cancelling fetch after promise has been resolved

[ronag]

Given my current understand of the spec the following unit test (from node-fetch) should always fail:

it('should reject response body methods immediately with AbortError when aborted before stream is disturbed', () => {
  return expect(fetch(
    `${base}slow`,
    { signal: controller.signal }
  ))
    .to.eventually.be.fulfilled
    .then(res => {
      controller.abort()
      return expect(res.text())
        .to.eventually.be.rejected
        .and.be.an.instanceof(Error)
        .and.have.property('name', 'AbortError')
    })
})

The response is cancelled before res.text() starts reading from the response body and given the current way ReadableStream.cancel works we will just read an empty string as success. There is no propagation of the abort error to the reader of the response stream.

Refs: nodejs/node#39715

[ronag]

Use controller.error.