Make sure all inverse refereneces are removed on node deletion

Iterating over the references list and deleting inside the same list
resulted in dangling inverse references if nodes where deleted.

Fix this by iterating over a copy of the references list.

asyncua/server/address_space.py

@@ -336,7 +336,7 @@ class NodeManagementService:
 
         if item.DeleteTargetReferences:
             for elem in self._aspace.keys():
-                for rdesc in self._aspace[elem].references:
+                for rdesc in self._aspace[elem].references[:]:
                     if rdesc.NodeId == item.NodeId:
                         self._aspace[elem].references.remove(rdesc)
 

tests/test_common.py

@@ -131,6 +131,26 @@ async def test_delete_nodes(opc):
     assert var not in childs
 
 
+async def test_delete_nodes_with_inverse_references(opc):
+    obj = opc.opc.nodes.objects
+    fold = await obj.add_folder(2, "FolderToDelete")
+    var = await fold.add_variable(2, "VarToDelete", 9.1)
+    var2 = await fold.add_variable(2, "VarWithReference", 9.2)
+    childs = await fold.get_children()
+    assert var in childs
+    assert var2 in childs
+    # add two references to var, this includes adding the inverse references to var2
+    await var.add_reference(var2.nodeid, reftype=ua.ObjectIds.HasDescription, forward=True, bidirectional=True)
+    await var.add_reference(var2.nodeid, reftype=ua.ObjectIds.HasEffect, forward=True, bidirectional=True)
+    await opc.opc.delete_nodes([var])
+    childs = await fold.get_children()
+    assert var not in childs
+    has_desc_refs = await var2.get_referenced_nodes(refs=ua.ObjectIds.HasDescription, direction=ua.BrowseDirection.Inverse)
+    assert len(has_desc_refs) == 0
+    has_effect_refs = await var2.get_referenced_nodes(refs=ua.ObjectIds.HasEffect, direction=ua.BrowseDirection.Inverse)
+    assert len(has_effect_refs) == 0
+
+
 async def test_delete_nodes_recursive(opc):
     obj = opc.opc.nodes.objects
     fold = await obj.add_folder(2, "FolderToDeleteR")