How to download from url while packaging for nixpkgs?

I am trying to package Pharo for NixOS and, to do so, I need to download the sources of the VM to build them. However, for bootstrapping issues, the sources alone are not enough (unless you already have a Pharo VM available) to build the VM. For this reason, Pharo also publishes an archive containing both the source code and some additional artifacts that make bootstrapping possible. Thus, in my package, I fetch them with

pharo-sources = fetchurl {
    url =;
    sha256 = "08d04f6jc8kiwkx18ffig7wbjalqfryicxaw3am3kjsxsn2v19cb";

Then I opened a PR, and one of the automated checks fails with

error: URL literals are disabled

at /var/lib/ofborg/checkout/repo/38dca4e3aa6bca43ea96d2fcc04e8229/mr-est/ofborg-evaluator-2/pkgs/development/pharo/default.nix:22:11:

  21|     # also contains artifacts necessary for the bootstrapping.
  22|     url =;
    |           ^
  23|     sha256 = "08d04f6jc8kiwkx18ffig7wbjalqfryicxaw3am3kjsxsn2v19cb";

Can I simply ignore the error (ie. it’s just something to warn reviewers), or is there an other way to download the archive that doesn’t trigger an error?

1 Like

Just quote the url:

url = "";

Unquoted URL literals are deprecated.