From abf00187bb89b1de6ea7a8b45e0920d7766d91a3 Mon Sep 17 00:00:00 2001
From: jasonpul <61257274+jasonpul@users.noreply.github.com>
Date: Sun, 11 Oct 2020 17:51:08 -0400
Subject: [PATCH] Update graph.ts

added check to verify handle exists in node
---
 src/utils/graph.ts | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/utils/graph.ts b/src/utils/graph.ts
index 700f982b..9c427786 100644
--- a/src/utils/graph.ts
+++ b/src/utils/graph.ts
@@ -65,10 +65,14 @@ export const addEdge = (edgeParams: Edge | Connection, elements: Elements): Elem
       throw new Error(`Can't create edge. Node with id=${id} does not exist.`);
     }
   });
-  // need to check if handles exist
-  // 
-  // 
-  // 
+  
+  // make sure that the handles exists in each node
+  const handleElements = Array.from(document.getElementsByClassName("react-flow__handle")) as HTMLDivElement[]
+  [[edgeParams.source, edgeParams.sourceHandle], [edgeParams.target, edgeParams.targetHandle]].forEach(([nodeId, handleId]) => {
+    if (!handleElements.find((he) => he.getAttribute('data-nodeid') === nodeId && he.getAttribute('data-handleid') === handleId)) {
+      throw new Error(`Can't create edge. Handle with id=${handleId} does not exist within Node with id=${nodeId}.`);
+    }
+  })
 
   let edge: Edge
   if (isEdge(edgeParams)) {