[Nix-dev] Developing Haskell packages that use the FFI

[James Cook]

> I’m working on a package that depends on the hs-mesos cabal package, but I’m
> ending up with the wrong version of the C++ protobuf library (incompatible
> headers) due to Nix somehow automatically picking up the wrong protobuf
> dependency for using the mesos C++ headers. How can I configure what version
> of protobuf is used for mesos / hs-mesos?

I don't know much about Haskell in nixpkgs, but it looks like this
probably comes from the "inherit (pkgs) protobuf" in the hs-mesos
expression in development/haskell-modules/hackage-packages.nix.  Maybe
replace that with "protobuf = pkgs.theProtobufVersionYouWant".