[Haskell-cafe] problems with "stack ghc"

I'm using Haskell stack in the normal way (i.e. "stack build", "stack exec") for most of my application. However, I also need to build files that aren't in the stack source tree. My stack source tree is at ~/stack/cac/src/ Let's say I want to build the program /Users/Dennis/test.hs. So far I have been using stack ghc --stack-yaml ~/stack/cac/stack.yaml -- --make /Users/Dennis/test.hs I am confused. I thought this was working until today. I made some modifications in various places, including to my cac.cabal (but NOT my stack.yaml) and I'm having a problem. The libraries that test.hs imports are not getting rebuilt when they change. Are they *supposed* to be rebuilt? Any ideas how to debug this? D