Function mountActivityChildren

packages/react-reconciler/src/ReactFiberBeginWork.js:891–928

(
  workInProgress: Fiber,
  nextProps: ActivityProps,
  renderLanes: Lanes,
)

}

function mountActivityChildren(
  workInProgress: Fiber,
  nextProps: ActivityProps,
  renderLanes: Lanes,
) {
  if (__DEV__) {
    const hiddenProp = (nextProps: any).hidden;
    if (hiddenProp !== undefined) {
      console.error(
        '<Activity> doesn\'t accept a hidden prop. Use mode="hidden" instead.\n' +
          '- <Activity %s>\n' +
          '+ <Activity %s>',
        hiddenProp === true
          ? 'hidden'
          : hiddenProp === false
            ? 'hidden={false}'
            : 'hidden={...}',
        hiddenProp ? 'mode="hidden"' : 'mode="visible"',
      );
    }
  }
  const nextChildren = nextProps.children;
  const nextMode = nextProps.mode;
  const mode = workInProgress.mode;
  const offscreenChildProps: OffscreenProps = {
    mode: nextMode,
    children: nextChildren,
  };
  const primaryChildFragment = mountWorkInProgressOffscreenFiber(
    offscreenChildProps,
    mode,
    renderLanes,
  );
  primaryChildFragment.ref = workInProgress.ref;
  workInProgress.child = primaryChildFragment;
  primaryChildFragment.return = workInProgress;
  return primaryChildFragment;
}

function retryActivityComponentWithoutHydrating(
  current: Fiber,