Here's another way to install Sparrow 2.1.3 (the current version) on NixOS:

```

environment.systemPackages [

...

# Install Sparrow 2.1.3

(pkgs.callPackage (pkgs.fetchurl {

url = "https://gist.githubusercontent.com/emmanuelrosa/a6f3c5ca3977d933064129ae723cfac2/raw/896c10bbfbf1f650e54626229c74d294b829f680/sparrow.nix";

hash = "sha256-F7l9h7HPniXXm7dHL4IWmzzhMBHTcrYwieKnaxAyj+w=";

}) {})

];

```

The example above installs from a Gist I just created: https://gist.github.com/emmanuelrosa/a6f3c5ca3977d933064129ae723cfac2

It's the same code in the Nixpkgs PR (https://github.com/NixOS/nixpkgs/pull/380755) except packaged into a single file.