Response promise resolves before response closes

[medikoo]

In some scenarios promise returned by e.g.response.text() resolves before 'close' event is emitted on Node.js response object (as emitted with requests's 'response' event).

It's not an issue per se, but:

• Not sure if that's on par with how Fetch works in a browser.
• It seems not possible to observe an async request/response process as a whole (it finalizes with 'close' event emitted on response, which is not exposed and ignored by node-fetch internals). It's an issue when e.g. we want to detect orphaned async flows, and for that want to guarantee that promises returned by fetch do not resolve prior response closes.

For example following test case will report an async leak in Node.js v12.2, when using node-fetch at v2.6.0

const fetch = require('node-fetch');

const checkAsyncLeak = () =>
  setTimeout(() => {
    throw new Error('Async leak!');
  }).unref();

fetch('https://google.com', { compress: false })
  .then(response => response.text())
  .then(() => {
    // All request related async jobs should be finalized by now
    checkAsyncLeak();
  });

[xxczaki]

This issue should no longer occur in the v3.x release.