Multiple Home Packages for GHC

Haskell tooling has improved considerably over the last year. Haskell IDE Engine was able to build a user-base that is happy with the feature set. Moreover, competing projects have been created to explore different design spaces. With the rise of these tools, certain limitations became apparent in the GHC API. For example, it is complicated to propagate updates between dependent packages.

In this proposal, I intend to enable GHC and GHCi to work with multiple packages at once. Most importantly to the end user, this allows development of multiple packages in GHCi. There are other workflows which can benefit from such functionality, such as incremental compilation and Haskell Language Server.