Function pushTransition

packages/react-reconciler/src/ReactFiberTransition.js:275–299

(
  offscreenWorkInProgress: Fiber,
  prevCachePool: SpawnedCachePool | null,
  newTransitions: Array<Transition> | null,
)

}

export function pushTransition(
  offscreenWorkInProgress: Fiber,
  prevCachePool: SpawnedCachePool | null,
  newTransitions: Array<Transition> | null,
): void {
  if (prevCachePool === null) {
    push(resumedCache, resumedCache.current, offscreenWorkInProgress);
  } else {
    push(resumedCache, prevCachePool.pool, offscreenWorkInProgress);
  }

  if (enableTransitionTracing) {
    if (transitionStack.current === null) {
      push(transitionStack, newTransitions, offscreenWorkInProgress);
    } else if (newTransitions === null) {
      push(transitionStack, transitionStack.current, offscreenWorkInProgress);
    } else {
      push(
        transitionStack,
        transitionStack.current.concat(newTransitions),
        offscreenWorkInProgress,
      );
    }
  }
}

export function popTransition(workInProgress: Fiber, current: Fiber | null) {
  if (current !== null) {