cabal: fix upload to hackage

[steve-chavez]

When doing:

cabal upload dist-newstyle/sdist/postgrest-7.0.1.tar.gz

The following error is shown:

Error: Invalid package

'ghc-options: -Wall -Werror' makes the package very easy to break with
future GHC versions because new GHC versions often add new warnings.
Use just 'ghc-options: -Wall' instead. Alternatively, if you want to
use this, make it conditional based on a Cabal configuration flag
(with 'manual: True' and 'default: False') and enable that flag
during development.

Put -Werror in a cabal flag to work around this restriction.

[steve-chavez]

@monacoremo How can I pass an arg to callCaball2nix?

With plain cabal it would be like:

cabal v2-build -f werror 

I'm guessing the last set here should be used, but not sure how.

For reference, see https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/haskell-modules/make-package-set.nix#L216.

[monacoremo]

@steve-chavez There is a callCabal2nixWithOptions, but I think in this case it would be best to use something like lib.appendConfigureFlag to pass a ghc flag.

So a quick fix would be something like:

drv =
  lib.appendConfigureFlag (pkgs.haskellPackages.callCabal2nix name src {}) "-ghc-option=-Werror";

Looking at this, I just found failOnAllWarnings. So the best solution probably is:

drv =
  lib.failOnAllWarnings (pkgs.haskellPackages.callCabal2nix name src {});

[steve-chavez]

@monacoremo Thanks!

I ended up using enableCabalFlag. I wanted to keep the cabal file as the source of truth. That way stack and nix would use the same ghc-options. Could be helpful in case we change something in the future.