{ config, lib, pkgs, ... }@args:
with import <stockholm/lib>;
{
  nixpkgs.config.packageOverrides = pkgs: let

    # This callPackage will try to detect obsolete overrides.
    callPackage = path: args: let
      override = pkgs.callPackage path args;
      upstream = optionalAttrs (override ? "name")
        (pkgs.${(parseDrvName override.name).name} or {});
    in if upstream ? "name" &&
          override ? "name" &&
          compareVersions upstream.name override.name != -1
      then trace "Upstream `${upstream.name}' gets overridden by `${override.name}'." override
      else override;

  in {}
  // import ./builders.nix args
  // mapAttrs (_: flip callPackage {})
              (filterAttrs (_: dir: pathExists (dir + "/default.nix"))
                           (subdirsOf ./.))
  // {
    empty = pkgs.runCommand "empty-1.0.0" {} "mkdir $out";

    haskellPackages = pkgs.haskellPackages.override {
      overrides = self: super:
        mapAttrs (name: path: self.callPackage path {})
          (mapAttrs'
            (name: type:
              if hasSuffix ".nix" name
                then {
                  name = removeSuffix ".nix" name;
                  value = ./haskell-overrides + "/${name}";
                }
                else null)
            (builtins.readDir ./haskell-overrides));
    };

    ReaktorPlugins = callPackage ./Reaktor/plugins.nix {};

    buildbot = callPackage ./buildbot {};
    buildbot-full = callPackage ./buildbot {
      plugins = with pkgs.buildbot-plugins; [ www console-view waterfall-view ];
    };
    buildbot-worker = callPackage ./buildbot/worker.nix {};

    # https://github.com/proot-me/PRoot/issues/106
    proot = overrideDerivation pkgs.proot (oldAttrs: {
      patches = singleton (pkgs.fetchurl {
        url = https://github.com/openmole/PRoot/commit/10119a1f1fd7dea012464ae176c2b5fc3eb18928.diff;
        sha256 = "0cmd95mz8p5ifjvfvi4g9zzyxqddbscxin2j3a9zbmbjl2wi458g";
      });
    });

    # XXX symlinkJoin changed arguments somewhere around nixpkgs d541e0d
    symlinkJoin = { name, paths, ... }@args: let
      x = pkgs.symlinkJoin args;
    in if typeOf x != "lambda" then x else pkgs.symlinkJoin name paths;

    test = {
      infest-cac-centos7 = callPackage ./test/infest-cac-centos7 {};
    };
  };
}