HLS not properly working when configuring XMonad

[reyniersbram]

Your environment

Which OS do you use?

• ArchLinux inside a virtual machine.

Which version of GHC do you use and how did you install it?

• 9.2.7 from stack

Which LSP client (editor/plugin) do you use?

• Neovim

Which version of HLS do you use and how did you install it?

• 1.10.0.0 from ghcup

Have you configured HLS in any way (especially: a hie.yaml file)?

• generated hie.yaml with gen-hie:

cradle:
    stack:
        - path: "xmonad/src"
          component: "xmonad:lib"

        - path: "xmonad/./Main.hs"
          component: "xmonad:exe:xmonad

        - path: "xmonad/tests"
          component: "xmonad:test:properties"

        - path: "xmonad-contrib/./"
          component: "xmonad-contrib:lib"

        - path: "xmonad-contrib/tests"
          component: "xmonad-contrib:test:tests"

        - path: "xmonad-contrib/."
          component: "xmonad-contrib:test:tests"

What's wrong?

I just started to try and use XMonad, but when editing xmonad.hs I get the following error:

I tried both with and without the generated hie.yaml file, without any difference. I tried to do some manual editing of this file as well, but since I didn't really have any idea what I was doing this didn't help either.

I did work on other Haskell projects before with the same neovim setup, but never came across this error.

This is my directory-structure, if this provides some extra usefull information:

The xmonad and xmonad-contrib directories are just the git repos.

Thanks in advance for the help!

[fendor]

Hi!

So, the thing is that xmonad.hs is a stand-alone haskell file. It does not belong to any project, and has no *.cabal or package.yaml file. As such, HLS does currently not know how to compile xmonad.hs.
Personally, I have never used xmonad, so I am wondering, what are you doing to make sure your xmonad.hs compiles successfully? Maybe we can go from there.

[reyniersbram]

I just use xmonad --recompile, I'm not sure how it then compiles to integrate with xmonad itself. I did some quick research to try and make a cabal file but without success.

[fendor]

I think a cabal file might still be your best course of action, although it will be slightly awkward. What did you try to write in the .cabal file? (Please, include the name you chose as well)

[reyniersbram]

I first initialized the project using stack (first message), but I tried again using cabal, so my directory looks a little bit different than in my first message:

The error message is still the same though.

My cabal files are:

cabal.project:

packages: */*.cabal

xmonad.cabal:

name:                  xmonad
cabal-version:    3.6.2.0

library
    hs-source-dirs: xmonad/src, xmonad-contrib/XMonad
    build-depends: base

These are the links to the xmonad and xmonad-contrib repositories:

• https://github.com/xmonad/xmonad
• https://github.com/xmonad/xmonad-contrib

[fendor]

ok, so, slight misunderstanding. xmonad and xmonad-contrib are already valid cabal packages. You include them in your project via the cabal.project file. I think, it'd be easiest to explicitly list the packages you use in your project, thus I recommend for cabal.project:

packages: ./ xmonad/*.cabal xmonad-contrib/*.cabal

While yours works probably fine, I prefer the explicit listing. So, in any way, your *.cabal file tries to add the sources from xmonad and xmonad-contrib to your package. That's not what you want, you want to depend on the packages xmonad and xmonad-contrib which you have included in your project via your cabal.project.

The xmonad.cabal, you should probably rename, because the package names will clash. I don't quite know what would be better, maybe xmonad-exe.cabal or something like that.
Then, you need to generate a .cabal file that successfully compiles xmonad.hs. So, you need a package description for that. To generate a good .cabal file, I start with cabal init --exe --non-interactive. The comments in there help a lot to understand what's going on.
We use an exe because I presume xmonad.hs contains a main. Otherwise, use --lib.
What you probably want is something like this:

cabal-version:      2.2
name:               xmonad-exe
version:            0.0.0
build-type:         Simple

executable xmonad-exe
  main-is:          xmonad.hs
  hs-source-dirs:   .
  ghc-options:      -Wall -rtsopts -threaded -with-rtsopts=-N
  build-depends:
    , base
    -- Note, this is how you add a dependency on the packages `xmonad` and `xmonad-contrib`
    , xmonad
    , xmonad-contrib 

  default-language: Haskell2010

Does this help you?

[reyniersbram]

Wow, that worked! Thank you very much!!
I didn't fully understand how .cabal files work but it makes sense now.
Thanks for your time!