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Portal stays visible indefinitely if unmounted immediately after mounting

See original GitHub issue

Current behaviour

When trying to remove a portal immediately after mounting it, it stays visible indefinitely. See the failing test below.

Expected behaviour

The portal is unmounted and does not stay visible.

Code sample

Here’s a minimal failing test case (something equivalent happened to me in more complicated, real world code)

import React, { useEffect, useState } from 'react';
import { Portal, Text } from 'react-native-paper';
import { render, waitForElement } from 'react-native-testing-library';

const TestComponent = () => {
  const [isPortalVisible, setIsPortalVisible] = useState(true);
  useEffect(() => {
    // Unmount the portal immediately after mounting it
    setIsPortalVisible(false);
  }, []);

  return (
    <Portal.Host>
      {isPortalVisible && (
        <Portal>
          <Text>{"I'm here"}</Text>
        </Portal>
      )}
    </Portal.Host>
  );
};

test('portal is properly unmounted', async () => {
  const component = render(<TestComponent />);

  // This expectation is failing, the portal is never unmounted, despite the useEffect
  await waitForElement(() => {
    const portalContent = component.queryByText("I'm here");
    if (portalContent) throw new Error('Portal is still visible');
  });
});

What have you tried

The cause seems to be with the await here: https://github.com/callstack/react-native-paper/blob/975cfa3be4956b629aa8255e226ff9ca068448eb/src/components/Portal/PortalConsumer.tsx#L10-L17

The await in componentDidMount causes a race condition with the synchronous unmounting: https://github.com/callstack/react-native-paper/blob/975cfa3be4956b629aa8255e226ff9ca068448eb/src/components/Portal/PortalConsumer.tsx#L25-L29

The portal gets (not really) unmounted before being mounted → it stays registered with the portal manager.

One possible fix is to make componentWillUnmount async too:

-  componentWillUnmount() {
+  async componentWillUnmount() {
     this._checkManager();

+    await Promise.resolve();
     this.props.manager.unmount(this._key);
   }

I’m not sure why the await Promise.resolve() was introduced, so I can’t tell for sure if it’s possible to fix this in a cleaner way.