Allow union with just one topology to union in that topology

Author: arneboockmeyer

test/union_test.py

@@ -449,7 +449,9 @@ def test_union_in_one_topology():
     node_6 = Node(geo_node=EuclideanGeoNode(30, 0))
     edge_1 = Edge(node_1, node_2)
     edge_2 = Edge(node_2, node_3)
-    edge_3 = Edge(node_2, node_5, intermediate_geo_nodes=[EuclideanGeoNode(13, 5), EuclideanGeoNode(17, 5)])
+    edge_3 = Edge(
+        node_2, node_5, intermediate_geo_nodes=[EuclideanGeoNode(13, 5), EuclideanGeoNode(17, 5)]
+    )
     edge_4 = Edge(node_5, node_4)
     edge_5 = Edge(node_5, node_6)
     topology_a.add_nodes([node_1, node_2, node_3, node_4, node_5, node_6])

yaramo/operations/union.py

@@ -9,32 +9,44 @@ class Union:
     def union(
         topology_a: Topology, node_matching: Dict[Node, Node], topology_b: Topology = None
     ) -> Topology:
-        if not (
-            Union._are_all_nodes_in_topology(topology_a, node_matching.keys())
-            and Union._are_all_nodes_in_topology(topology_b, node_matching.values())
-        ):
-            raise ValueError(
-                "The node matching contains nodes, that are not inside the corresponding topology. Abort."
-            )
+        if topology_b is None:
+            if not (
+                Union._are_all_nodes_in_topology(topology_a, node_matching.keys())
+                and Union._are_all_nodes_in_topology(topology_a, node_matching.values())
+            ):
+                raise ValueError(
+                    "The node matching contains nodes, that are not inside the given topology. Abort."
+                )
+        else:
+            if not (
+                Union._are_all_nodes_in_topology(topology_a, node_matching.keys())
+                and Union._are_all_nodes_in_topology(topology_b, node_matching.values())
+            ):
+                raise ValueError(
+                    "The node matching contains nodes, that are not inside the corresponding topology. Abort."
+                )
 
         if not Union._are_all_nodes_ends(node_matching):
             raise ValueError(
                 "Some of the nodes in the matching are points. All nodes have to be ends. Abort."
             )
 
-        topology_ab = Topology()
-        OperationsHelper.copy_topology_metadata(topology_a, topology_ab)
-
-        topology_ab.nodes.update(topology_a.nodes)
-        topology_ab.nodes.update(topology_b.nodes)
-        topology_ab.edges.update(topology_a.edges)
-        topology_ab.edges.update(topology_b.edges)
-        topology_ab.signals.update(topology_a.signals)
-        topology_ab.signals.update(topology_b.signals)
-        topology_ab.routes.update(topology_a.routes)
-        topology_ab.routes.update(topology_b.routes)
-        topology_ab.vacancy_sections.update(topology_a.vacancy_sections)
-        topology_ab.vacancy_sections.update(topology_b.vacancy_sections)
+        topology_ab = topology_a
+
+        if topology_b is not None:
+            topology_ab = Topology()
+            OperationsHelper.copy_topology_metadata(topology_a, topology_ab)
+
+            topology_ab.nodes.update(topology_a.nodes)
+            topology_ab.nodes.update(topology_b.nodes)
+            topology_ab.edges.update(topology_a.edges)
+            topology_ab.edges.update(topology_b.edges)
+            topology_ab.signals.update(topology_a.signals)
+            topology_ab.signals.update(topology_b.signals)
+            topology_ab.routes.update(topology_a.routes)
+            topology_ab.routes.update(topology_b.routes)
+            topology_ab.vacancy_sections.update(topology_a.vacancy_sections)
+            topology_ab.vacancy_sections.update(topology_b.vacancy_sections)
 
         for node_a, node_b in node_matching.items():
             union_edge_a: Edge = node_a.connected_edges[0]