Function updateViewTransition

packages/react-reconciler/src/ReactFiberBeginWork.js:3530–3578

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

}

function updateViewTransition(
  current: Fiber | null,
  workInProgress: Fiber,
  renderLanes: Lanes,
) {
  const pendingProps: ViewTransitionProps = workInProgress.pendingProps;
  if (pendingProps.name != null && pendingProps.name !== 'auto') {
    // Explicitly named boundary. We track it so that we can pair it up with another explicit
    // boundary if we get deleted.
    workInProgress.flags |=
      current === null
        ? ViewTransitionNamedMount | ViewTransitionNamedStatic
        : ViewTransitionNamedStatic;
  } else {
    // The server may have used useId to auto-assign a generated name for this boundary.
    // We push a materialization to ensure child ids line up with the server.
    if (getIsHydrating()) {
      pushMaterializedTreeId(workInProgress);
    }
  }
  if (__DEV__) {
    // $FlowFixMe[prop-missing]
    if (pendingProps.className !== undefined) {
      const example =
        typeof pendingProps.className === 'string'
          ? JSON.stringify(pendingProps.className)
          : '{...}';
      if (!didWarnAboutClassNameOnViewTransition[example]) {
        didWarnAboutClassNameOnViewTransition[example] = true;
        console.error(
          '<ViewTransition> doesn\'t accept a "className" prop. It has been renamed to "default".\n' +
            '-   <ViewTransition className=%s>\n' +
            '+   <ViewTransition default=%s>',
          example,
          example,
        );
      }
    }
  }
  if (current !== null && current.memoizedProps.name !== pendingProps.name) {
    // If the name changes, we schedule a ref effect to create a new ref instance.
    workInProgress.flags |= Ref | RefStatic;
  } else {
    markRef(current, workInProgress);
  }
  const nextChildren = pendingProps.children;
  reconcileChildren(current, workInProgress, nextChildren, renderLanes);
  return workInProgress.child;
}

function updatePortalComponent(
  current: Fiber | null,