"Couldn't load cradle for ghc libdir"

Question

I'm trying to setup haskell-language-server with VS Code. My project is setup differently from most haskell projects, wherein the workspace root (project root) does NOT contain a haskell project. Instead, the haskell project is in a haskell/ subdir.

• I've generated hie.yaml using implicit-hie and placed it in the haskell/ subdir

• I've configured VS Code to start HLS with an extra --cwd /workspace/haskell argument (which seems to be getting respected, at least partly, as can be seen from the HLS logs below).

• Problem: I constantly keep getting an error notification in VS Code which corresponds to the following error in the HLS log. If you notice, the ghc --print-libdir command seems be running in the /workspace directory and not the expected /workspace/haskell directory.

  Couldn't load cradle for ghc libdir.
    Cradle error: CradleError {cradleErrorDependencies = [], cradleErrorExitCode = ExitSuccess, cradleErrorStderr = ["Couldn't execute ghc --print-libdir"]}
    Root dir path: /workspace
    hie.yaml path: 
    Cradle: Cradle {cradleRootDir = "/workspace", cradleOptsProg = CradleAction: Default}
  

Question

How do I tell VSCode and HLS to treat /workspace/haskell as the root dir for all haskell related stuff even if the project root is /workspace?

Complete HLS Logs

2022-12-25T05:12:06.214364Z | Info | haskell-language-server version: 1.8.0.0 (GHC: 8.10.7) (PATH: /home/vl/.ghcup/hls/1.8.0.0/lib/haskell-language-server-1.8.0.0/bin/haskell-language-server-8.10.7)
2022-12-25T05:12:06.214846Z | Info | Directory: /workspace/haskell
2022-12-25T05:12:06.214935Z | Info | Starting (haskell-language-server) LSP server...
  GhcideArguments {argsCommand = LSP, argsCwd = Just "/workspace/haskell", argsShakeProfiling = Nothing, argsTesting = False, argsExamplePlugin = False, argsDebugOn = False, argsLogFile = Just "/tmp/hls.log", argsThreads = 0, argsProjectGhcVersion = False}
  PluginIds: [ pragmas
             , LSPRecorderCallback
             , rename
             , ghcide-completions
             , stan
             , class
             , refineImports
             , splice
             , changeTypeSignature
             , qualifyImportedNames
             , alternateNumberFormat
             , hlint
             , ghcide-code-actions-fill-holes
             , floskell
             , ghcide-extend-import-action
             , codeRange
             , haddockComments
             , importLens
             , retrie
             , ghcide-type-lenses
             , ghcide-code-actions-imports-exports
             , ghcide-hover-and-symbols
             , eval
             , gadt
             , fourmolu
             , tactics
             , callHierarchy
             , stylish-haskell
             , ghcide-code-actions-type-signatures
             , ghcide-code-actions-bindings
             , moduleName
             , brittany
             , ormolu
             , ghcide-core
             , explicitFixity ]
2022-12-25T05:12:06.215151Z | Info | Logging heap statistics every 60.00s
2022-12-25T05:12:06.221240Z | Info | Starting LSP server...
  If you are seeing this in a terminal, you probably should have run WITHOUT the --lsp option!
  PluginIds: [ pragmas
             , LSPRecorderCallback
             , rename
             , ghcide-completions
             , stan
             , class
             , refineImports
             , splice
             , changeTypeSignature
             , qualifyImportedNames
             , alternateNumberFormat
             , hlint
             , ghcide-code-actions-fill-holes
             , floskell
             , ghcide-extend-import-action
             , codeRange
             , haddockComments
             , importLens
             , retrie
             , ghcide-type-lenses
             , ghcide-code-actions-imports-exports
             , ghcide-hover-and-symbols
             , eval
             , gadt
             , fourmolu
             , tactics
             , callHierarchy
             , stylish-haskell
             , ghcide-code-actions-type-signatures
             , ghcide-code-actions-bindings
             , moduleName
             , brittany
             , ormolu
             , ghcide-core
             , explicitFixity ]
2022-12-25T05:12:06.221718Z | Info | Starting server
2022-12-25T05:12:06.225754Z | Info | Started LSP server in 0.00s
2022-12-25T05:12:06.236359Z | Error | Couldn't load cradle for ghc libdir.
  Cradle error: CradleError {cradleErrorDependencies = [], cradleErrorExitCode = ExitSuccess, cradleErrorStderr = ["Couldn't execute ghc --print-libdir"]}
  Root dir path: /workspace
  hie.yaml path: 
  Cradle: Cradle {cradleRootDir = "/workspace", cradleOptsProg = CradleAction: Default}
2022-12-25T05:12:06.237070Z | Info | Registering IDE configuration: IdeConfiguration {workspaceFolders = fromList [NormalizedUri (-8339013940570246676) "file:///workspace"], clientSettings = hashed Nothing}
2022-12-25T05:12:06.256433Z | Info | Cradle path: haskell/src/Zoho/Analytics/BulkExport.hs
2022-12-25T05:12:25.869646Z | Info | Interface files cache directory: /home/vl/.cache/ghcide/main-e4b29176c5ce8651801b1fc09f3342a61bd37769
2022-12-25T05:12:25.870602Z | Info | Making new HscEnv. In-place unit ids: [main]
2022-12-25T05:13:06.235006Z | Info | Live bytes: 1413.69MB Heap size: 2639.27MB
2022-12-25T05:14:06.279529Z | Info | Live bytes: 1413.69MB Heap size: 2639.27MB
2022-12-25T05:15:06.336801Z | Info | Live bytes: 1413.69MB Heap size: 2639.27MB

Answer 1

Have you tried using a cabal.project file in your workspace folder? In it you could put something like

packages: haskell

which would specify haskell as a subdirectory that is a Haskell package. In this manner you may also specify multiple Haskell packages as part of a single Haskell project. See https://cabal.readthedocs.io/en/3.8/cabal-project.html#specifying-the-local-packages for documentation. (This may not be the right use of the option but see if it works.)