🐛 fix: wrong email linking

src/libs/next-auth/adapter/index.ts

@@ -8,8 +8,8 @@ import { and, eq } from 'drizzle-orm';
 import type { NeonDatabase } from 'drizzle-orm/neon-serverless';
 import { Adapter, AdapterAccount } from 'next-auth/adapters';
 
-import { UserModel } from '@/database/server/models/user';
 import * as schema from '@/database/schemas';
+import { UserModel } from '@/database/server/models/user';
 import { merge } from '@/utils/merge';
 
 import {
@@ -53,7 +53,13 @@ export function LobeNextAuthDbAdapter(serverDB: NeonDatabase<typeof schema>): Ad
     async createUser(user): Promise<AdapterUser> {
       const { id, name, email, emailVerified, image, providerAccountId } = user;
       // return the user if it already exists
-      let existingUser = await UserModel.findByEmail(serverDB, email);
+      let existingUser;
+      // Only find by email if email is provided
+      // fix for: https://github.com/lobehub/lobe-chat/issues/4918
+      // side impact: no email restrictions, aka anonymous login,
+      //                discuss at https://github.com/lobehub/lobe-chat/discussions/4844
+      if (email.trim().length > 0)
+        existingUser = await UserModel.findByEmail(serverDB, email.trim());
       // If the user is not found by email, try to find by providerAccountId
       if (!existingUser && providerAccountId) {
         existingUser = await UserModel.findById(serverDB, providerAccountId);