From ca77d0ef4c5f868fd3a5ba17ba0360c78c079a5e Mon Sep 17 00:00:00 2001
From: moklick <info@moritzklack.com>
Date: Wed, 22 Dec 2021 11:17:29 +0100
Subject: [PATCH] fix(edges): draw connection line when there are no edges
 closes #1785

---
 src/hooks/useVisibleEdges.ts | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/hooks/useVisibleEdges.ts b/src/hooks/useVisibleEdges.ts
index 204dfe40..148683ba 100644
--- a/src/hooks/useVisibleEdges.ts
+++ b/src/hooks/useVisibleEdges.ts
@@ -5,6 +5,8 @@ import { isEdgeVisible } from '../container/EdgeRenderer/utils';
 import { ReactFlowState, NodeInternals, Edge } from '../types';
 import { isNumeric } from '../utils';
 
+const defaultEdgeTree = [{ level: 0, isMaxLevel: true, edges: [] }];
+
 function groupEdgesByZLevel(edges: Edge[], nodeInternals: NodeInternals) {
   let maxLevel = -1;
 
@@ -23,7 +25,7 @@ function groupEdgesByZLevel(edges: Edge[], nodeInternals: NodeInternals) {
     return tree;
   }, {});
 
-  return Object.entries(levelLookup).map(([key, edges]) => {
+  const edgeTree = Object.entries(levelLookup).map(([key, edges]) => {
     const level = +key;
 
     return {
@@ -32,6 +34,12 @@ function groupEdgesByZLevel(edges: Edge[], nodeInternals: NodeInternals) {
       isMaxLevel: level === maxLevel,
     };
   });
+
+  if (edgeTree.length === 0) {
+    return defaultEdgeTree;
+  }
+
+  return edgeTree;
 }
 
 function useVisibleEdges(onlyRenderVisible: boolean, nodeInternals: NodeInternals) {