Merge pull request #218 from OpenFreeEnergy/issue_217_ligand_network_…

…no_edges

Issue 217 ligand network no edges

gufe/ligandnetwork.py

@@ -2,6 +2,7 @@
 # For details, see https://github.com/OpenFreeEnergy/gufe
 from __future__ import annotations
 
+from itertools import chain
 import json
 import networkx as nx
 from typing import FrozenSet, Iterable, Optional
@@ -30,7 +31,8 @@ def __init__(
             nodes = []
 
         self._edges = frozenset(edges)
-        edge_nodes = set.union(*[{edge.componentA, edge.componentB} for edge in edges])
+        edge_nodes = set(chain.from_iterable((e.componentA, e.componentB)
+                                             for e in edges))
         self._nodes = frozenset(edge_nodes) | frozenset(nodes)
         self._graph = None
 

gufe/tests/test_ligand_network.py

@@ -266,3 +266,11 @@ def test_is_connected(self, simple_network):
 
     def test_is_not_connected(self, singleton_node_network):
         assert not singleton_node_network.network.is_connected()
+
+
+def test_empty_ligand_network(mols):
+    # issue #217
+    n = LigandNetwork(edges=[], nodes=[mols[0]])
+
+    assert len(n.edges) == 0
+    assert len(n.nodes) == 1