Multi Cradle: No prefixes matched when editing Setup.hs

[k355l3r-5yndr0m3]

Your environment

Arch Linux
Cabal
Neovim (lsp-config)

Steps to reproduce

1. Create new project
2. Change build-type to Custom

build-type:         Custom
custom-setup
  setup-depends:
    base,
    Cabal

3. Create a Setup.hs file and build
4. Open Setup.hs

Expected behaviour

hls works seamlessly on Setup.hs

Actual behaviour

hls output this error

Multi Cradle: No prefixes matched
pwd: /home/cha0s/testing
filepath: /home/cha0s/testing/Setup.hs
prefixes:
("app/Main.hs",Cabal {component = Just "testing:exe:testing"})

Debug information

I found this reddit post describing something similar but Stack is used instead.
The custom build script Setup.hs is the only file affected, the other seems to work fine.

[fendor]

Hi!

Unfortunately, this is simply not supported at this time. Here is an issue for the underlying hie-bios issue: haskell/hie-bios#208

[k355l3r-5yndr0m3]

That's a bit disappointing, but I've managed to figure out a temporary solution. Adding an hie.yaml file with the following content.

cradle:
  cabal:

will change the error into something like this.

   Error: cabal: Failed extracting script block: `{- cabal:` start marker not
   found

Inserting the following lines at the top of the Setup.hs file will fix it and allow hls to function.

{- cabal: 
build-depends: base,
               Cabal
-}

If Setup.hs depends on other packages, you would need to add it both to the .cabal file and Setup.hs/

[fendor]

I did not know this was possible. Thank you very much for this workaround :)

[fendor]

Closing in favour of #3735 which also documents this workaround