"cannot find current revision for snap rustup" on 'rustup update'

[HarrisonHemstreet]

$ rustup update
internal error, please report: running "rustup" failed: cannot find current revision for snap rustup: readlink /snap/rustup/current: no such file or directory

I also deleted some rust files in an attempt to delete the Rust programming language in an attempt to later reinstall because the normal rustup self uninstall was not working

[rbtcollins]

I don't know snappy well enough - is there some command to query the system / interrogate what snappy thinks is the current status of the system ?

[kinnison]

The way that @HarrisonHemstreet has reported this suggests there's a number of problems at play.

The reported "cannot find current version for snap" is likely due to an incorrect attempt to uninstall the snap. snap uninstall rustup would have likely been the right way, though having damaged the /snap/... tree I'm not sure what the fix will be.

As for rustup self uninstall wouldn't work -- there's at least a pair of things we can do to improve matters.

The first would be to permit non-standard installers (snap, distro packages, etc) to somehow provide some input on how to uninstall (e.g. a string in /etc/rustup/settings.toml perhaps). That way rustup self uninstall could display that instead of simply saying that it doesn't know how.

The second would be that rustup self uninstall should definitely remove the toolchains before reporting the above message so that at minimum the user has cleaned up their ~/.cargo and ~/.rustup which is likely the most important thing they need rid of.

[rbtcollins]

See also #2662

[workingjubilee]

@rustbot label: +O-linux