Add a facility to rustup to show how its variables are currently set.

[RodBurman]

Problem you are trying to solve

Currently there is (or I can find) no way to see how the "variables" in rustup are set. The rustup set command allows you to set them but it has no --list variant neither does rustup show have a --variables variant. To be slightly more explicit, rustup set help displays:

Alter rustup settings

Usage: rustup[EXE] set <COMMAND>

Commands:
  default-host      The triple used to identify toolchains when not specified
  profile           The default components installed with a toolchain
  auto-self-update  The rustup auto self update mode
  auto-install      The auto toolchain install mode
  help              Print this message or the help of the given subcommand(s)

Options:
  -h, --help  Print help

But I cannot display how default-host, profile, auto-self-update or auto-install are configured.

Solution you'd like

I have no preference as to whether this is a new variant of show or set or both or even some other solution. If we take Unix shell command set as the exemplar, then rustup set would show this rather than assuming "help" as it does now, but since that is a breaking change it may well not be the preferred solution.

Notes

I have discussed this on zulip and been advised to raise an issue.

[rami3l]

@RodBurman Thanks for reporting!

I do think your proposal of making rustup set default to printing what we have set is quite reasonable. Also we can have an explicit subcommand rustup set list to do the same thing to mirror rustup override which already has that.

Also, repurposing something that didn't work before for other purposes is not a breaking change AFAIK.

Context

Following the intuition from git it seems that rustup set foo without any value should print the current value, however it currently resets that value, not sure whether we should change that.

[RodBurman]

May be just me but set list does not feel like a nice way to do this, since it is not totally implausible that at some point we would add a command rustup set list=enable|disable or some such. Similarly I would not have added the option for a "naked" help command, given there is also -h and --help providing the same function, but too late (probably) to change that. So I'd go with and/or --list by preference. Having set X reply "X=" sounds good too, but again a change that alters, rather than just adds, behaviour so maybe a problem as @rami3l says.

[rami3l]

@RodBurman Thanks for sharing your ideas!

The rationale of help vs -h vs --help here is that we really want to support all options so users would to get basic help no matter which style they are used to in the past.

But apart from that I think it's quite unlikely to have configuration options named help or list so I believe we are pretty good here.

[djc]

Maybe we should have something that shows a nice terminal display of all configuration plus relevant environment variables etc?

[FranciscoTGouveia]

Maybe we should have something that shows a nice terminal display of all configuration plus relevant environment variables etc?

So, should the command to show the set variables and the RUSTUP_* environment variables be rustup set list?
What are your thoughts on something like rustup show variables?

[RodBurman]

While we are adding show commands I'd like a "show all" which shows all installed targets for all installed toolchains.