I didn’t do Haskell in a while, since I do more mainstream languages at my professional work. The haskell tooling always confused me in the past, though, when cabal is the official package manager, but then everyone was using stack all of a sudden, the GHCup was useful. It was never easy to set up an environment as it is with dotnet or python for example.
But I read something that has let me hope: The deficiencies of cabal from the past concerning dependency hell seem to be fixed. The problem left is that an environment is needed to not clutter the operating system, since Haskell packages depend on native libraries, in general. And this is where guix comes into play.
Setting up guix
On ubuntu, in a terminal, type
> sudo apt update
> sudo apt install guix
> guix pullguix pull was important for me, since the initial installation provided version 1.3, that did not contain guix shell, but just the obsolete guix environment. guix pull takes a long time to complete.
It is possible to crate several profiles with guix, which can be retrieved by guix package --list-profiles, which certainly will prove useful (just to remember: guix package -i hello -p ~/.config/guix/haskell), but for now, I’ll stick with the so-called current profile, since I’m just experimenting, and it is possible to roll back all modifications that are done by guix.
Install cabal and GHC
To install cabal, I type guix install cabal-install, which can be found by first guix search cabal. I had to follow the recommendation in the command output to change the environment variables by
hint: Consider setting the necessary environment variables by running:
GUIX_PROFILE="/home/gary/.guix-profile"
. "$GUIX_PROFILE/etc/profile"and was able to verify with which cabal that the installation took place into a profile that did not have previously been showing up with guix package --list-profiles, but now does.
I’m realizing that I have an old version of the ghc compiler on my system, and it seems that I previously used ghcup to install it. I was not able to uninstall these package with apt. Great, this is why I need a better solution for haskell development! Let me just delete the folders ~/.ghc and ~/.ghcup (am I really doing this?!).
Now, I use cabal to create a new dummy haskell project and run it, by cabal run, which gives me the reminder that ghc is not available on my system. Thank you! So guix install ghc. And it works!
But wait, I’d have expected this to be installed by guix automatically. Maybe it wasn’t, since it was found on my path. To check that, let me try to roll back the installation of cabal and reinstall it. To rollback, the concept of generations is used. Any modification of the guix environment leads to a new generation.
> guix package --list-generations
Generation 1 Mär 08 2024 10:59:24
cabal-install 3.6.2.0 out /gnu/store/qwwhmz0g8nxq8sj181pd4vvfx64f3c1a-cabal-install-3.6.2.0
Generation 2 Mär 08 2024 11:17:09 (current)
+ ghc 9.2.5 out /gnu/store/m0rjzlphxl50xhsnh7sga6w4hpi0hs56-ghc-9.2.5Two roll backs bring me back to no packages anymore.
> guix package --roll-back
switched from generation 2 to 1
> guix package --roll-back
The following derivation will be built:
/gnu/store/s418j4p738i062m49nl0jafl1j52k2g4-profile.drv
building profile with 0 packages...
switched from generation 1 to 0
> guix package -IThe last command lists all packages, and it does not show any output, which is what is to be expected. Then, guix install cabal-install again does not install ghc, it doesn’t even download cabal-install but just switched back to generation 1. That’s efficient. So I tried guix package --roll-back again, followed by package garbage collection guix gc. Then guix install cabal-install actually downloaded a lot more stuff than in the initial try, but still, no ghc is available. I am not sure, if this is correct behavior, or if my environment settings may be not correct, yet (since I didn’t put anything into configuration files, such as .bash_profile or similar), but I am quite satisfied by this structured approach to package management, which is easy to understand.
Summary
That’s already it. It was much less of a headache than I was expecting. The next steps I’m going to investigate are using multiple profiles in guix and trying to utilize a way to reuse a base configuration across all environments. The base configuration should contain all standard tools, like editors and cli helpers. Could I even arbitrarily compose multiple base configurations? Let’s see.