Check if nodes exist on add_edge methods

releasenotes/notes/handle-non-existent-edge-15d70cfe60c89ac2.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    :meth:`rustworkx.PyGraph.add_edge` and :meth:`rustworkx.PyDiGraph.add_edge` and now raises an 
+    `IndexError` when one of the nodes does not exist in the graph. Previously, it caused the Python 
+    interpreter to exit with a `PanicException`

src/connectivity/mod.rs

@@ -398,7 +398,7 @@ pub fn graph_complement(py: Python, graph: &graph::PyGraph) -> PyResult<graph::P
                     || !complement_graph.has_edge(node_a.index(), node_b.index()))
             {
                 // avoid creating parallel edges in multigraph
-                complement_graph.add_edge(node_a.index(), node_b.index(), py.None());
+                complement_graph.graph.add_edge(node_a, node_b, py.None());
             }
         }
     }

src/digraph.rs

@@ -984,6 +984,11 @@ impl PyDiGraph {
     pub fn add_edge(&mut self, parent: usize, child: usize, edge: PyObject) -> PyResult<usize> {
         let p_index = NodeIndex::new(parent);
         let c_index = NodeIndex::new(child);
+        if !self.graph.contains_node(p_index) || !self.graph.contains_node(c_index) {
+            return Err(PyIndexError::new_err(
+                "One of the endpoints of the edge does not exist in graph",
+            ));
+        }
         let out_index = self._add_edge(p_index, c_index, edge)?;
         Ok(out_index)
     }

src/graph.rs

@@ -748,10 +748,15 @@ impl PyGraph {
     ///     of an existing edge with ``multigraph=False``) edge.
     /// :rtype: int
     #[pyo3(text_signature = "(self, node_a, node_b, edge, /)")]
-    pub fn add_edge(&mut self, node_a: usize, node_b: usize, edge: PyObject) -> usize {
+    pub fn add_edge(&mut self, node_a: usize, node_b: usize, edge: PyObject) -> PyResult<usize> {
         let p_index = NodeIndex::new(node_a);
         let c_index = NodeIndex::new(node_b);
-        self._add_edge(p_index, c_index, edge)
+        if !self.graph.contains_node(p_index) || !self.graph.contains_node(c_index) {
+            return Err(PyIndexError::new_err(
+                "One of the endpoints of the edge does not exist in graph",
+            ));
+        }
+        Ok(self._add_edge(p_index, c_index, edge))
     }
 
     /// Add new edges to the graph.
@@ -1604,7 +1609,7 @@ impl PyGraph {
         }
 
         for (source, weight) in edges {
-            self.add_edge(source.index(), node_index.index(), weight);
+            self.add_edge(source.index(), node_index.index(), weight)?;
         }
 
         Ok(node_index.index())

src/tree.rs

@@ -130,7 +130,7 @@ pub fn minimum_spanning_tree(
         .edges
         .iter()
     {
-        spanning_tree.add_edge(edge.0, edge.1, edge.2.clone_ref(py));
+        spanning_tree.add_edge(edge.0, edge.1, edge.2.clone_ref(py))?;
     }
 
     Ok(spanning_tree)

tests/rustworkx_tests/digraph/test_edges.py

@@ -962,3 +962,8 @@ def test_extend_from_weighted_edge_list(self):
         graph.extend_from_weighted_edge_list(edge_list)
         self.assertEqual(len(graph), 4)
         self.assertEqual(["a", "b", "c", "d", "e"], graph.edges())
+
+    def test_add_edge_non_existent(self):
+        g = rustworkx.PyDiGraph()
+        with self.assertRaises(IndexError):
+            g.add_edge(2, 3, None)

tests/rustworkx_tests/graph/test_edges.py

@@ -817,3 +817,8 @@ def test_extend_from_weighted_edge_list(self):
         graph.extend_from_weighted_edge_list(edge_list)
         self.assertEqual(len(graph), 4)
         self.assertEqual(["a", "b", "c", "d", "e"], graph.edges())
+
+    def test_add_edge_non_existent(self):
+        g = rustworkx.PyGraph()
+        with self.assertRaises(IndexError):
+            g.add_edge(2, 3, None)