supplementary variables in cubes after preprocessing functions

[rebeccaherman1]

I am using this notebook as a guide while I attempt to develop my recipe and diagnostic scripts. Upon loading the initial cube, I believe I see that the supplementary variable areacella included in the cube as cell_area under Cell measures, but the moment I restrict the domain with extract_region, Cell measures disappears, taking cell_area with it. Is areacella no longer part of the cube? If it is, where did it go?

[bouweandela]

Fixed by #2166, which should be available in the upcoming v2.10 release.