Expose GHC with packages

[deemp]

Sometimes, I need to write scripts that use Cabal and GHC with all necessary packages. At the same time, I don't want to run the script inside nix develop because I run it in CI and don't want to wait to get all dependencies from the devShell.

Example of the script:

https://github.com/deemp/lima/blob/3eb85c7099ffc46897181b7132666842c8aec8bf/flake.nix#L129-L135

The necessary GHC is present in the haskellProjects config. However, I can get this GHC and add it to the script dependencies only with a crutch:

https://github.com/deemp/lima/blob/3eb85c7099ffc46897181b7132666842c8aec8bf/flake.nix#L118-L122

Therefore, I suggest to add haskellProjects.ghc option that will provide the GHC unless devShell.enable = false.

[srid]

Do you mean exposing something like pkgs.haskellPackages.ghc.withPackages as config.haskellProjects.default.outputs.<??>?

PR welcome!

[deemp]

@srid yes. As I understand, you use shellFor which provides ghcWithPackages with all packages necessary to build the given haskell packages.

haskell-flake/nix/modules/project/devshell.nix

Line 125 in 28a0a79

if lib.hasAttr "extraDependencies" (lib.functionArgs finalPackages.shellFor) then

I'd like to have this ghcWithPackages exposed somewhere.

.outputs looks like a good place, yes.

[pmiddend]

I'm in favor of doing this. Right now I have no idea (at least from reading the docs) on how to change the GHC version used. But I need to test with different GHC versions from time to time.

Edit: Ah, just found out about basePackages to fix the situation.