React Native启动Metro打包器失败：resp.asserted-states不可迭代错误

问题场景 #

按照官方流程创建新React Native项目，在Windows 11系统（NodeJS 18.16.1）下执行npm start时，Metro打包器无法启动，抛出TypeError: resp.asserted-states is not iterable错误。相同NodeJS版本在WSL环境下可正常运行。

报错信息 #

PS D:\Sources\Personal\AwesomeProject> npm start

> AwesomeProject@0.0.1 start
> react-native start

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                Welcome to Metro v0.76.5
              Fast - Scalable - Integrated

r - reload the app
d - open developer menu
i - run on iOS
a - run on Android

node:events:491
      throw er; // Unhandled 'error' event
      ^

TypeError: resp.asserted-states is not iterable
    at Object.onSubscribe [as cb] (D:\Sources\Personal\AwesomeProject\node_modules\metro-file-map\src\watchers\WatchmanWatcher.js:174:31)
    at BunserBuf.<anonymous> (D:\Sources\Personal\AwesomeProject\node_modules\fb-watchman\index.js:103:15)
    at BunserBuf.emit (node:events:513:28)
    at BunserBuf.process (D:\Sources\Personal\AwesomeProject\node_modules\bser\index.js:292:10)
    at D:\Sources\Personal\AwesomeProject\node_modules\bser\index.js:247:12
    at process.processTicksAndRejections (node:internal/process/task_queues:77:11)
Emitted 'error' event on WatchmanWatcher instance at:
    at Client.<anonymous> (D:\Sources\Personal\AwesomeProject\node_modules\metro-file-map\src\watchers\WatchmanWatcher.js:107:12)
    at Client.emit (node:events:513:28)
    at BunserBuf.<anonymous> (D:\Sources\Personal\AwesomeProject\node_modules\fb-watchman\index.js:111:12)
    at BunserBuf.emit (node:events:513:28)
    at D:\Sources\Personal\AwesomeProject\node_modules\bser\index.js:249:12
    at process.processTicksAndRejections (node:internal/process/task_queues:77:11)

Node.js v18.16.1

解决方案 #

• 升级Watchman到最新版本：该错误多由Watchman版本与Metro不兼容导致，Windows环境安装最新版Watchman后，重启终端再执行npm start。
• 强制Metro使用Node文件监听替代Watchman：在项目根目录创建metro.config.js，添加以下配置：

module.exports = {
  watchFolders: [__dirname],
  watcher: 'node',
};

保存后重新启动Metro。

• 清除项目缓存：执行npx react-native start --reset-cache，或删除node_modules、package-lock.json后重新执行npm install，再启动Metro。

内容的提问来源于stack exchange，提问作者Hans Yulian