feat(svelte): add useHandleConnections, useNodesData and useUpdateNodeData

packages/system/src/xyhandle/XYHandle.ts

@@ -58,12 +58,10 @@ export type XYHandleInstance = {
 type Result = {
   handleDomNode: Element | null;
   isValid: boolean;
-  connection: Connection;
+  connection: Connection | null;
   endHandle: ConnectingHandle | null;
 };
 
-const nullConnection: Connection = { source: null, target: null, sourceHandle: null, targetHandle: null };
-
 const alwaysValid = () => true;
 
 let connectionStartHandle: ConnectingHandle | null = null;
@@ -197,7 +195,7 @@ function onPointerDown(
       return resetRecentHandle(prevActiveHandle, lib);
     }
 
-    if (connection.source !== connection.target && handleDomNode) {
+    if (connection?.source !== connection?.target && handleDomNode) {
       resetRecentHandle(prevActiveHandle, lib);
       prevActiveHandle = handleDomNode;
       handleDomNode.classList.add('connecting', `${lib}-flow__handle-connecting`);
@@ -269,7 +267,7 @@ function isValidHandle(
   const result: Result = {
     handleDomNode: handleToCheck,
     isValid: false,
-    connection: nullConnection,
+    connection: null,
     endHandle: null,
   };
 
@@ -280,6 +278,10 @@ function isValidHandle(
     const connectable = handleToCheck.classList.contains('connectable');
     const connectableEnd = handleToCheck.classList.contains('connectableend');
 
+    if (!handleNodeId) {
+      return result;
+    }
+
     const connection: Connection = {
       source: isTarget ? handleNodeId : fromNodeId,
       sourceHandle: isTarget ? handleId : fromHandleId,