NextAuth与Firebase集成报错：Cannot use import statement outside a module

核心问题分析 #

你的代码存在几处关键问题，导致认证流程失败：

1. Firebase初始化时调用getApps.length错误，需调用getApps()获取应用列表后再判断长度
2. 混合使用Firebase Compat SDK与模块化SDK，易引发冲突
3. NextAuth的Firestore适配器传入配置对象而非已初始化的Firestore实例，可能导致重复初始化错误

修改后的代码 #

1. 修正firebase.js

import { initializeApp, getApps, getApp } from 'firebase/app';
import { getFirestore } from 'firebase/firestore';
import { getStorage } from 'firebase/storage';

export const firebaseConfig = {
    apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY,
    authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
    projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
    storageBucket: process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
    messagingSenderId: process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
    appId: process.env.NEXT_PUBLIC_FIREBASE_APP_ID,
    measurementId: process.env.NEXT_PUBLIC_FIREBASE_MEASUREMENT_ID
};

// 修复getApps调用方式，避免重复初始化应用
export const app = getApps().length > 0 ? getApp() : initializeApp(firebaseConfig);
export const firestore = getFirestore(app);
export const storage = getStorage(app);

2. 修正[...nextauth].js

import NextAuth from "next-auth";
import DiscordProvider from 'next-auth/providers/discord';
import { FirestoreAdapter } from "@next-auth/firebase-adapter";
import { firestore } from "../../../lib/firebase";

export default NextAuth({
    providers: [
        DiscordProvider({
            clientId: process.env.DISCORD_ID,
            clientSecret: process.env.DISCORD_SECRET
        }),
    ],
    // 传入已初始化的Firestore实例，避免重复初始化
    adapter: FirestoreAdapter(firestore),
    // 可选：使用JWT会话策略，减少Firestore依赖
    session: {
        strategy: "jwt"
    }
})

额外检查项 #

• 确认所有环境变量（NEXT_PUBLIC_FIREBASE_*、DISCORD_ID、DISCORD_SECRET）在.env.local文件中配置正确，无拼写错误
• 确保Firebase项目已启用Firestore数据库，开发环境可暂时设置数据库规则为：

  rules_version = '2';
  service cloud.firestore {
    match /databases/{database}/documents {
      match /{document=**} {
        allow read, write: if true;
      }
    }
  }
  

  生产环境需调整为安全规则
• 检查next-auth和@next-auth/firebase-adapter版本兼容性，建议使用最新稳定版
• 移除package.json中的"type": "module"，Next.js默认支持ES模块，无需额外配置

内容的提问来源于stack exchange，提问作者Ram