HLS can't find Main.hs for Haskell default project in VS Code, despite being listed in .cabal, and goes into crash loop

[DavidMichaelRoberts]

Your environment

• Which OS do you use?

Mac OS 14.2.1 (23C71)

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

v9.4.8, pasting command from https://www.haskell.org/ghcup/

• How is your project built (alternative: link to the project)?

Unedited template Haskell project created via cabal init --interactive, the resulting .cabal file is below, minus metadata.

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

VS Code, pretty much a clean install

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

2.5.0.0, via VS Code

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

No

What's wrong?

I'm aware of #1297, but I'm not doing anything fancy at all.

Working with Cabal and a clean install of HLS and taking the template Haskell project, which does build, I'm getting the dreaded error

Loading the module '/Users/david/[SNIPPED]/app/Main.hs' failed.

It may not be listed in your .cabal file!
Perhaps you need to add `Main` to other-modules or exposed-modules.

For more information, visit: https://cabal.readthedocs.io/en/3.4/developing-packages.html#modules-included-in-the-package

Despite Main.hs being listed in my .cabal file, opening VS Code after successful compilation in the correct folder etc.

HLS was working earlier in the week, and even after it broke on a larger project, it still worked on the template project, and then the next day HLS was broken on the template project too. I did not do any major upgrades that I am aware of. The larger project was pulled clean from GitHub, and my colleague also pulled a clean copy and had it work fine, before I tried to debug, and found that not even the template project resulting in HLS working properly.

See the attached log, but the HLS specifically breaks when it tries to find info on a type (or similar) to display as a tooltip in VSCode.

Debug information

Here's what I think is relevant from the log: HLS_log.txt

My settings.json from VS Code is (this is the complete file)

{
    "haskell.manageHLS": "GHCup",
    "git.autofetch": true,
    "editor.formatOnSave": true,
    "files.hotExit": "off",
    "editor.fontFamily": "JetBrains Mono, Menlo, Monaco, 'Courier New', monospace",
    "editor.fontLigatures": true
}

The .cabal file of the project contains the following settings, after the project metadata (maintainer, license etc):

cabal-version:      3.0

-- SNIPPED METADATA

build-type:         Simple

extra-doc-files:    CHANGELOG.md

common warnings
    ghc-options: -Wall

executable situated-reasoner2
    import:           warnings
    main-is:          Main.hs

    -- Modules included in this executable, other than Main.
    -- other-modules:

    -- LANGUAGE extensions used by modules in this package.
    -- other-extensions:

    build-depends:    base ^>=4.17.2.1
    hs-source-dirs:   app
    default-language: Haskell2010

Cabal version is 3.10.2.1, Stack (though I'm not using it) is v2.13.1, and GHCup is v0.1.20.0, and I have run cabal update.

My PATH variable contains /Users/david/.cabal/bin:/Users/david/.ghcup/bin

[michaelpj]

Try adding the following hie.yaml:

cradle:
  cabal:

[DavidMichaelRoberts]

Did that, and the result is no different. Here's the end of the log:

