gargoyle-postgresql-nix needs postgresql to compile

[GuillaumedeVolpiano]

Nix.hs calls pg_ctl, which is installed by postgresql, so postgresql should be added to the build-depends in cabal.

[alexfmpe]

Hey, I'm not sure what to do here.

build-depends is for haskell libraries, and I don't find a postgresql one, so I assume you mean the normal postgresql.
build-tools or build-tools-depends both seem to be for haskell executables, since that's what cabal knows how to package manage.

In this repo and in nixpkgs, postgresql seems to be manually added to the build environment in nix, outside of cabal

[GuillaumedeVolpiano]

Sorry, bad manners on my part, I should have proposed a PR at the same time.
Cabal has the pkgconfig-depends field for this. See #50
To be honest, I think this is a corner case, on which I only stumbled because I was looking at updating some gentoo-haskell packages, made a small blunder with a package and ended up reinstalling gargoyle-postgresql-nix in a sandbox with only its explicit dependencies while correcting my mistake (It's hidden somewhere in there gentoo-haskell/gentoo-haskell#1689)

Long story short: there is a cabal field for non-haskell dependencies (actually, two, you can also use extra-libraries), I'll let you decide whether you want to use it or not.

[alexfmpe]

Ah, now I understand.
I think this might also get rid of the override in nixpkgs as libraryPkgconfigDepends is auto-populated now.

$ cd gargoyle-postgresql-nix && cabal2nix .
(...)
  libraryPkgconfigDepends = [ libpq ];
(...)