Prevents creation of duplicate links

src/editor/js/structures/graph/graph.ts

@@ -295,6 +295,21 @@ export class Graph extends ManagedData {
         return true;
     }
 
+    getLink(sourceId: number, targetId: number, directionSensitive = true): Link {
+        return this.links.find((l) => {
+            if (l.sourceId === sourceId && l.targetId === targetId) {
+                return true;
+            }
+
+            // Check other direction if allowed
+            if (!directionSensitive && (l.sourceId === targetId && l.targetId === sourceId)) {
+                return true;
+            }
+
+            return false;
+        });
+    }
+
     getNode(id: number): Node {
         return this.getElementWithId(this.nodes, id);
     }
@@ -318,7 +333,7 @@ export class Graph extends ManagedData {
      * @returns True, if successful.
      */
     public addLink(link: Link): boolean {
-        if (this.data.links.includes(link)) {
+        if (this.getLink(link.sourceId, link.targetId, false) !== undefined) {
             return true; // Already exists in graph.
         }