Fix panic in dagre_rust remove_edge_label_proxies on edge labels

src/lib.rs

@@ -339,4 +339,55 @@ mod tests {
         assert!(svg.contains("Dogs"));
         assert!(!svg.contains("Syntax error in text"));
     }
+
+    // Regression tests for dagre_rust edge label proxy crash (unwrap on None)
+    // See: vendor/dagre_rust/src/layout/mod.rs remove_edge_label_proxies()
+
+    #[test]
+    fn test_flowchart_edge_labels() {
+        let svg = render(
+            r#"flowchart LR
+  A([Start]) --> B{Decision}
+  B -->|yes| C[/Do thing/]
+  B -->|no| D[\Skip\]
+  C --> E[[End]]
+  D --> E"#,
+        )
+        .unwrap();
+        assert!(svg.contains("<svg"));
+        assert!(svg.contains("</svg>"));
+    }
+
+    #[test]
+    fn test_state_diagram_with_labels() {
+        let svg = render(
+            r#"stateDiagram-v2
+[*] --> Idle
+Idle --> Active : start
+state "Waiting" as Wait
+Wait --> Active"#,
+        )
+        .unwrap();
+        assert!(svg.contains("<svg"));
+        assert!(svg.contains("</svg>"));
+    }
+
+    #[test]
+    fn test_er_diagram() {
+        let svg = render(
+            r#"erDiagram
+CUSTOMER ||--o{ ORDER : places
+CUSTOMER {
+string id
+string name
+}
+ORDER {
+string id
+date created_at
+}"#,
+        )
+        .unwrap();
+        assert!(svg.contains("<svg"));
+        assert!(svg.contains("</svg>"));
+    }
 }

vendor/dagre_rust/src/layout/mod.rs

@@ -388,9 +388,11 @@ pub fn remove_edge_label_proxies(g: &mut Graph<GraphConfig, GraphNode, GraphEdge
     let node = g.node(v).unwrap();
     if node.dummy.is_some() && node.dummy.clone().unwrap() == "edge-proxy" {
       let rank = node.rank.unwrap_or(0);
-      let graph_edge_ = g.edge_mut_with_obj(&node.e.clone().unwrap());
-      if let Some(graph_edge) = graph_edge_ {
-        graph_edge.label_rank = Some(rank);
+      if let Some(edge_ref) = node.e.clone() {
+        let graph_edge_ = g.edge_mut_with_obj(&edge_ref);
+        if let Some(graph_edge) = graph_edge_ {
+          graph_edge.label_rank = Some(rank);
+        }
       }
       g.remove_node(v);
     }