Convert the generator function into a TransformStream.

import { readableStreamFromIterable } from "https://deno.land/std@0.191.0/streams/readable_stream_from_iterable.ts";
import { toTransformStream } from "https://deno.land/std@0.191.0/streams/to_transform_stream.ts";

const readable = readableStreamFromIterable([0, 1, 2])
  .pipeThrough(toTransformStream(async function* (src) {
    for await (const chunk of src) {
      yield chunk * 100;
    }
  }));

for await (const chunk of readable) {
  console.log(chunk);
}
// output: 0, 100, 200