Add compiler-nix-name to cabalProject

[hamishmack]

Setting the compiler explicitly does not make it easy for cross
compilation to also choose the correct compiler when compiling
build tools for the build platform. Also it is easy to pass the
wrong compiler type. Specifying just the nix-name of the compiler
makes that less likely.

[angerman]

I guess we could try ghc.nix-name? Isn't that a passthrough? Unless someone feeds in a completey different ghc.

[hamishmack]

I guess we could try ghc.nix-name? Isn't that a passthrough? Unless someone feeds in a completey different ghc.

I worry someone might be using ghc = haskell-nix.compiler.ghc865.overrideAttrs {...} and it would break their code if cabalProject used buildPackages.haskell-nix.compiler."${ghc.nix-name}" instead.

Perhaps we should mention that they can use ghcOverride arg in the warning (to get rid of the warning)? But that still feels wrong, it might be better if they changed their code to add haskell-nix.compiler.X as an overlay and then used compiler-nix-name = "X";.

[angerman]

Agreed.