Support passing ReadableStream to Deno.writeFile

[lucacasonato]

This would make streaming data to disk really easy. writeFile cancellations should be propagated into the readable stream reading. Only ReadableStream<Uint8Array> would be allowed. writeTextFile would allow ReadableStream<string>.

This would be in addition to allowing Uint8Array / string as we do now.

[duncanmak]

Maybe this can be closed? See #13614.

[irustm]

It would be nice, since right now the file upload goes something like this:

import { readAll, readerFromStreamReader } from "https://deno.land/std@0.171.0/streams/conversion.ts";

//// body: FormData
const firstFile = body.get('file');

if (firstFile instanceof File) {
      const fileDest = firstFile.name;

      // write the file if the file has content in memory
      if (firstFile.size) {
        const reader = firstFile.stream().getReader();
        const stream = readerFromStreamReader(reader);
        const file = await readAll(stream);

        await Deno.writeFile(fileDest, file, { append: true });
      }
}

[bartlomieju]

This is reasonable and we should implement this. PRs are very welcome!

[wwoast]

#19697 tracks a bug in the passing of ReadableStream to Deno.writeFile. I uncovered the same bug last night when I was looking for ways to get rid of my use of streams/copy, prior to discovering the newer io/copy.