Express应用与Firebase Functions混合部署报错，求解决方法

我采用如下文件目录结构开发Firebase Functions与Express混合应用：

.
└── src/
    ├── index.ts
    ├── auth/
    │   └── auth.ts
    ├── controllers/
    │   ├── user.ts
    │   └── event.ts
    ├── functions/
    │   └── email.ts
    └── models/
        ├── user-model.ts
        ├── event-model.ts
        └── email-model.ts

index.ts代码如下：

import * as admin from "firebase-admin";
admin.initializeApp();
admin.firestore().settings({ ignoreUndefinedProperties: true });

module.exports = {
  ...require("./controllers/user"),
  ...require("./controllers/event"),
  ...require("./functions/email"),
};

event.ts和user.ts遵循以下结构：

const eventApp: express.Application = express();
eventApp.use(bodyParser.json());
eventApp.use(cors({ origin: true }));
eventApp.get("/",
    isAuthenticated,
    isAuthorized({ hasRole: ["admin"] }),
    async (req: express.Request, res: express.Response) => { ... });

module.exports.events = functions.https.onRequest(eventApp);

email.ts结构：

module.exports.sendInitialInvitation = functions.firestore
.document('{collection}/{docId}')
.onCreate((snap: QueryDocumentSnapshot, context: any) => { ... });

部署时持续出现错误：

Error: Failed to load function definition from source: Failed to generate manifest from function source: TypeError: Cannot read properties of undefined (reading 'document')

删除functions文件夹及index.ts中对应引用后，部署可正常完成。请问该错误的原因是什么？如何解决？

email.ts中未导入Firebase Functions模块，导致functions变量未定义，调用functions.firestore.document()时触发Cannot read properties of undefined (reading 'document')错误。同理，user.ts和event.ts中如果也没导入functions模块，其实也存在潜在问题，只是之前删除email.ts后没暴露出来。

1. 补全模块导入
   在email.ts顶部添加Firebase Functions的导入语句：

   import * as functions from "firebase-functions";
   

   同时在user.ts和event.ts中补全所有必要的导入：

   import * as functions from "firebase-functions";
   import * as express from "express";
   import * as bodyParser from "body-parser";
   import * as cors from "cors";
   // 根据实际情况导入auth中间件（isAuthenticated、isAuthorized）
   

2. 优化导出逻辑（TypeScript推荐写法）
   原index.ts使用CommonJS的require混合ES模块导入，容易引发模块加载冲突。建议统一使用ES模块导出：

   import * as admin from "firebase-admin";
   import * as userControllers from "./controllers/user";
   import * as eventControllers from "./controllers/event";
   import * as emailFunctions from "./functions/email";
   
   admin.initializeApp();
   admin.firestore().settings({ ignoreUndefinedProperties: true });
   
   // 导出所有控制器和函数
   export const events = eventControllers.events;
   export const users = userControllers.users; // 假设user.ts导出的函数名为users
   export const sendInitialInvitation = emailFunctions.sendInitialInvitation;
   

3. 验证编译配置
   检查tsconfig.json，确保编译目标为CommonJS（Firebase Functions默认支持），关键配置如下：

   {
     "compilerOptions": {
       "module": "commonjs",
       "target": "ES2017",
       "outDir": "./lib",
       "rootDir": "./src"
     }
   }
   

   确保部署时使用编译后的lib目录文件，而非原始src文件。

内容的提问来源于stack exchange，提问作者Parth Shah