我正在尝试为Firebase函数设置目标部署。https://firebase.google.com/docs/cli/targets
这是firebase.json文件

{
  "functions": [{
    "target": "production",
    "source": "src/prod/functions",
    "predeploy": [
      "npm --prefix \"$RESOURCE_DIR\" run lint",
      "npm --prefix \"$RESOURCE_DIR\" run build"
    ]
  }]
}

预部署正常运行，但在部署时出现错误

functions[prod]: Finished running predeploy script.
Error: An unexpected error has occurred.

如果我转到firebase-debug.log，它会显示：

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined

将Functions文件夹放置在项目根目录下，它将正常部署。
这里缺少什么？