Instructions for Hello World

[davidspies]

There seem to be a ten different versions of everything and just picking the latest never works. There's no clarity or documentation anywhere on which pieces are needed in order to get a working "Hello World" project, using either stack or cabal. I'm reporting this as an HLS issue because just picking the latest of everything besides HLS does seem to work if I don't care about editor integration.

Your environment

Which OS do you use?

Ubuntu 24.04

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

I've been jumping between the various versions in ghcup tui trying them out one-by-one.
The latest one I see here is 9.12.1.
9.10.1 is the closest I've gotten to everything working.

How is your project built (alternative: link to the project)?
I tried both cabal init and stack new.

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

VSCode with no settings modifications whatsoever

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

The latest one available from ghcup tui: 2.9.0.1

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

No

What's wrong?

It takes excessive trial and error to find a combination of versions for tooling (ghc, hls, stack or cabal) where vscode doesn't complain and when vscode does complain, it gives no hints whatsoever as to how to fix it. There are no instructions anywhere for creating a new project which just works on opening vscode. Here's what I get when I use the latest of everything:

Even when I do manage to get the right combination of versions, I get this error when trying to autoformat:

I tried switching to stack and browsing a bit and eventually figured out it wanted me to use ghc 9.8.4 so I switched to that version. But now when I open vscode I see this error:

Any help figuring out the right version combination would be much appreciated

[fendor]

Hi, thank you for the bug report!

The HLS docs show which GHC version HLS is currently supporting: https://haskell-language-server.readthedocs.io/en/stable/support/ghc-version-support.html

Also, following the ghcup recommendation should also always work, so ghc-9.4.8 and latest HLS according to:

See the recommended tags.

That should give you a working installation.

Regarding the second error, you seem to be running into this issue: haskell/cabal#10457
We are trying to sync that up, but essentially using the interactive cabal init (cabal init -i) mode should give you a good default project.

The last HLS release was some time ago, which is very unfortunate as we don't support the 9.12.1 GHC releases yet

[fendor]

Looking at your examples in detail, it seems like you are actually trying to manage your HLS installations yourself in VSCode? This might be the reason why everything is crashing.

The preferred way is to let GHCup handle that for you. On your first extension startup, VSCode asks you what you want to do, whether you want to use PATH or GHCup, you might have missed this option, making VSCode default to PATH.
To remedy this situation, go to Settings > Haskell : ManageHLS and select GHCup.

[davidspies]

@fendor Thanks, I tried changing that (to Manage HLS installations with GHCup) and now when I create a fresh stack project I see this:

[davidspies]

I tried setting all the "recommended" versions in ghcup tui instead of all the latest versions, in particular including ghc-9.4.8. Then I created a new stack project, went into my stack.yaml and changed the snapshot to ghc-9.4.8 to line up with that choice. Now autoformat or ctrl-mouseover don't seem to do anything except cause it to get stuck "processing":

Are you actually not finding any of these issues reproduceable? I'm pretty sure I cleared out any relevant custom settings I had. I don't have any dependencies or custom changes to anything, I'm just using stack new.

---

ETA: Actually it works fine if I only open Lib.rs. I actually even managed to autoformat once. The "Processing" thing happens as soon as I then also open Main.rs and ctrl+mouseover someFunc

[fendor]

Well, your initial issues were caused by improper setup, of course I have a hard time to reproduce :) However, we did find it!

Stack support does have a couple of issues in HLS, see https://github.com/haskell/haskell-language-server/issues?q=is%3Aissue%20state%3Aopen%20label%3A%22build%20tool%3A%20stack%22 for an overview.

The issue you describe sounds familiar to me, it might be #366. To fix it, you have to run stack build in your terminal successfully before running the editor.

Currently, you often have an easier time using cabal.