Create 'ghcup healthcheck' command

[hasufell]

Could check:

• can download metadata
• enough space available
• ~/.ghcup/ghc/<ver> directories are not empty or missing files
• for every ~/.ghcup/ghc/<ver> there is a ~/.ghcup/bin/ghc-<ver> symlink
• ~/.ghcup/hls/<ver> directories are not empty or missing files
• for every ~/.ghcup/hls/<ver> there is a ~/.ghcup/bin/haskell-language-server-wrapper-<ver> symlink
• all tools can execute <tool> --version

[arjunkathuria]

This seems like a good idea, would help with first-step debugging when something fails for the end-users.

how do you feel about calling this ghcup doctor ?

[hasufell]

healthcheck is the standard terminology for this kind of thing, so I wanna stick with that.

I think it's not that hard to implement.

[arjunkathuria]

Yea, seems like it should be straight-forward. Is that checklist at the top exhaustive ?

[hasufell]

It's a start

[arjunkathuria]

We'll build it in a way that adding more checks should be trivial later. I'll look into it when i get a chance.

[hasufell]

excellent!

[hasufell]

One other major use case for this is:

• if the user has added a custom release channel (e.g. https://github.com/haskell/ghcup-metadata/blob/develop/ghcup-prereleases-0.0.7.yaml), then we want to warn them if there's a newer one available. ..that means we'll simply have to try to fetch ghcup-prereleases-0.0.8.yaml and then warn the user