How to handle multiple errors in promise chain?

Question

I'm using AWS Amplify for authentication and Stripe for the payment to create sign up page.

PROBLEM: I can't find a way to combine validations for Email and password section(from AWS Amplify) with payment info section(from Stripe).

My current code creates a Stripe token and call API(with valid payment info) then handles the error message from userSignupRequest which takes care of email and password fields.

How do I validate the email and password with payment info then create account in AWS and Stripe?

  // Stripe payment process
  this.props.stripe.createToken(
    {
      email: this.state.email
    }
  ).then(result => {
    // PROBLEM: Form server validation from Stripe
    if(result.error){
      return this.setState({ errors: { errorMsg: result.error.message }, isLoading: false })
    }

    // if success, create customer and subscription with result.token.id
    const apiName = 'NameOfAPI';
    const path = '/stripe/signup';
    let myInit = {
      body: {
        "stripeToken": result.token.id,
        "email": this.state.email
      }
    }

    API.post(apiName , path, myInit).then(reponse => {
      this.props.userSignupRequest(this.state.email, this.state.password, reponse).then(user => {
        this.setState({
          confirmAccount: true,
          isLoading: false,
          userEmail: this.state.email,
          errors: {}
        })
        this.props.history.push('/signup#confirm-account')
      }).catch(err => {
        // PROBLEM: Form server validation 
        this.setState({ errors: { errorMsg: err.message }, isLoading: false })
      })

    }).catch(err => {
      console.log(err)
      this.setState({ errors: { errorMsg: err }, isLoading: false })
    });

  })

Answer 1

It seems like we have a very similar stack. My solution was to handle everything server-side. You'll need to give your lambda functions the appropriate IAM permissions to access Cognito. The code below is a little long. I use async/await, which really cleans things up for me. You'll need to use Lambda with node 8 to use async/await though.

I validate that everything matches the right format client-side (i.e. emails are really emails, passwords are the right length). I realized the only error that could come up is an "existing user" error from Cognito. The idea is: test if the user exists before you attempt to sign the person up with Stripe. There's no way to "test" if the user's credit card is valid with Stripe. It's all or nothing. If it's valid it will go through, if not, you'll get an error. If it goes through, you can then sign up the user with Cognito, knowing you should not get an error (you've validated the email and password client-side and, you know the use doesn't already exist).

For reference, here's the aws-sdk for cognito.

const AWS = require('aws-sdk');
const cognito = new AWS.CognitoIdentityServiceProvider({
  region: "region",
  userPoolId: "cognito_user_pool_id",
});

module.exports.signUpUser = (payload) => {
  const usernamePayload = {
    UserPoolId: "cognito_user_pool_id",
    Username: payload.email,
  };

  // I use emails for usernames.

    new Promise((resolve, reject) => {
      cognito.adminGetUser(usernamePayload, (error, response) => {
        if (error && error.code === 'UserNotFoundException') {
          resolve(false);
        } else if (error) {
          reject(error);
        } else {
          // if adminGetUser doesn't fail, it means the username exists
          resolve(true);
        }
      });
    }).then((usernameExists) => {
      if (!usernameExists) {
        // run stripe API stuff
        // always run before sign up below to catch stripe errors
        // and return those errors to client
        // before you sign up the user to Cognito

        // since you've already verified the user does not exist
        // it would be rare for an error to come up here
        // as long as you validate passwords and emails client-side
        const signUpPayload = {
          ClientId: "cognito_user_pool_client_id",
          Username: payload.email,
          Password: payload.password,
          UserAttributes: [
            {
              Name: 'email',
              Value: payload.email,
            },
          ],
        };

          new Promise((resolve, reject) => {
            cognito.signUp(signUpPayload, (error, response) => {
              if (error) {
                reject(error);
              } else {
                resolve(response);
              }
            });
          }).catch((error) => {
            // you should hopefully encounter no errors here
            // once you get everything setup correctly
            console.log(error);
          })
      } else {
        // means username already exists, send error to client
        // saying username exists
      }
    }).catch((error) => {
      // may want to dispatch this error to client
      console.log(error);
    });

  return null;
};