Sorry it was a bit late when I wrote that last night so it was unclear.

stack is using GHC  8.10.7 while Haskell Language Server seems to be using GHC 9.4.4. At various points while using VS Code I've gotten popups like "HLS is unable to determine GHC version" but later those stopped happening.

Is this a problem that they are using different versions? Would this explain why HLS thinks mtl is hidden even though it's exposed in my cabal file?

Mike

On Sat, Jan 7, 2023 at 5:40 AM Dennis Raddle <dennis.raddle@gmail.com> wrote:

I'm opening the project by running VS Code first, then opening the root folder of the project. I don't have a 'code' command installed or no path to it set; this doesn't happen by default on MacOS but I could look it up.

But I think I got a better clue by running haskell-language-server-wrapper:

I got this line.

Run entered for haskell-language-server-wrapper(haskell-language-server-wrapper) Version 1.9.0.0 x86_64 ghc-9.4.4

And then:

Tool versions found on the $PATH
cabal:          3.6.2.0
stack:          2.3.3
ghc:            8.10.7

My stack.yaml is using the resolver

lts-18.19

which does specify GHC 8.10.7 according to what I looked up.

But that ghc-9.4.4 seems to be a problem.

Thanks! But how to fix?

On Sat, Jan 7, 2023 at 5:13 AM Fendor <power.walross@gmail.com> wrote:

How are you launching VSCode? Make sure you open the root of the project in VSCode.
Opening VSCode from the cli via `code .` when you are in the correct directory is the most reliable.

Further, on the cli, try running HLS like this: `haskell-language-server-wrapper --debug <some-path-to-a-source-file>` from the root of your project.
Does this report the same error? If yes, more info about the project is needed like the .cabal file and the logs. Otherwise, it is a problem with the editor (e.g., PATH variable shenanigans).

Best regards,
Fendor

On 07/01/2023 10:00, Dennis Raddle wrote:

I'm trying to get HLS set up with a stack project on VS Code. I'm getting messages like this:

Could not load module ‘Control.Monad.Except’
It is a member of the hidden package ‘mtl-2.2.2’.
You can run ‘:set -package mtl’ to expose it.
(Note: this unloads all the modules in the current scope.)

But these are in the "Problems" tab of VS Code (and show as red underlines).

When I run stack clean, stack build I don't see any error like this at all.

And yes, I made sure mtl was added everywhere in cac.cabal. (I'm using cac.cabal not stack.yaml... is that my problem?)

I tried stack clean; stack build; restart HLS several times.

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