Function updateHostSingleton

packages/react-reconciler/src/ReactFiberBeginWork.js:2046–2066

(
  current: Fiber | null,
  workInProgress: Fiber,
  renderLanes: Lanes,
)

}

function updateHostSingleton(
  current: Fiber | null,
  workInProgress: Fiber,
  renderLanes: Lanes,
) {
  pushHostContext(workInProgress);

  if (current === null) {
    claimHydratableSingleton(workInProgress);
  }

  const nextChildren = workInProgress.pendingProps.children;
  reconcileChildren(current, workInProgress, nextChildren, renderLanes);
  markRef(current, workInProgress);
  if (current === null) {
    // We mark Singletons with a static flag to more efficiently manage their
    // ownership of the singleton host instance when in offscreen trees including Suspense
    workInProgress.flags |= LayoutStatic;
  }
  return workInProgress.child;
}

function updateHostText(current: null | Fiber, workInProgress: Fiber) {
  if (current === null) {