Isolate .cargo directory inside .pixi directory

[jonmmease]

Hi, I'm working on moving my VegaFusion project to pixi. This is a project with a Rust core and wrappers in Python, wasm / JavaScript, and Java. The current development setup is a bit of a hassle involving the system installation of rust/cargo, node, protobuf, and conda/conda.lock. I'd like to see if I can isolate all of this with pixi, as conda-forge already provides rust/cargo, node, and protobuf.

This seems to be working out pretty well so far (it's still a WIP), but I had one idea that I think would improve the situation a bit. I noticed that the rust installation from conda-forge still creates a ~/.cargo directory for the cargo cache and it places any globally installed executables in ~/.cargo/bin. It would be great to have a clean way to put this .cargo directory inside the .pixi folder, and to add the .cargo/bin directory to the path for use in tasks and in pixi shell. This would make it possible to build a rust project without a system installation of rust, and without leaving any traces of Rust configuration outside of the project's pixi directory.

As a side note, the reason I need .cargo/bin on the path is because I'm using cargo to install wasm-pack, which doesn't seem to be available on conda-forge at this point.

Here's one approach that comes to mind. It's possible to move the .cargo directory by setting the CARGO_HOME environment variable, so if there was a way to set environment variables in pixi.toml that would be used across tasks and in pixi shell, that would make it possible to move the .cargo directory to .pixi/.cargo. And if it were possible to add additional directories inside .pixi to the PATH, then it would be possible to add .pixi/.cargo/bin to the path for use in tasks and pixi shell.

[wolfv]

Hey @jonmmease, I think we have two options:

• we could add a CARGO_HOME variable to the activation script of the Rust feedstock (that would change this behavior for everyone though)
• we are working on adding environment variable support to pixi run, so that you could set / override whatever env vars you'd like

I am not sure if everyone that uses the rust feedstock would prefer to not share their cargo cache ... so I am a bit unsure. We'll for sure work on adding environment variable support in pixi though.

[jonmmease]

Thanks for the response. I think I'd prefer the environment variable approach (and glad to hear you're working on it!), as there's probably an argument for keeping.cargo in the default location in order to share the cache across conda environments in certain situations.

[twrightsman]

I think setting CARGO_HOME in the feedstock is actually a good idea as well, because then Conda environments are more isolated from the system and each other, as they should be?