anchor.diff:    };
   
     nativeBuildInputs = [
  -    docbook_xsl
  +    docbook-xsl-nons
       gtk-doc
       meson
       ninja
  
positive.code:   version = "unstable-2021-05-01";
  
    outputs = [ "out" "dev" "devdoc" ];
    outputBin = [ "dev" ];
  
    src = fetchFromGitLab {
      domain = "gitlab.gnome.org";
  
negative.code: { lib
  , stdenv
  , fetchFromGitLab
  , docbook-xsl-nons
  , gtk-doc
  , meson
  , ninja
  