lnl-overlay.nix

self: super:

{
  # Install overlay:
  # $ mkdir -p ~/.config/nixpkgs/overlays
  # $ curl https://gist.githubusercontent.com/LnL7/570349866bb69467d0caf5cb175faa74/raw/3f3d53fe8e8713ee321ee894ecf76edbcb0b3711/lnl-overlay.nix -o ~/.config/nixpkgs/overlays/lnl.nix
  userPackages = super.userPackages or {} // {

    # Example:
    hello = self.hello;
    # add more packages here...

    # Default packages:
    # cacert = self.cacert;
    # nix = self.nix;  # don't enable this on multi-user.

    nix-rebuild = super.writeScriptBin "nix-rebuild" ''
      #!${super.stdenv.shell}
      if ! command -v nix-env &>/dev/null; then
          echo "warning: nix-env was not found in PATH, add nix to userPackages" >&2
          PATH=${self.nix}/bin:$PATH
      fi
      exec nix-env -f '<nixpkgs>' -r -iA userPackages "$@"
    '';

  };
}

@lilyball I was trying with this, copied from your comment https://gist.github.com/LnL7/570349866bb69467d0caf5cb175faa74#gistcomment-3372828.

self: super:
# Packages exposed as part of nixpkgs.userPackages
{
  inherit (self)
    fish tmux
    # …
    ;
}

@Amir-Ahmad Oh I think you probably put this in ~/.config/nixpkgs/overlays/ directly, yes? I suppose I should have elaborated. Your directory structure should look like

~/.config/nixpkgs/overlays/
    userPackages/
        default.nix
        packages.nix

The nested folder name (userPackages above) doesn't matter, but the two files do need to be nested in a folder, and the main file is default.nix in this folder.

What this does is it makes userPackages/default.nix to be the actual overlay, and that in turn imports ./packages.nix to construct the userPackages set. By putting both files in the top level overlays folder you instead make them two separate overlays and the packages.nix file is then trying to overwrite each package with itself, which causes infinite recursion.

@lilyball It's working now! thanks for the explanation 👍