currently all analysis thorns that perform integration of grid functions have to know about multipatch and inherit from Coordinates (or do magic with CCTK_VarDataPtr). This is different from eg the situation for AMR/no AMR where a thorn can be blissfully unaware of the situation present as long as it uses standard Cactus facilities.
Currently the workaround is to have a dummy Coordinates thorn (CartesianCoordinates) that provides volume_form of delta_space[] etc. An alternative option would be to have the driver (Carpet) offer a dedicated reduction that multiplies the to-be-reduced grid function by the volume form (and by the coarsest grid spacing if no multipatch code is present). That way the only change required by user thorns would be a change from "sum" to "integrate" and removal of a multiplication by delta_space at the end (which makes the code simpler).
noise to test "follow" functionality