Error on tessellation request in IFC2X3

IfcTriangulatedFaceSet/IfcPolygonalFaceSet were introduced in
Fix #7992: IFC4 and do not exist in IFC2X3. Previously, requesting an
IfcTessellatedFaceSet representation in an IFC2X3 file silently
fell back to a faceted brep after unassigning material sets.
Add a guard in the update_representation operator (user-facing
error) and in the add_representation API (ValueError) so the
unsupported request is caught instead of failing silently.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/bim/module/geometry/operator.py

@@ -546,6 +546,13 @@ class UpdateRepresentation(bpy.types.Operator, tool.Ifc.Operator):
         objs = [bpy.data.objects[obj_name]] if obj_name else context.selected_objects
         self.file = tool.Ifc.get()
 
+        # Tessellated face sets (IfcTriangulatedFaceSet/IfcPolygonalFaceSet) were
+        # introduced in IFC4 and do not exist in IFC2X3. Catch this early so we
+        # don't silently fall back to a faceted brep after stripping materials.
+        if self.ifc_representation_class == "IfcTessellatedFaceSet" and self.file.schema == "IFC2X3":
+            self.report({"ERROR"}, "Tessellated face sets are not supported in IFC2X3.")
+            return {"CANCELLED"}
+
         for obj in objs:
             # TODO: write unit tests to see how this bulk operation handles
             # contradictory ifc_representation_class values and when

src/ifcopenshell-python/ifcopenshell/api/geometry/add_representation.py

@@ -121,6 +121,12 @@ class Usecase:
     blender_object: bpy.types.Object
 
     def execute(self) -> Union[ifcopenshell.entity_instance, None]:
+        # IfcTriangulatedFaceSet/IfcPolygonalFaceSet were introduced in IFC4 and
+        # do not exist in IFC2X3. Without this guard create_mesh_representation()
+        # silently falls back to a faceted brep, ignoring the requested class.
+        if self.settings["ifc_representation_class"] == "IfcTessellatedFaceSet" and self.file.schema == "IFC2X3":
+            raise ValueError("Tessellated face sets (IfcTessellatedFaceSet) are not supported in IFC2X3.")
+
         self.is_manifold = None
         self.coordinate_offset = self.settings["coordinate_offset"]
         self.geometry = self.settings["geometry"]