fix issues assigning material sets and material lists

src/blenderbim/blenderbim/core/material.py

@@ -118,7 +118,6 @@ def assign_material(
             continue
 
         ifc.run("material.assign_material", products=[element], type=material_type, material=material)
-        material_tool.ensure_material_assigned(elements=[element], material_type=material_type, material=material)
         assigned_material = material_tool.get_material(element)
         assert assigned_material  # Type checker.
 
@@ -128,6 +127,7 @@ def assign_material(
             material_tool.add_material_to_set(material_set=material, material=default_material)
         elif material_tool.is_a_material_set(assigned_material):
             material_tool.add_material_to_set(material_set=assigned_material, material=material)
+        material_tool.ensure_material_assigned(elements=[element], material_type=material_type, material=material)
 
 
 def unassign_material(ifc: tool.Ifc, material_tool: tool.Material, objects: list[bpy.types.Object]) -> None:

src/blenderbim/blenderbim/tool/material.py

@@ -321,7 +321,8 @@ class Material(blenderbim.core.tool.Material):
     ) -> None:
         """Ensure blender materials are updated after a material assignment.
 
-        Designed to be called after material.assign_material API call."""
+        Designed to be called after material.assign_material API call.
+        For material sets it should be called after some item is already added to the material set."""
 
         # NOTE: adding/editing/removing layers/profiles/constituents is not supported.
         # Adding support for profiles/layers it only will be possible when we'll be adding styles

src/blenderbim/blenderbim/tool/model.py

@@ -1308,7 +1308,8 @@ class Model(blenderbim.core.tool.Model):
 
             obj = next(iter(mesh_users))
             element = tool.Ifc.get_entity(obj)
-            own_material = ifcopenshell.util.element.get_material(element, should_inherit=False)
+            assert element  # Type checker.
+            own_material = next(iter(ifcopenshell.util.element.get_materials(element, should_inherit=False)), None)
             inherited_mstyle = tool.Geometry.get_inherited_material_style(element)
 
             if assigned_material:

src/ifcopenshell-python/ifcopenshell/api/material/assign_material.py

@@ -74,6 +74,9 @@ def assign_material(
     :param material: The IfcMaterial or material set you are assigning here.
         If type is Usage then no need to provide `material`, it will be deduced
         from the element type automatically.
+        If IfcMaterial is provided as material and type is not IfcMaterial,
+        provided material will be ignored except for IfcMaterialList
+        where it will be used as part of the list.
     :type material: ifcopenshell.entity_instance, optional
     :return: IfcRelAssociatesMaterial entity
         or a list of IfcRelAssociatesMaterial entities