`rustup show active-toolchain` should provide the toolchain path

[rami3l]

Problem you are trying to solve

Let me guess: you actually just want to get the active toolchain path with this snippet...

https://github.com/corrosion-rs/corrosion/blob/b88ec09915a6b12d1aaec7e451ecf0e41a831030/cmake/FindRust.cmake#L423-L428

... however you might have tried the following options and concluded that neither is satisfactory:

• rustup show active-toolchain. This seems like the most obvious option, however it is somehow not willing to give you the toolchain path...
• rustup toolchain list --verbose. This does give you the toolchain paths, but you have to manually deduce what the active toolchain is :|

corrosion-rs/corrosion#590 (comment)

Solution you'd like

rustup show active-toolchain should provide the toolchain path, or optionally with --verbose.

Notes

No response

[ChrisDenton]

I think maybe with --verbose would be better? I worry that people are parsing rustup show active-toolchain so changing it might break scripts, etc. Admittedly, if those scripts are just splitting on the first whitespace then it is less of an issue.

rustup toolchain list --verbose. This does give you the toolchain paths, but you have to manually deduce what the active toolchain is :|

Maybe that should indicate the active toolchain as well.

[rami3l]

rustup toolchain list --verbose. This does give you the toolchain paths, but you have to manually deduce what the active toolchain is :|

Maybe that should indicate the active toolchain as well.

@ChrisDenton That's a description of the pre-v1.28 behavior. It's been fixed now.

[rami3l]

I think maybe with --verbose would be better? I worry that people are parsing rustup show active-toolchain so changing it might break scripts, etc.

@ChrisDenton That compatibility, if it exists in the first place, is unfortunately already broken since #3225, so essentially this is a similar situation to #4045.