NIX_GHC_DOCDIR not set properly

[GuillaumeDesforges]

Describe the bug
When creating a Haskell development environment like this:

# shell.nix
{ pkgs ? import <nixpkgs> { } }:

let
  all-hies = import (fetchTarball "https://github.com/infinisil/all-hies/tarball/master") {};
  hie = all-hies.selection { selector = p: { inherit (p) ghc865; }; };

in
  pkgs.haskellPackages.shellFor {
    buildInputs = with pkgs; [
      hie
      cabal-install
    ];

    packages = (hp: with hp; [ gloss ]);
    withHoogle = true;
  }

with withHoogle = true, the doc is generated in ${ghcEnv}/share/doc/hoogle/html, however the NIX_GHC_DOCDIR is set to ${ghcEnv}/share/doc/ghc/html.
The former does not even exist (no such file or directory error on ls $NIX_GHC_DOCDIR).

See this line:

nixpkgs/pkgs/development/haskell-modules/make-package-set.nix

Line 322 in ff88224

"NIX_${ghcCommandCaps}_DOCDIR" = "${ghcEnv}/share/doc/ghc/html";

Note that I have seen #20730 and think that it is a different issue.

This issue prevents from using HIE in a nix-shell. See https://discourse.nixos.org/t/cant-make-hie-work-on-vs-code-with-nix/5277/

To Reproduce
Use previous shell.nix

nix-shell --run "ls $NIX_GHC_DOCDIR"
nix-shell --run "whateverfolderghcisin/share/doc/hoogle"

Expected behavior
nix-shell --run "ls $NIX_GHC_DOCDIR" should point to ${ghcEnv}/share/doc/hoogle/html

Metadata

% nix run nixpkgs.nix-info -c nix-info -m                                                                                                                                                                                                  ~
 - system: `"x86_64-linux"`
 - host os: `Linux 4.19.91, NixOS, 19.09.1686.69ed29f5f41 (Loris)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3`
 - channels(arsleust): `"home-manager"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:

[matthewbauer]

I think #76842 fixes this.

[snawaz]

And while we fix this, I hope we also set another variable HIE_HOOGLE_DATABASE to ${ghcEnv}/share/doc/hoogle/default.hoo (as required by haskell-ide-engine so that it works out of the box without any user settings.

[stale]

I marked this as stale due to inactivity. → More info

[sternenseemann]

Is there a need for HIE_HOOGLE_DATABASE or similar today with HLS? cc @maralorn.

[maralorn]

HLS has no hoogle support, yet.