2024-02-02T23:15:36.360178Z | Info | Starting server
2024-02-02T23:15:36.385373Z | Info | Started LSP server in 0.03s
2024-02-02T23:15:36.866594Z | Info | Registering IDE configuration: IdeConfiguration {workspaceFolders = fromList [NormalizedUri 7466103998142758901 "file:///Users/david/[SNIPPED]"], clientSettings = hashed Nothing}
2024-02-02T23:15:36.881661Z | Info | Cradle path: src/SVA/SValuation.hs
2024-02-02T23:15:36.882082Z | Info | invoking build tool to determine build flags (this may take some time depending on the cache)
2024-02-02T23:15:37.327524Z | Warning | No plugin handles this "textDocument/semanticTokens/full" request.
[Error - 09:45:37] Request textDocument/semanticTokens/full failed.
  Message: No plugins are available to handle this SMethod_TextDocumentSemanticTokensFull request.
 Plugins installed for this method, but not available to handle this request are:
semanticTokens is disabled globally in your config.
  Code: -32601 
2024-02-02T23:15:37.745070Z | Info | cabal --builddir=/Users/david/.cache/hie-bios/dist-[SNIPPED]-bd3c78c81bf13db646dfcdd1d2c74c8a v2-repl --with-compiler /Users/david/.cache/hie-bios/wrapper-b54f81dea4c0e6d1626911c526bc4e36 --with-hc-pkg /Users/david/.cache/hie-bios/ghc-pkg-9d846c81c4c61505d0e53ee3963ccf4a /Users/david/[SNIPPED]/src/SVA/SValuation.hs
  Environment Variables
    HIE_BIOS_OUTPUT: /private/var/folders/99/4c53g77s3qv2h_53rv940bym0000gn/T/HIE_BIOS_OUTPUT2595-0
    HIE_BIOS_GHC: /Users/david/.ghcup/ghc/9.4.8/lib/ghc-9.4.8/bin/ghc-9.4.8
    HIE_BIOS_GHC_ARGS: -B/Users/david/.ghcup/ghc/9.4.8/lib/ghc-9.4.8/lib
[Error - 09:45:37] Request textDocument/codeLens failed.
  Message: eval: Rule Failed: GetEvalComments
  Code: -32803 
[Error - 09:45:37] Request textDocument/foldingRange failed.
  Message: codeRange: Rule Failed: GetCodeRange
  Code: -32803 

Let me know if you need more from before this.

[DavidMichaelRoberts]

Someone advised me that "template Haskell" is a separate thing, and certainly not what I'm working with! Reworded the title to be less misleading, I hope

[DavidMichaelRoberts]

For what it's worth, in a fresh account on this laptop, a fresh install of VSCode, CHCup and HLS works ok. Still don't know why it's not working in my current account. Could there be some kind of system environment variable that's messing things up?

[jhrcek]

In cases like this when things stop working mysteriously, I usually just delete hls's cache folder (where hls stores build artifacts). It's usually stored under home directory ~/.cache/ghcide - just rm -rf the whole directory
and restart hls (ctrl+shift+p - restart haskell language server)
Refer to https://haskell-language-server.readthedocs.io/en/latest/troubleshooting.html#clearing-hls-s-build-cache

[DavidMichaelRoberts]

Sadly, this didn't help.

[jhrcek]

Sorry, I'm out of my depth :-/
It seems to me that to make these kinds of issues easier to troubleshoot we should include more info in the error message than just Message: codeRange: Rule Failed: GetCodeRange

[DavidMichaelRoberts]

And now, mysteriously, the problem seems to have fixed itself. I really don't know what happened there!

[LucianU]

I suggest closing this issue since the problem can't be reproduced any longer. It can be reopened, in case it reappears.

[DavidMichaelRoberts]

@LucianU will do.

[mozhewen]

I suggest closing this issue since the problem can't be reproduced any longer. It can be reopened, in case it reappears.

No, it's not an issue that can't be reproduced. I ran into this issue with HLS2.9.0.1 + GHC9.10.1 + cabal3.10.3.0. For me, the problem was solved simply by copying the entire package folder into another directory. And after that, I found that the original path of my package contains a space in the parent folder just like: ~/foo bar/MyLib/. If I rename it to ~/foo_bar/MyLib/, problem solved.

So the true cause of the error message @DavidMichaelRoberts may be that [SNIPPED] contains some characters that HLS doesn't recognize, even a space. If this is the case, it's definitely a bug of HLS which can be fixed easily.

Hope this helps.

[fendor]

The issue you describe is a cabal bug iirc haskell/cabal#8875

So that should be solved with 3.12.

[DavidMichaelRoberts]

@mozhewen excellent, this fixed the problem. The errors came back after apparently fixing themselves as I noted above, and this suggested helped --- there was indeed a folder in the path with a space in its name.