unoplatform/uno · error · Error

No pending drag and drop data.

Error message

No pending drag and drop data.

What it means

Thrown by DragDropExtension.retrieveText when _pendingDropData on the current DragDropExtension instance is null. _pendingDropData (the DataTransfer object) is set during dragenter and cleared to null on dragleave or drop completion. This means retrieveText was called outside the active drag-drop window.

Source

Thrown at src/Uno.UI/ts/Windows/ApplicationModel/DataTransfer/DragAndDropExtension.ts:156

				evt.dataTransfer.dropEffect = ((args.acceptedOperation) as any);
			} finally {
				// No matter if the managed code handled the event, we want to prevent thee default behavior (like opening a drop link)
				evt.preventDefault();

				if (evt.type == "dragleave" || evt.type == "drop") {
					this._pendingDropData = null;
					this._pendingDropId = 0;
				}
			}
		}

		public static async retrieveText(itemId: number): Promise<string> {

			const current = DragDropExtension._current;
			const data = current?._pendingDropData;
			if (data == null) {
				throw new Error("No pending drag and drop data.");
			}

			return new Promise((resolve, reject) => {
				const item = data.items[itemId];
				const timeout = setTimeout(() => reject("Timeout: for security reason, you cannot access data before drop."), 15000);

				item.getAsString(str => {
					clearTimeout(timeout);
					resolve(str);
				});
			});
		}

		public static async retrieveFiles(itemIds: number[]): Promise<string> {

			const data = DragDropExtension._current?._pendingDropData;
			if (data == null) {
				throw new Error("No pending drag and drop data.");

View on GitHub (pinned to 0418340488)

Solutions

1. Only call retrieveText while the drag-drop operation is still pending (between dragenter and drop/dragleave).
2. In the managed drop handler, retrieve text content synchronously within the drop event callback before the TS side clears _pendingDropData.
3. Guard the managed call with a check that the drag-drop extension is active and has pending data.

Example fix

// before: retrieveText called after drop completed
// (DataTransfer already nulled in finally block)
DragDropExtension.retrieveText(itemId); // throws

// after: retrieve inside the drop event before clearing
// Managed OnDrop handler should call retrieveText
// before the event finishes processing.

// Before retrieveText, check pending data is still available
const current = (<any>DragDropExtension)._current;
if (current?._pendingDropData == null) {
    // no active drag — do not retrieve
    return null;
}

try {
    const text = await DragDropExtension.retrieveText(itemId);
} catch (e) {
    if (e.message === 'No pending drag and drop data.') {
        // drop already completed — nothing to retrieve
    } else { throw e; }
}

When it happens

Trigger: C# calls retrieveText(itemId) when there is no active drag (no _current instance or _current._pendingDropData is null), or after the drop has already completed (the finally block at line 144-147 clears _pendingDropData on dragleave/drop).

Common situations: Calling retrieveText after the drop event has been processed and the DataTransfer was nulled; calling it before any dragenter has set the data; a timing gap where the managed retrieve call arrives after the DOM cleared the pending data.

Related errors

• A DragDropExtension has already been enabled
• The current DragDropExtension does not match the provided ar
• retrieveFiles failed to find pending drag and drop data for
• Item ${guid} is a directory handle. You cannot use it as a F
• The staged content was released when the download was trigge

AI-assisted analysis of unoplatform/uno@0418340488 (2026-08-13). Data as JSON: /api/errors/508c208a8c14528e. Report an issue: GitHub.