useTransition - startTransition does not work on React.memo when is SimpleMemoComponent

[salvoravida]

Do you want to request a feature or report a bug?
bug
What is the current behavior?
useTransition - startTransition do not work on React.memo when is SimpleMemoComponent

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem. Your bug will get fixed much faster if we can run your code and it doesn't have dependencies other than React. Paste the link to your JSFiddle (https://jsfiddle.net/Luktwrdm/) or CodeSandbox (https://codesandbox.io/s/new) example below:

What is the expected behavior?
startTransition work with SimpleMemoComponent

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

[threepointone]

Please make a reproducing example on codesandbox, it’s not clear what you’re asking.

[salvoravida]

isPending not working

Click on "With Transition Start"
OK -> https://codesandbox.io/s/test-redux-in-concurrent-mode-with-react-redux-salvoravidareact-redux-9lun7
KO -> https://codesandbox.io/s/test-redux-in-concurrent-mode-with-react-redux-salvoravidareact-redux-68pbd

only line 85 is changed

const _MyComponent = () => {
  const status = useSelector(s => s.status);

  if (status === STATUS.PENDING) {
    throw promise;
  }
  return null;
};

//_MyComponent.defaultProps = {};
const MyComponent = React.memo(_MyComponent);

the problem maybe is here in react-dom

function updateMemoComponent(current$$1, workInProgress, Component, nextProps, updateExpirationTime, renderExpirationTime) {
  if (current$$1 === null) {
    var type = Component.type;

    if (isSimpleFunctionComponent(type) && Component.compare === null && // SimpleMemoComponent codepath doesn't resolve outer props either.
    Component.defaultProps === undefined) {
      var resolvedType = type;

      {
        resolvedType = resolveFunctionForHotReloading(type);
      } // If this is a plain function component without default props,
      // and with only the default shallow comparison, we upgrade it
      // to a SimpleMemoComponent to allow fast path updates.


      workInProgress.tag = SimpleMemoComponent;
      workInProgress.type = resolvedType;

      {
        validateFunctionComponentInDev(workInProgress, type);
      }

      return updateSimpleMemoComponent(current$$1, workInProgress, resolvedType, nextProps, updateExpirationTime, renderExpirationTime);
    }

[dai-shi]

@salvoravida Hi, do you think you can create a smaller reproduction? You don't need redux or even useTransition to reproduce this bug, do you? If what you are observing is correct, this issue is related with #17314.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution.

[stale]

Closing this issue after a prolonged period of inactivity. If this issue is still present in the latest release, please create a new issue with up-to-date information. Thank you!

[gaearon]

We haven't checked if this is a bug. It might be.

[dai-shi]

@gaearon Probably, this issue and #17314 can be merged into #17028. All of them originated from my code. #17028 has a small reproduction, while this issue is good because it points out the issue only happens with React.memo only when it has no areEqual.

[acdlite]

Thanks for the bug report!

I believe this was fixed by #18091

You can confirm using react@0.0.0-experimental-ea6ed3dbb and react-dom@0.0.0-experimental-ea6ed3dbb.

I'm going to close this issue, but if the bug persists please comment and we'll reopen.

[dai-shi]

Confirmed the fix with 0.0.0-experimental-5de5b6150 on my end. Thanks so much!

[salvoravida]

great! thanks!