Container instances retained in memory after installing addon

[nestortmj]

I have been investigating a memory leak in one of our apps and I’ve noticed that as soon as I add @ember/jquery to a new ember project, I start to see tons of Container instances retained in memory after running tests.

Steps to reproduce:

1. ember new leak-test (ember-cli: 3.27.0, node: 14.17.0)
2. cd leak-test; ember install @ember/jquery
3. create an integration test that just renders a simple string
4. ember serve
5. open up http://localhost:4200/tests, let tests finish running and check the heap snapshot using Chrome’s DevTools

Here’s the test snippet I used for step 3:

// tests/integration/leak-test.js
import { module, test } from 'qunit';
import { setupRenderingTest } from 'ember-qunit';
import { render } from '@ember/test-helpers';
import hbs from 'htmlbars-inline-precompile';

module('Leak', function (hooks) {
  setupRenderingTest(hooks);
  for (let i = 0; i < 10; i++) {
    test(`test ${i}`, async function (assert) {
      await render(hbs`Hi`);
      assert.ok(true);
    });
  }
});

With @ember/jquery installed, I’m seeing one retained Container instance per test that has been executed (i.e. 10 instances using the snippet above). If I simply remove @ember/jquery, only one Container instance is retained.