Nixpkgs: GHCJS failing to build on x86_64-linux

[dhruvio]

Describe the bug
Unable to build GHCJS on my x86_64-linux machine when building against the package set from NixOS/nixpkgs-channels 1d8018068278a717771e9ec4054dff1ebd3252b0. The GHCJS Nix definition is the same as HEAD on master.

To Reproduce
Steps to reproduce the behaviour:

# On an x86_64-linux machine:
nix-build -A haskell.compiler.ghcjs <path_to_nixpkgs>

Expected behaviour
Successfully builds GHCJS and creates result.

Actual behaviour
The build fails, and the following error is emitted to the terminal:

error: Package ‘ghcjs-8.6.0.1’ in /nix/store/a6wqbwdpls8b04ylz98b9cd8x9nww9h5-source/pkgs/development/compilers/ghcjs-ng/default.nix:66 is not supported on ‘x86_64-linux’, refusing to evaluate.

Notify maintainers
@ElvishJerricco

Metadata
Note that I am building GHCJS against NixOS/nixpkgs-channels commit: 1d8018068278a717771e9ec4054dff1ebd3252b0.

 - system: `"x86_64-linux"`
 - host os: `Linux 5.6.18, NixOS, 20.03.2611.bb8f0cc2279 (Markhor)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.6`
 - channels(root): `"nixos-20.03.2611.bb8f0cc2279"`
 - channels(dd): `"nixos-17.09-17.09.3269.14f9ee66e63"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[dhruvio]

Looks like this is the commit that results in this regression: https://github.com/NixOS/nixpkgs/commit/e037eb4046df34520780af723a33bee3ee15032d

cc @peti

[maralorn]

Well, the regression here happened much earlier, that commit only admitted it.

[cdepillabout]

@dhruvio I don't think any of the three of us that regularly maintain the Haskell infrastructure here in Nixpkgs uses GHCJS, so you may have to dig into this if you'd like it fixed.

Alternatively, you could try asking for help on the NixOS Discourse: https://discourse.nixos.org/

[dhruvio]

Thanks, @cdepillabout and @maralorn. I'm not as experienced with GHCJS, but will try looking into it.

[dhruvio]

Also wanted to share, when I try building haskell.compiler.ghcjs.overrideAttrs (old: { meta = {}; }) (to circumvent the broken and platforms config), nix-build simply outputs nothing and hangs. Not sure how to debug this; any help would be appreciated.

EDIT: Please ignore this comment, I left it running for a while and it eventually started building. I can now debug it.

[dhruvio]

So, I've figured out the problem, and managed to get ghcjs building locally. Going to submit a PR shortly.

[cdepillabout]

Closed by #96193.