🐛 fix: nullptr errors in NextAuth adapter (#4960)

* 🐛 fix: nullptr errors in adapter

* ✅ test: pass tests

src/database/server/models/__tests__/nextauth.test.ts

@@ -146,6 +146,39 @@ describe('LobeNextAuthDbAdapter', () => {
           await serverDB.query.users.findMany({ where: eq(users.id, anotherUserId) }),
         ).toHaveLength(1);
       });
+
+      it('should create a user if id not exist even email is invalid type', async () => {
+        // In previous version, it will link the account to the existing user if the email is null
+        // issue: https://github.com/lobehub/lobe-chat/issues/4918
+        expect(nextAuthAdapter).toBeDefined();
+        expect(nextAuthAdapter.createUser).toBeDefined();
+
+        const existUserId = 'user-db-1';
+        const existUserName = 'John Doe 1';
+        // @ts-expect-error: createUser is defined
+        await nextAuthAdapter.createUser({
+          ...user,
+          id: existUserId,
+          name: existUserName,
+          email: Object({}), // assign a non-string value
+        });
+
+        const anotherUserId = 'user-db-2';
+        const anotherUserName = 'John Doe 2';
+        // @ts-expect-error: createUser is defined
+        await nextAuthAdapter.createUser({
+          ...user,
+          id: anotherUserId,
+          name: anotherUserName,
+          // @ts-expect-error: try to assign undefined value
+          email: undefined,
+        });
+
+        // Should create a new user if id not exists and email is null
+        expect(
+          await serverDB.query.users.findMany({ where: eq(users.id, anotherUserId) }),
+        ).toHaveLength(1);
+      });
     });
 
     describe('deleteUser', () => {

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

@@ -53,7 +53,10 @@ 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 = email.trim() ? await UserModel.findByEmail(serverDB, email) : undefined;
+      let existingUser =
+        email && typeof email === 'string' && email.trim()
+          ? await UserModel.findByEmail(serverDB, email)
+          : undefined;
       // If the user is not found by email, try to find by providerAccountId
       if (!existingUser && providerAccountId) {
         existingUser = await UserModel.findById(serverDB, providerAccountId);
@@ -169,7 +172,10 @@ export function LobeNextAuthDbAdapter(serverDB: NeonDatabase<typeof schema>): Ad
     },
 
     async getUserByEmail(email): Promise<AdapterUser | null> {
-      const lobeUser = email.trim() ? await UserModel.findByEmail(serverDB, email) : undefined;
+      const lobeUser =
+        email && typeof email === 'string' && email.trim()
+          ? await UserModel.findByEmail(serverDB, email)
+          : undefined;
       return lobeUser ? mapLobeUserToAdapterUser(lobeUser) : null;
     },