FireStore与Firebase Auth配置冲突：重复应用实例错误解决方案咨询

问题描述 #

发现FireStore的messagingSenderId与Firebase Auth的messagingSenderId不同，于是拆分为两个配置进行初始化，却遇到错误：
FirebaseError: Firebase: Firebase App named '[DEFAULT]' already exists with different options or config (app/duplicate-app)

相关代码：

// Import the functions you need from the SDKs you need
import { initializeApp, getApps, getApp } from "firebase/app";
import { getAuth } from "firebase/auth";
import { getFireStore } from "@firebase/firestore";

// TODO: Add SDKs for Firebase products that you want to use
// https://firebase.google.com/docs/web/setup#available-libraries
// Your web app's Firebase configuration
const firebaseConfig = {
  apiKey: "someKey",
  authDomain: "someDomain",
  projectId: "same ID",
  storageBucket: "same storage bucket",
  messagingSenderId: "Different messagingSenderId",
  appId: "same ID",
};

const fireStoreConfig = {
  apiKey: "sameKey",
  authDomain: "sameDomain",
  projectId: "same ID",
  storageBucket: "same storage bucket",
  messagingSenderId: "Different messagingSenderId",
  appId: "same ID",
};

// Initialize Firebase
let app = {};
getApps().length === 0
  ? (app = initializeApp(firebaseConfig))
  : (app = getApp());

storeApp = initializeApp(fireStoreConfig);

export const auth = getAuth(app);
export const db = getFireStore(storeApp);

请问是否应该分开配置，或是有更优的解决方式？

解决方案 #

1. 核心结论：完全不需要分开配置 #

messagingSenderId是Firebase Cloud Messaging（FCM）的专属配置，和Firebase Auth、FireStore的核心功能没有关联。同一个Firebase项目下，Auth和FireStore共享同一套应用配置即可，messagingSenderId的差异大概率是配置复制时的失误，或是FCM配置更新导致，但不会影响Auth和FireStore的正常运行。

2. 修正后的代码 #

只需初始化一次默认Firebase应用，分别获取Auth和FireStore实例：

import { initializeApp, getApps, getApp } from "firebase/app";
import { getAuth } from "firebase/auth";
import { getFireStore } from "@firebase/firestore";

// 使用统一的项目配置
const firebaseConfig = {
  apiKey: "someKey",
  authDomain: "someDomain",
  projectId: "same ID",
  storageBucket: "same storage bucket",
  // 任选一个messagingSenderId即可，或使用项目最新的FCM配置
  messagingSenderId: "your-project-messaging-sender-id",
  appId: "same ID",
};

// 初始化默认应用（避免重复初始化）
const app = getApps().length === 0 ? initializeApp(firebaseConfig) : getApp();

// 从同一应用实例获取Auth和FireStore
export const auth = getAuth(app);
export const db = getFireStore(app);

3. 若确实需要多应用初始化（特殊场景） #

如果你的需求是连接不同Firebase项目的Auth和FireStore，才需要初始化多个应用，此时必须给第二个应用指定唯一名称：

// 初始化默认应用（用于Auth）
const authApp = getApps().length === 0 ? initializeApp(firebaseConfig) : getApp();
// 初始化第二个应用（指定名称"firestore-app"）
const storeApp = initializeApp(fireStoreConfig, "firestore-app");

export const auth = getAuth(authApp);
export const db = getFireStore(storeApp);

但这种场景在你的问题中完全没必要，属于过度设计。

内容的提问来源于stack exchange，提问作者Mustafa Walid