How do you return validation errors ?

[thecritic]

First of all, thank you for creating this gem!

I created the auth providers for Google/FB as shown in the Wiki, however, there is a use case where a user has already signed up with a normal account in the past and then tries to log in with Facebook/Google where the email already exists. This would throw an ActiveRecord::RecordInvalid exception upon account creation, how am I supposed to get that into the response to let the user know that an account with that email already exists ?

Here is the code:

doorkeeper.rb

resource_owner_from_assertion do
    provider = params[:provider]
    case provider
    when "google"
      g = ExternalAuth::Google.new(params[:assertion])
      g.get_user!
    when "facebook"
      f = ExternalAuth::Facebook.new(params[:assertion])
      begin
        f.get_user!
      rescue ActiveRecord::RecordInvalid => e
        #what happens here ? 
      end 
      end
    end
  end

facebook_auth.rb

def get_user!
  if user_data.present?
    user = User.where(fb_id: user_data["id"]).first
    if user.blank?
      user = User.new(
        remote_profile_image_url: image["data"]["url"], 
        fb_id: user_data["id"], 
        firstname: user_data["first_name"], 
        lastname: user_data["last_name"], 
        email: user_data["email"]
      )
      user.password = SecureRandom.hex
      user.save!
    end
      user
  else
    nil
  end
end

[matfiz]

I guess the easiest would be to raise an instance of DoorkeeperError (aka StandardError), eg:
raise Doorkeeper::Errors::DoorkeeperError.new('email already exists')

[matfiz]

Or another idea, however I do not know if it will serve your case. Why not to check the existing users against fb_id OR email? Something like

user=User.where('fb_id=? or email=?',user_data["id"],user_data["email"]).first

In such a way, you can match and log in the user by email, possibly updating the fb_id if it is empty.

[thecritic]

Thanks a lot @matfiz, second solution was bang on!