ghcWithPackages fails for ghcjs-ng

[cocreature]

Issue description

Trying to enter a nix-shell using ghcWithPackages fails for the ghcjs-ng derivations (8.2 and 8.4) with errors like the following:

building '/nix/store/05qi9d7am25xpwgy8mk304npmqad18a0-ghcjs-8.4.0.1-with-packages.drv'...
There are problems in package dlist-0.8.0.4:
  dependency "base-4.11.1.0-5Kf3GqzZBK3J87Uu7pRIno" doesn't exist
  dependency "deepseq-1.4.3.0-42XnsAVec7XA2IheMXu1r7" doesn't exist

The following packages are broken, either because they have a problem
listed above, or because they depend on a broken package.
dlist-0.8.0.4

In this case I tried haskell.packages.ghcjs84.ghcWithPackages(pkgs: [pkgs.dlist]) but the issue seems to appear for all packages I tried (but it doesn’t happen if the list of packages is empty).

Steps to reproduce

Run the following command

nix-build -E 'with import (builtins.fetchTarball { url = "https://github.com/NixOS/nixpkgs/archive/3e3a9e661d7ef83f9dfc26d948a12f8ee1334f6d.tar.gz"; sha256 = "07rhxdig4l0xlpwdg4z0vsz4k3gvkd32bzi13mymv4mn9hbqwb4w"; }) {}; haskell.packages.ghcjs84.ghcWithPackages (pkgs: [pkgs.dlist])'

Technical details

• system: "x86_64-linux"
• host os: Linux 4.16.13-2-ARCH, Arch Linux, noversion
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.0.2
• channels(root): "nixpkgs-18.09pre140156.0e6fb50954b"
• channels(moritz): ""
• nixpkgs: /home/moritz/code/nixpkgs

[matthewbauer]

/cc @Ericson2314

[stepcut]

I believe this is happening because packages like deepseq and base are being installed in /libexec and dlist is being installed in /lib and the ghcWithPackages is only configuring things to look in one of those locations.

In my ignorant opinion I think the issue is that the core packages are also supposed to be in /lib not /libexec

[matthewbauer]

Can you confirm that #42191 fixes this for you?

[cocreature]

I can confirm that this fixes the error but ghcWithPackages still doesn’t behave correctly:

If I run nix-shell -p 'with import <nixpkgs> {}; haskell.packages.ghcjs84.ghcWithPackages (pkgs: [pkgs.dlist])' --command "ghcjs-pkg list" I don’t see dlist and if I try to compile a file that imports Data.DList in that shell using ghcjs I get an error about missing modules.

[stepcut]

I believe the reason you see that is that this patch gets ghcjs to see the base and deepseq libraries that are in /libexec but now ghcjs does not see the dlist library that is in /lib.

I can not explain why some libraries are in /libexec and others are in /lib. Under ghc and older ghcjs I believe all the libraries were in one single location.