Both the HLS project and the Stack project are keen that HLS support Stack and that Stack can output the information that HLS needs to support Stack (so that HLS does not depend on ‘hacks’). There is an open issue on Stack’s repository in that regard. From my perspective (Stack’s), what I am missing to help - and need to chase - is a precise specification of the information HLS needs that Stack can provide and in what format. I think HLS needs what is ultimately passed to GHC, but Stack does not know that directly - as Stack builds using Cabal (the library), not directly with GHC.