re-adds edges if they are now connected and add does not add invalid edges (#3516)

lib/network/modules/EdgesHandler.js

@@ -422,12 +422,23 @@ class EdgesHandler {
   }
 
   /**
-   * Scan for missing nodes and remove corresponding edges, if any.
-   *
    * There is no direct relation between the nodes and the edges DataSet,
    * so the right place to do call this is in the handler for event `_dataUpdated`.
    */
   _updateState() {
+
+    this._addMissingEdges();
+
+    this._removeInvalidEdges();
+    
+  }
+
+  /**
+   * Scan for missing nodes and remove corresponding edges, if any.
+   * @private
+   */
+  _removeInvalidEdges() {
+    
     let edgesToDelete = [];
 
     util.forEach(this.body.edges, (edge, id) => {
@@ -447,6 +458,27 @@ class EdgesHandler {
 
     this.remove(edgesToDelete, false);
   }
+
+  /**
+   * add all edges from dataset that are not in the cached state
+   * @private
+   */ 
+  _addMissingEdges() {
+    
+     let edges = this.body.edges;
+     let edgesData = this.body.data.edges;
+     let addIds = [];
+
+     edgesData.forEach((edgeData, edgeId) => {
+         let edge = edges[edgeId];
+         if(edge===undefined)
+         {
+           addIds.push(edgeId);
+         }
+     });
+ 
+     this.add(addIds,true);
+   }  
 }
 
 export default EdgesHandler;