wide configuration.

[evnu]

To fix this, the check should be extended by also checking the workspace root for a configuration. The workspace root can be extracted from cargo metadata, but that command returns JSON.

[scrogson]

@evnu would you be able to create a repo with this setup so I can tinker with a fix?

[evnu]

This should reproduce the problem: https://github.com/evnu/NifIo/tree/macos-platform-hack

git clone https://github.com/evnu/NifIo.git
git checkout macos-platform-hack
mix deps.get
mix compile

I added a Cargo.toml to the projects root directory with a single workspace member, and a dummy .cargo/config as well.

~/tools/NifIo(macos-platform-hack ✗) cargo metadata --format-version 1 | jq ".workspace_root"
"/home/mo/tools/NifIo"
~/tools/NifIo(macos-platform-hack ✗) cd native/io 
~/tools/NifIo/native/io(macos-platform-hack ✗) cargo metadata --format-version 1 | jq ".workspace_root"
"/home/mo/tools/NifIo"

[evnu]

@scrogson Any update here?

[scrogson]

I haven't spent any time thinking about this. Do we want to pull in a JSON library to remove a warning? I think the answer is no.

Given that you have more experience with this setup, what do you think?

[scrogson]

I guess we could just check the root first and then fallback to the crate_path: https://github.com/rusterlium/rustler/blob/master/rustler_mix/lib/mix/tasks/compile.rustler.ex#L120

[evnu]

I also don't think that we should use a json library just for this. To get the workspace root, we might don't need to parse json, a regex could suffice. I can give that a try.

[evnu]

See #381, we might need to parse the JSON produced by cargo metadata there. If so, maybe we can pick up this issue here again to find the proper configuration for a crate.