Remove spatial containment and aggregation when nesting

The nest assign_object API now removes existing spatial containment and
aggregate relationships before creating the nest, matching the behavior
documented in its docstring and consistent with aggregate.assign_object.

Fix #7248

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/ifcopenshell-python/ifcopenshell/api/nest/assign_object.py

@@ -19,7 +19,9 @@
 from typing import Union
 
 import ifcopenshell
+import ifcopenshell.api.aggregate
 import ifcopenshell.api.owner
+import ifcopenshell.api.spatial
 import ifcopenshell.guid
 import ifcopenshell.util.element
 
@@ -137,7 +139,10 @@ def assign_object(
     if not objects_to_change:
         return is_nested_by
 
-    # NOTE: An object can both be nested and assigned to a container or an aggregate.
+    # Can be either only nested, aggregated, or contained at the same time.
+    possibly_contained = [o for o in objects_without_nests if hasattr(o, "ContainedInStructure")]
+    ifcopenshell.api.spatial.unassign_container(file, products=possibly_contained)
+    ifcopenshell.api.aggregate.unassign_object(file, products=objects_without_nests)
 
     # unassign elements from previous nests
     for nests in previous_nests_rels:

src/ifcopenshell-python/test/api/nest/test_assign_object.py

@@ -18,8 +18,10 @@
 
 import pytest
 
+import ifcopenshell.api.aggregate
 import ifcopenshell.api.nest
 import ifcopenshell.api.root
+import ifcopenshell.api.spatial
 import ifcopenshell.util.element
 import test.bootstrap
 
@@ -82,6 +84,24 @@ class TestAssignObject(test.bootstrap.IFC4):
         ifcopenshell.api.nest.assign_object(self.file, related_objects=subelements[2:3], relating_object=element2)
         assert rel.RelatedObjects == tuple(subelements[:2] + subelements[3:])
 
+    def test_nesting_removes_spatial_containment(self):
+        element = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWall")
+        subelement = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWall")
+        storey = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcBuildingStorey")
+        ifcopenshell.api.spatial.assign_container(self.file, products=[subelement], relating_structure=storey)
+        assert ifcopenshell.util.element.get_container(subelement) == storey
+        ifcopenshell.api.nest.assign_object(self.file, related_objects=[subelement], relating_object=element)
+        assert ifcopenshell.util.element.get_container(subelement) is None
+
+    def test_nesting_removes_aggregate(self):
+        element = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWall")
+        subelement = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcWall")
+        assembly = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcElementAssembly")
+        ifcopenshell.api.aggregate.assign_object(self.file, products=[subelement], relating_object=assembly)
+        assert ifcopenshell.util.element.get_aggregate(subelement) == assembly
+        ifcopenshell.api.nest.assign_object(self.file, related_objects=[subelement], relating_object=element)
+        assert ifcopenshell.util.element.get_aggregate(subelement) is None
+
 
 class TestAssignObjectIFC2X3(test.bootstrap.IFC2X3, TestAssignObject):
     pass