Allow profile to be set by SETUPTOOLS_RUST_CARGO_PROFILE env variable

[jefferyto]

This allows the profile to be set dynamically, without having to edit pyproject.toml/setup.py.

[davidhewitt]

I understand the desire for this (and have wanted it myself) but would like this to be called something other than CARGO_PROFILE as cargo itself does not recognise that environment variable. Perhaps a PR to cargo to implement this upstream would solve your use case and also help more users?

[jefferyto]

Perhaps a PR to cargo to implement this upstream would solve your use case and also help more users?

This would be better but I don't have time to wade into cargo internals right now 😅 I couldn't find any mention of this functionality in their issues/PRs, that is slightly surprising.

Also it turns out CARGO_PROFILE is already used to enable an internal profiler, so that name is probably a no-go already.

Would SETUPTOOLS_RUST_PROFILE or SETUPTOOLS_RUST_CARGO_PROFILE be acceptable?

[jefferyto]

I have changed the variable name to SETUPTOOLS_RUST_CARGO_PROFILE.

FYI I'm the Python maintainer at the OpenWrt packages feed; I'm working on improving the building of Rust extensions for the Python packages there. It would be much easier to patch setuptools-rust to accept this environment variable than to patch args=["--profile=..."] (and reading from an environment variable) into every Python package that needs it. (The profile selected would be determined by the OpenWrt build system.)

I'm not a Rust person so getting this isn't cargo isn't my first choice/priority right now.

[davidhewitt]

Sorry for the delayed reply. Understood, in which case to help you move forward let's accept the environment variable here for now.

Can you please add a CHANGELOG entry, and then I'll get this merged and released asap.

[jefferyto]

Thanks 🙏 I've updated the CHANGELOG.

[jefferyto]

Reformatted with black.

[davidhewitt]

Thanks! Will ship now 👍