anchor.diff:    buildInputs = [ openssl proj geos xlibsWrapper sqlite gsl qwt exiv2
       fcgi libspatialindex libspatialite postgresql txt2tags libzip hdf5 netcdf
       qtbase qtwebkit qtsensors qca-qt5 qtkeychain qscintilla qtserialport qtxmlpatterns] ++
  -    (stdenv.lib.optional withGrass grass) ++ pythonBuildInputs;
  +    (lib.optional withGrass grass) ++ pythonBuildInputs;
   
     nativeBuildInputs = [ cmake flex bison ninja ];
   
  
positive.code: { stdenv, lib, fetchFromGitHub, cmake, ninja, flex, bison, proj, geos, xlibsWrapper, sqlite, gsl
  , qwt, fcgi, python3Packages, libspatialindex, libspatialite, postgresql
  , txt2tags, openssl, libzip, hdf5, netcdf, exiv2
  , qtbase, qtwebkit, qtsensors, qca-qt5, qtkeychain, qscintilla, qtserialport, qtxmlpatterns
  
negative.code:   cmakeFlags = [ "-DCMAKE_SKIP_BUILD_RPATH=OFF"
                   "-DPYQT5_SIP_DIR=${python3Packages.pyqt5}/share/sip/PyQt5"
                   "-DQSCI_SIP_DIR=${python3Packages.qscintilla-qt5}/share/sip/PyQt5" ] ++
                   lib.optional withGrass "-DGRASS_PREFIX7=${grass}/${grass.name}";
  
    meta = {
      description = "A Free and Open Source Geographic Information System";
      homepage = http://www.qgis.org;
      license = lib.licenses.gpl2Plus;
      platforms = with lib.platforms; linux;
      maintainers = with lib.maintainers; [ lsix ];
    };
  }
  