rustup no longer automatically installs the right toolchain

[bergkvist]

See https://blog.rust-lang.org/2025/03/02/Rustup-1.28.0.html

Before this change, I could add a rust-toolchain.toml file to my Python-project, and setuptools-rust would automatically install the right toolchain before building.

Now, before building it is neccesary to run the following command manually (in the same folder as the rust-toolchain.toml file):

rustup toolchain install

It would be nice if there was a way to configure setuptools-rust with a flag to run this command before issuing cargo/rustc build commands (or to attempt to run it by default).

[bergkvist]

It seems like rustup might actually revert this change (rust-lang/rustup#4211), so it might not be necessary to do anything here

[bergkvist]

Closing now that rustup 1.28.1 has rolled back to the old behaviour: https://blog.rust-lang.org/2025/03/04/Rustup-1.28.1.html