React Fiber 水合上下文

一、作用

二、找到第一个挂起的（元素）

备注

• isSuspenseInstancePending() 由宿主环境提供
• isSuspenseInstanceFallback() 由宿主环境提供

export function findFirstSuspended(row: Fiber): null | Fiber {
  let node = row;
  while (node !== null) {
    if (node.tag === SuspenseComponent) {
      const state: SuspenseState | null = node.memoizedState;
      if (state !== null) {
        const dehydrated: null | SuspenseInstance = state.dehydrated;
        if (
          dehydrated === null ||
          isSuspenseInstancePending(dehydrated) ||
          isSuspenseInstanceFallback(dehydrated)
        ) {
          return node;
        }
      }
    } else if (
      node.tag === SuspenseListComponent &&
      // Independent revealOrder can't be trusted because it doesn't
      // keep track of whether it suspended or not.
      //
      // 独立的 revealOrder 不能被信任，因为它不会跟踪是否被挂起。
      node.memoizedProps.revealOrder !== 'independent'
    ) {
      const didSuspend = (node.flags & DidCapture) !== NoFlags;
      if (didSuspend) {
        return node;
      }
    } else if (node.child !== null) {
      node.child.return = node;
      node = node.child;
      continue;
    }
    if (node === row) {
      return null;
    }
    while (node.sibling === null) {
      if (node.return === null || node.return === row) {
        return null;
      }
      node = node.return;
    }
    node.sibling.return = node.return;
    node = node.sibling;
  }
  return null;
}