React 18: "missing act()" warnings partially missing if a prior render threw

[eps1lon]

Specifically An update to * inside a test was not wrapped in act(...) is not logged when a prior update threw.

failing test (#21766)

// @gate __DEV__
it('warns if a setState is called outside of act(...) after a component threw', () => {
  let setValue = null;
  function App({defaultValue}) {
    if (defaultValue === undefined) {
      throw new Error();
    }
    const [value, _setValue] = React.useState(defaultValue);
    setValue = _setValue;
    return value;
  }

  expect(() => {
    act(() => {
      render(<App defaultValue={undefined} />, container);
    });
  }).toThrow();

  act(() => {
    rerender(<App defaultValue={0} />, container);
  });

  expect(() => setValue(1)).toErrorDev([
    'An update to App inside a test was not wrapped in act(...).',
  ]);
});

What I noticed is that in

react/packages/react-reconciler/src/ReactFiberWorkLoop.new.js

Lines 2855 to 2865 in 27c9c95

	if (
	warnsIfNotActing === true &&
	executionContext === NoContext &&
	ReactCurrentActQueue.current === null &&
	// Our internal tests use a custom implementation of `act` that works by
	// mocking the Scheduler package. Disable the `act` warning.
	// TODO: Maybe the warning should be disabled by default, and then turned
	// on at the testing frameworks layer? Instead of what we do now, which
	// is check if a `jest` global is defined.
	ReactCurrentActQueue.disableActWarning === false
	) {

the executionContext will still equal RetryAfterError when we would expect a "missing act" warning.

"missing act" warnings are working as expected with legacy roots.