[Nix-dev] Use of GHC's environment variable GHC_PACKAGE_PATH is incompatible with Cabal. Use the flag --package-db to specify a package database (it can be used multiple times)

[Mateusz Kowalczyk]

Hi,

I'd like to know the solution to the error message in the subject. I
have encountered it in the past if inside a Haskell project I did
something like

nix-shell --pure
eval "$configurePhase" && eval "$buildPhase" && eval "$checkPhase"

While this bothered me, the workaround was to exit and re-enter the
shell after buildPhase and run checkPhase then.

But now I want to actually test a package that this happens in on my
local Hydra and when it goes to run the test-suite, I get precisely that
message.

The package in question is Haddock here which is set to ‘doCheck =
false’ in nixpkgs even though I personally happen to know that the tests
do pass when actually ran. Not running the test-suite is obviously not
acceptable when you're the package maintainer…

Any ideas?

-- 
Mateusz K.