Declaring Firebase auth trigger error: "TypeError: Cannot read properties of undefined (reading 'user')"

Question

I am trying to create a firebase function that essentially listens to an event where a user created using the firebase authentication and then it creates a new record in the real time database where the user ID is the record itself and it also has a permission value set to false

in run into errors when deploying, someone can help?

when I run

const functions = require("firebase-functions");
const admin = require("firebase-admin");

admin.initializeApp();

const addUserToDatabase  = (userRecord) => {
    const uid = userRecord.uid;
    const email = userRecord.email;
  
    return admin.database().ref(`/Users/${uid}`).set({
      email: email,
      permission: false
    });
  }

// This function runs when a new user is created via Firebase Authentication

module.exports = {
    addUserToDatabase: functions.auth.user().onCreate(addUserToDatabase),
  }
  

I get this error

    TypeError: Cannot read properties of undefined (reading 'user')
        at Object.<anonymous> (/Users/yanir/coding/fBCLI/functions/index.js:19:39)
        at Module._compile (node:internal/modules/cjs/loader:1554:14)
        at Object..js (node:internal/modules/cjs/loader:1706:10)
        at Module.load (node:internal/modules/cjs/loader:1289:32)
        at Function._load (node:internal/modules/cjs/loader:1108:12)
        at TracingChannel.traceSync (node:diagnostics_channel:322:14)
        at wrapModuleLoad (node:internal/modules/cjs/loader:220:24)
        at Module.require (node:internal/modules/cjs/loader:1311:12)
        at require (node:internal/modules/helpers:136:16)
        at loadModule (/Users/yanir/coding/fBCLI/functions/node_modules/firebase-functions/lib/runtime/loader.js:40:16)

package.json:

{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "scripts": {
    "serve": "firebase emulators:start --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  },
  "engines": {
    "node": "22"
  },
  "main": "index.js",
  "dependencies": {
    "firebase-admin": "^12.6.0",
    "firebase-functions": "^6.3.2"
  },
  "devDependencies": {
    "firebase-functions-test": "^3.1.0"
  },
  "private": true
}

Answer 1

The API changed in version 6 of firebase-functions with the addition of gen2 APIs for most other types of triggers (except auth, which is still on gen1). Your require statement should look like this now:

const functions = require("firebase-functions/v1");

You can see a more complete example of an auth trigger on GitHub.