How to integrate GHC API programs with Cabal February 8, 2017
GHC is not just a compiler: it is also a library, which provides a variety of functionality that anyone interested in doing any sort of analysis on Haskell source code. Haddock, hint and ghc-mod are all packages which use the GHC API.
One of the challenges for any program that wants to use the GHC API is integration with Cabal (and, transitively, cabal-install and Stack). The most obvious problem that, when building against packages installed by Cabal, GHC needs to be passed appropriate flags telling it which package databases and actual packages should be used. At this point, people tend to adopt some hacky strategy to get these flags, and hope for the best. For commonly used packages, this strategy will get the job done, but for the rare package that needs something extra–preprocessing, extra GHC flags, building C sources–it is unlikely that it will be handled correctly.