Multi-polygon buildings missing during OSM import

[bjornblissing]

Blender and OS versions

Blender 2.92.0 running on Windows 10.

Describe the bug

Importing an OSM file which contains multi-polygon buildings will result in missing buildings.

How to Reproduce

Export an OSM file from the following map section: https://www.openstreetmap.org/#map=19/59.34306/18.04109

Import the OSM file into Blender. The result will be five buildings that miss geometry

This is a result of the buildings being defined with multiple polygons (i.e. Inner and Outer geometry).

Example:

<relation id="280199" visible="true" version="6" changeset="79504534" timestamp="2020-01-13T08:19:07Z" user="joihoin" uid="10431041">
  <member type="way" ref="41962200" role="inner"/>
  <member type="way" ref="41962199" role="outer"/>
  <member type="way" ref="41962202" role="inner"/>
  <member type="way" ref="41962201" role="inner"/>
  <tag k="building" v="apartments"/>
  <tag k="building:levels" v="7"/>
  <tag k="roof:levels" v="1"/>
  <tag k="type" v="multipolygon"/>
</relation>

My quick and dirty solution have been to write a simple script that processes the .osm file. This process simply locates the outer way node and append the building tags to that way node. This allows me to import these buildings.

So for the above example my script locate the way node 41962199 and append the building, building:levels, and roof:levels tags to that way-node:

<way id="41962199" visible="true" version="7" changeset="79505373" timestamp="2020-01-13T08:37:22Z" user="joihoin" uid="10431041">
  <nd ref="520000411"/>
  <nd ref="520000418"/>
  <nd ref="7127875152"/>
  <nd ref="7127875158"/>
  <nd ref="7127875154"/>
  <nd ref="520000416"/>
  <nd ref="2838385937"/>
  <nd ref="2838385935"/>
  <nd ref="520000414"/>
  <nd ref="520000411"/>
  <tag k="building" v="yes"/> <!-- Line added by processing script -->
  <tag k="building:levels" v="7"/> <!-- Line added by processing script -->
  <tag k="roof:levels" v="1"/> <!-- Line added by processing script -->
</way>

However, this will only generate the outer geometry of the building, and any interior cut out shapes will be omitted.