在这种情况下，您调用fetchSignInMethodsForEmail获取与此电子邮件关联的IDP.这将返回带有apple.com提供程序ID的列表.您通知用户他们需要使用Apple登录该帐户.

In that case, you call fetchSignInMethodsForEmail to get the IdPs associated with this email. That will return a list with apple.com provider ID. You inform the user that they need to sign in with Apple to that account.

展望未来，他们将需要使用Apple登录.使用这两种方法的唯一方法是在使用电子邮件/密码注册之后以及在使用Apple登录之前，是否通过电子邮件验证(通过电子邮件验证).验证帐户后，Apple凭据会在登录时自动合并，并且密码会保留在帐户中.

Going forward they would need to use Apple sign-in. The only way to use both is if you verify the email (via email verification) after they sign up with email/password and before they sign in with Apple. When the account is verified, the Apple credential is merged automatically on sign-in and the password is kept on the account.