Currently, it is not possible to write a stream to file using writeFile() from the Promises API. However, this is supported by the Node.js Promises API.

Since the callback API does not support writing streams to file, only the promises API needs to be adjusted. I suggest collecting the stream data into a buffer at FsPromises.ts in writeFile(). This would only change the promises API and make it compliant to the Node.js Promises API.