Nixpkgs: Improve handling of rubbish in ghcWithPackages

[nh2]

Issue description

When you pass something bogus into ghcWithPackages, it succeeds instead of failing loudly.

Steps to reproduce

Write

nix-build --expr 'with import ./. {}; with import ./pkgs/development/haskell-modules/lib.nix { inherit pkgs lib; }; haskellPackages.ghcWithPackages (pkgs: with pkgs; [ dontCheck consul-haskell ])'

Debug an hour why it doesn't work (it builds the package with tests, ignoring dontCheck).

Realise that [ dontCheck consul-haskell ] should have been [ (dontCheck consul-haskell) ].

---

From @cleverca22

i would also expect ghcWithPackages to fail hard, because you gave it a lambda when it was expecting a string/package
so i'm surprised it even tried to build it

[clever@amd-nixos:~/apps/nixpkgs]$ nix-repl .
Welcome to Nix version 1.11.14. Type :? for help.

Loading '.'...
Added 7948 variables.

nix-repl> builtins.unsafeGetAttrPos "dontCheck" haskell.lib
{ column = 3; file = "/home/clever/apps/nixpkgs/pkgs/development/haskell-modules/lib.nix"; line = 24; }

nix-repl> builtins.unsafeGetAttrPos "ghcWithPackages" haskellPackages
{ column = 5; file = "/home/clever/apps/nixpkgs/pkgs/development/haskell-modules/make-package-set.nix"; line = 164; }

pkgs/development/haskell-modules/with-packages-wrapper.nix

paths = lib.filter (x: x ? isHaskellLibrary) (lib.closePropagation packages);

aha

nix-repl> haskellPackages.consul-haskell.isHaskellLibrary
true

if you give ghcWithPackages anything that lacks a .isHaskellLibrary attribute, it will silently filter it out of the package list

---

Technical details

• Nixpkgs version: dea58ce228e6f9686773745024eb844d8dc39fc3

[nh2]

CC @cleverca22 @peti -- Ideally we could make it fail loudly on such errors.

[peti]

Yeah, that's a good point. I suppose we could throw an error if any non-Haskell packages are included in the package list.

[domenkozar]

Filtering non-Haskell packages is a bit too agressive, one might have developer tools installed around.

I suggest we assert on non-derivations to catch errors like this.

[stale[bot]]

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