haskell modules: Make 17.09 forwards compatible

[4e6]

Motivation for this change

Recent commit 8155312 introduced new buildHaskellPackages argument and broke compatibility with 17.09

Now if we call makePackageSet in 17.09 with the new argument it fails with called with unexpected argument ‘buildHaskellPackages’.

This PR adds an ellipsis (...) to prevent called with unexpected argument errors in the future:

error: anonymous function at /nix/store/bfbxsw3jma333xv6x4r2kglwwa3f9zx8-nixpkgs-channels-c1d9aff56e0ae52ee4705440fe09291a51e91977-src/pkgs/development/haskell-modules/make-package-set.nix:4:1 called with unexpected argument ‘buildHaskellPackages’, at /nix/store/bfbxsw3jma333xv6x4r2kglwwa3f9zx8-nixpkgs-channels-c1d9aff56e0ae52ee4705440fe09291a51e91977-src/lib/customisation.nix:74:12
(use ‘--show-trace’ to show detailed location information)

cc @Ericson2314

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[Ericson2314]

Uh shouldn't this be against 17.09?

[Ericson2314]

Also please add a comment on each ellipsis saying why. Otherwise looks good, thanks.

[dhess]

@Ericson2314 I think the point here is to make sure that you can use makePackageSet (edit without explicitly specifying the new parameter) with either 17.09 or a recent nixpkgs. Right now it's either-or because of the new parameter.

[Ericson2314]

@dhess yeah but to do that we need to allow passing the extra argument for both, and just have it be unused on, 17.09, so the extra unused parameter or ellipses (I actually prefer extra parameter, come to think of it, too) goes on 17.09.

[dhess]

@Ericson2314 OK, thanks for the clarification. (I am not the author but am eagerly awaiting the fix ;)

[Ericson2314]

NP. I'd do it myself but I'm on my phone.

[peti]

Please do not add ellipsis here. I don't want these functions to accept any random argument without an error.

[4e6]

ok, I'll use makePackgeSet instead

[peti]

I am sorry, but that is not what I meant. Please don't accept ... arguments at all. I don't want any of these functions to take random arguments without an error.

[4e6]

I added the comments. and addressed @peti remark

Ellipsis is added to create (some kind of) backward compatibility. With ellipsis, when argument list is extended in master, we can still support both master and release just by passing extra arguments.

[Ericson2314]

Yeah could you do buildHaskellPackages ? null instead?

[4e6]

Yeah could you do buildHaskellPackages ? null instead?

But it is a required argument, it should never be null. What's wrong with the ellipsis?

[Ericson2314]

@4e6 you missed me saying this PR should point at release-17.09 instead.

[Ericson2314]

I went ahead and changed the branch for you.

[peti]

Please accept specific arguments rather than using ....

You also need to rebase your PR relative to the current release-17.09 branch.

[4e6]

I didn't get that we are talking about merging into release-17.09. Then buildHaskellPackages ? null makes sense. Sorry for the noise.

[Ericson2314]

Looks great now. Thanks!

[Ericson2314]

Oops meant to squash, but it didn't do it. Oh well.