Landcover and amenity-points drawing order and tag prioritization not in sync

[imagico]

Since #3441 we set the drawing order in the landcover layer by feature in addition to way_area to have a defined order in case of features with identical geometries.

However for features with multiple landcover tags the prioritization is done with COALESCE() - and the order there is not alphabetical:

openstreetmap-carto/project.mml

Line 91 in 9bda286

COALESCE(aeroway, golf, amenity, wetland, power, landuse, leisure, man_made, "natural", shop, tourism, highway, railway) AS feature

That means a feature with two landcover tags will potentially render differently from the case with the same two landcover tags being applied to two identical geometries, potentially leading to confusion.

This is not a practically overly significant scenario - still it would be good to correct that and to document this better with a suitable comment in the code.

[imagico]

Same problem applies to amenity-points by the way - there the COALESCE() order is more complex and partly deliberately chosen. The amenity-points case is actually practically more relevant. See also #4676 and #3880.