I'm working on a VUE Amplify project, it's almost done, but cognito does not offer mail duplication check, so i've to do it manually, as we know AWS has some triggers i'm using PreSignUp invoking a Lambda function, my code is:

var AWS = require("aws-sdk");
const cognitoidentityserviceprovider = new AWS.CognitoIdentityServiceProvider();


exports.handler =  function(event, context, callback) {
  var params = {
    UserPoolId: "us-east-1_xxxXXXxXX",
    AttributesToGet: ["email"]
  };

  cognitoidentityserviceprovider.listUsers(params, (err, data) => {
    if (err) {
      console.log(err, err.stack);
      callback(err)        // here is the error return
    } else {
      data.Users.forEach(function(usuario) {
        if(usuario.Attributes[0].Value == event.request.userAttributes.email){
          return {};
        }
      });
      callback(event);
    }
  });
}

but I dont understand what I am doing wrong, the lambda execution returns...

Object { code: "UserLambdaValidationException", name: "UserLambdaValidationException", message: "PreSignUp failed with error [object Object]." }

Any idea?

CodePudding user response：

You need to return the event object

https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-pre-sign-up.html