Function updatePortalComponent

packages/react-reconciler/src/ReactFiberBeginWork.js:3580–3603

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

}

function updatePortalComponent(
  current: Fiber | null,
  workInProgress: Fiber,
  renderLanes: Lanes,
) {
  pushHostContainer(workInProgress, workInProgress.stateNode.containerInfo);
  const nextChildren = workInProgress.pendingProps;
  if (current === null) {
    // Portals are special because we don't append the children during mount
    // but at commit. Therefore we need to track insertions which the normal
    // flow doesn't do during mount. This doesn't happen at the root because
    // the root always starts with a "current" with a null child.
    // TODO: Consider unifying this with how the root works.
    workInProgress.child = reconcileChildFibers(
      workInProgress,
      null,
      nextChildren,
      renderLanes,
    );
  } else {
    reconcileChildren(current, workInProgress, nextChildren, renderLanes);
  }
  return workInProgress.child;
}

let hasWarnedAboutUsingNoValuePropOnContextProvider = false;