[BUG 3.13] Observer on CP receiving wrong value

[simonihmig]

Here is a reproduction, that is failing starting w/ 3.13.0-beta.1 (same on canary): https://codesandbox.io/embed/my-app-i4i02?initialpath=/tests

The failing test is this one:

  test("case 3", function(assert) {
    assert.expect(3);

    const Dummy = EmberObject.extend({
      foo: true,

      _foo: computed("foo", {
        get() {
          return this.get("foo");
        },
        set(key, value) {
          // eslint-disable-line no-unused-vars
          return value;
        }
      }),

      _fooTracker: observer("_foo", function() {
        let value = this.get("_foo");
        assert.notOk(value);
      })
    });

    const subject = Dummy.create();

    assert.ok(subject.get("_foo"));
    subject.set("_foo", false);
    assert.notOk(subject.get("_foo"));
  });

_foo in the observer function is (still) true (makes the assertion fail), while it should be false as the observer is triggered by setting it explicitly to false. Another super weird thing is that the third assertion (the last line in the test) now also fails, while it does not fail when _foo is not read from in the observer (see the "case2" test in the sandbox).

Also the observer does see the updated value of true, when not observing the CP _foo, but directly the simple property foo (see "case1").

[pzuraq]

I believe this may be fixed by some changes in #18223

[rwjblue]

We should ensure (by adding a test)...

[simonihmig]

Ok, I'll try to add a PR with that failing test...

[simonihmig]

Here's a failing test: #18248

[simonihmig]

Fixed by #18248!