New utility to get spatial and object decompositions from any IFC element

src/ifcopenshell-python/ifcopenshell/util/element.py

@@ -86,6 +86,20 @@ def get_container(element):
         return element.ContainedInStructure[0].RelatingStructure
 
 
+def get_decomposition(element):
+    queue = [element]
+    results = []
+    while queue:
+        element = queue.pop()
+        for rel in getattr(element, "ContainsElements", []):
+            queue.extend(rel.RelatedElements)
+            results.extend(rel.RelatedElements)
+        for rel in getattr(element, "IsDecomposedBy", []):
+            queue.extend(rel.RelatedObjects)
+            results.extend(rel.RelatedObjects)
+    return results
+
+
 def get_aggregate(element):
     if hasattr(element, "Decomposes") and element.Decomposes:
         return element.Decomposes[0].RelatingObject

src/ifcopenshell-python/test/util/test_element.py

@@ -174,6 +174,18 @@ class TestGetContainerIFC4(test.bootstrap.IFC4):
         assert ifcopenshell.util.element.get_container(subelement) == building
 
 
+class TestGetDecompositionIFC4(test.bootstrap.IFC4):
+    def test_getting_decomposed_subelements_of_an_element(self):
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcElementAssembly")
+        subelement = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcBeam")
+        building = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcBuilding")
+        ifcopenshell.api.run("spatial.assign_container", self.file, product=element, relating_structure=building)
+        ifcopenshell.api.run("aggregate.assign_object", self.file, product=subelement, relating_object=element)
+        results = ifcopenshell.util.element.get_decomposition(building)
+        assert element in results
+        assert subelement in results
+
+
 class TestGetAggregateIFC4(test.bootstrap.IFC4):
     def test_getting_the_containing_aggregate_of_a_subelement(self):
         element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")