`ghcup install` sets default to installed version even without `--set` on command line

[0cjs]

When I install a program without using the --set option, GHCup still sets the default to that program, overriding any previous setting.

$ ghcup --version
The GHCup Haskell installer, version 0.1.50.2
c$ ll .ghcup/bin/
total 119M
-rwxr-x--- 1 cjs cjs 30M Jul  9 05:16 ghcup
lrwxrwxrwx 1 cjs cjs  11 Jul  9 05:16 stack -> stack-3.7.1
-rwxr-xr-x 1 cjs cjs 90M Jul  9 05:16 stack-3.7.1
c$ ghcup install cabal latest
...
[ Info  ] Installing cabal
[ Info  ] Cabal installation successful
c$ ll .ghcup/bin/
total 156M
lrwxrwxrwx 1 cjs cjs  14 Jul  9 05:18 cabal -> cabal-3.14.2.0
-rwxr-xr-x 1 cjs cjs 38M Jul  9 05:18 cabal-3.14.2.0
-rwxr-x--- 1 cjs cjs 30M Jul  9 05:16 ghcup
lrwxrwxrwx 1 cjs cjs  11 Jul  9 05:16 stack -> stack-3.7.1
-rwxr-xr-x 1 cjs cjs 90M Jul  9 05:16 stack-3.7.1
c$ ghcup install cabal recommended
...
[ Info  ] Installing cabal
[ Info  ] Cabal installation successful
c$ ll .ghcup/bin/
total 192M
lrwxrwxrwx 1 cjs cjs  14 Jul  9 05:18 cabal -> cabal-3.12.1.0
-rwxr-xr-x 1 cjs cjs 36M Jul  9 05:18 cabal-3.12.1.0
-rwxr-xr-x 1 cjs cjs 38M Jul  9 05:18 cabal-3.14.2.0
-rwxr-x--- 1 cjs cjs 30M Jul  9 05:16 ghcup
lrwxrwxrwx 1 cjs cjs  11 Jul  9 05:16 stack -> stack-3.7.1
-rwxr-xr-x 1 cjs cjs 90M Jul  9 05:16 stack-3.7.1

I've tested this with install stack as well, and gotten the same result.

This is rather dangerous, because I not only may find the version I happened to be using for a build quietly changing, but it could even change the version being used in the middle of a build running in another window.

I don't think it's relevant, but I have nothing related to "install" or "set" in my GHCup configuration file.

[dfordivam]

This is the default behavior of ghcup install for tools other than the ghc (ie cabal, stack and hls). I guess the assumption here is that the user would want to use the installed tool immediately. And changing the behavior of ghcup install would be a breaking change.

Note that it is possible to specify --no-set to achieve only installation.

[hasufell]

Yes, this is on purpose.

[0cjs]

Well, first of all that's just confusing: why should I have to remember (or even know) for each individual tool whether it's an auto-update tool or not. What are the criteria that determine this?

But also, this seems completely undocumented.

1. The help text is misleading; it says only --set Set as active version after install, neither indicating that sometimes you get --set behaviour without the --set flag, nor indicating that there's a --no-set flag.
2. There's no mention of this at all in the User Guide.

[hasufell]

What are the criteria that determine this?

That has been explained: there's rarely any use case for switching between cabal versions. The latest usually works for all projects. This is not the case for GHC.

But also, this seems completely undocumented.

PRs welcome.