Real `DataTransferItem.getAsString()` breaks Clipboard methods

[ph-fritsche]

Reproduction example

https://codesandbox.io/p/sandbox/datatransferitem-getasstring-t693n7

Prerequisites

1. Create DataTransferItem
2. Read data of item per DataTransferItem.getAsString()

Expected behavior

Callback is called on new event loop step.

Actual behavior

The stub calls the callback immediately.

User-event version

14.5.2

Environment

Testing Library framework:

JS framework:

Test environment:

DOM implementation:

Additional context

The Clipboard methods rely on the immediate call of the callback and therefore break when the browser implementation of DataTransferItem is used.