Overlay with overridden fetchurl to access resources

[TakodaS]

@tejing

(pkgs.extend (final: prev: {
  fetchurl = args: (prev.fetchurl.override {
    inherit (pkgs) cacert;
  }) (args // { netrcPhase = "foobar"; });
})).fetchurl {
  url="https://example.com/foo";
}

Following your example, I came up with the following:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs";
  };

  outputs =
    inputs:
    let
      system = "x86_64-linux";
      pkgsOld = (inputs.nixpkgs.legacyPackages.${system});
      overlay = final: prev: {
        fetchurl =
          args:
          (prev.fetchurl.override {
            inherit (pkgsOld) cacert;
          })
            (
              args
              // {

                netrcPhase = ''
                  cat > netrc <<EOF
                  machine foobar
                          login FOO
                          password BAR
                  EOF
                '';
              }
            );
      };
      pkgs = (inputs.nixpkgs.legacyPackages.${system}.extend overlay);
    in
    {
      packages.${system}.default = pkgs.fetchurl {
        url = "https://github.com/developit/unfetch/archive/refs/tags/isomorphic-4.0.2.tar.gz";
        hash = "sha256-Qwp5O4055CoHFx+ifJE0gcVlfeHyrg0H4Isp6XC0pkk=";
      };

    };
}

which avoids the infrec error. TYSM!