Function warnAboutTransitionSubscriptions

packages/react/src/ReactStartTransition.js:185–202

(
  prevTransition: Transition | null,
  currentTransition: Transition,
)

}

function warnAboutTransitionSubscriptions(
  prevTransition: Transition | null,
  currentTransition: Transition,
) {
  if (__DEV__) {
    if (prevTransition === null && currentTransition._updatedFibers) {
      const updatedFibersCount = currentTransition._updatedFibers.size;
      currentTransition._updatedFibers.clear();
      if (updatedFibersCount > 10) {
        console.warn(
          'Detected a large number of updates inside startTransition. ' +
            'If this is due to a subscription please re-write it to use React provided hooks. ' +
            'Otherwise concurrent mode guarantees are off the table.',
        );
      }
    }
  }
}