The readFileType PR is ready to roll for anyone who has merge permissions.

Rebased, squashed, and ready for lift-off: https://github.com/NixOS/nix/pull/7447

{ nixpkgs ? builtins.getFlake "nixpkgs"
, system  ? builtins.currentSystem
, lib     ? nixpkgs.lib
, pkgsFor ? nixpkgs.legacyPackages.${system}
}: let
  keep   = _: v: ( builtins.tryEval ( lib.isDerivation v ) ).success;
  drvs   = lib.filterAttrs keep pkgsFor;
  names  = builtins.attrNames drvs;
  sdirN  = c: n: builtins.substring 0 c ( lib.toLower n );
  shards = c: builtins.groupBy ( sdirN c ) names;
  defPkg = name: {
    name = lib.toLower name;
    value."default.nix" = ''
      { system ? builtins.currentSystem }: let
        nixpkgs = builtins.getFlake "nixpkgs/${nixpkgs.rev}";
        pkgsFor = nixpkgs.legacyPackages.''${system};
      in pkgsFor."${name}"
    '';
  };
  mkShardDir = ns: builtins.listToAttrs ( map defPkg ns );
  self = {
    unit5 = builtins.mapAttrs ( _: mkShardDir ) ( shards 5 );
    unit4 = builtins.mapAttrs ( _: mkShardDir ) ( shards 4 );
    unit3 = builtins.mapAttrs ( _: mkShardDir ) ( shards 3 );
    unit2 = builtins.mapAttrs ( _: mkShardDir ) ( shards 2 );
    unit1 = builtins.mapAttrs ( _: mkShardDir ) ( shards 1 );
    unit  = self.unit4;
  };
in self

In reply to @infinisil:matrix.org
Sandro 🐧: Feel free to join, we'll take a look at https://github.com/nixpkgs-architecture/simple-package-paths/issues/30

In reply to @infinisil:matrix.org
Robert Hensing (roberth) tomberek John Ericson growpotkin ( Alex Ameen ): I opened some PR's and will likely open more, please review them this week so we can iterate asynchronously for the planned RFC next week, I recommend watching the entire repository: https://github.com/nixpkgs-architecture/simple-package-paths/pulls