Confusing dialog on startup: "Need to download ghc-null"

[mduerig]

Your environment

Which OS do you use: Linux 5.4.0-109-generic 18.04.1-Ubuntu

Steps to reproduce

Add the following configuration and start VSCode:

    "haskell.toolchain": {
        "hls": "1.6.1.0",
        "ghc": null,
        "cabal": null,
        "stack": null
    }

Expected behaviour

VSCode starts and is ready to use, not displaying "strange" dialogue boxes.

Actual behaviour

VSCode starts and a dialogue pops up "Need to download ghc-null, continue?"

After confirming with "Yes", everything works normal.

[fendor]

Hi, thank you for your bug report!

Do you have GHC installed on your system? If yes, how and which GHC version?

[mduerig]

No, I don't have it installed globally. This happens with pure stack projects.

[mduerig]

FWIW, I just installed 8.10.7 (via ghcup). This makes the problem go away.

[fendor]

Awesome, thank you for the detailed bug report!

[hasufell]

Are you using ghc 9.0.2 with stack? Or why do you lock an older HLS version? There's a workaround for the bindist issue: haskell/haskell-language-server#2862 (comment)

[mduerig]

Are you using ghc 9.0.2 with stack?

Yes and it kept crashing HLS so I reverted to 1.6.1.0 for now. But this is not related to this issue as I'm getting the same behaviour ("Need to download ghc-null") also with "hls": "null",.