fix: call clearData in useDrag onDragStart (#8683)

* useDrag: clearData is onDragStart before writeToDataTransfer

* optional chaining to avoid test failures without mock

Author: reidbarber

packages/@react-aria/dnd/src/useDrag.ts

@@ -116,6 +116,8 @@ export function useDrag(options: DragOptions): DragResult {
     }
 
     let items = options.getItems();
+    // Clear existing data (e.g. selected text on the page would be included in some browsers)
+    e.dataTransfer.clearData?.();
     writeToDataTransfer(e.dataTransfer, items);
 
     let allowed = DROP_OPERATION.all;

packages/@react-aria/dnd/test/mocks.js

@@ -125,6 +125,14 @@ export class DataTransfer {
   getData(type) {
     return this.items._items.find(item => item.kind === 'string' && item.type === type)?._data;
   }
+
+  clearData(type) {
+    if (type) {
+      this.items._items = this.items._items.filter(item => item.type !== type);
+    } else {
+      this.items._items = [];
+    }
+  }
 }
 
 export class DragEvent extends MouseEvent {