Unable to throw errors in ApolloServer, unhandled promise rejection when catching an error to Cognito

Question

Creating my first User Register resolver for the GraphQL API.

I'm having trouble getting the error response from the Cognito API when I hit it from within the resolver.

The error log looks like this and will correspond to the resolver code below.

{ data: { registerUser: null } }
error is here
{ code: 'UsernameExistsException',
  name: 'UsernameExistsException',
  message: 'An account with the given email already exists.' }
error is here
{ code: 'UsernameExistsException',
  name: 'UsernameExistsException',
  statusCode: 400,
  message: '400' }

I've made sure of the following: - The resolver is being hit from the sandbox and client. - I've configured ApolloServer to formatResponses and Errors

CONFIGURATION CODE

const server = new ApolloServer({
typeDefs: [rootSchema, ...schemaTypes],
resolvers: merge({}, user),
async context({ req }) {
  const user = await authenticate(req)
  return { user }
},
formatResponse: response => {
        console.log(response);
        return response;
 },
formatError: error => ({
         message: error.message,
     state: error.originalError && error.originalError.state,
        locations: error.locations,
        path: error.path,
    })

});

const registerUser = (_, args, ctx) => {
var attributeList = [];
console.log('args')
console.log(args)

var params = {
    ClientId: "config.clientId",
    Password: args.user.password,
    Username: args.user.username,
    UserAttributes: attributeList
}
    userPool.signUp(args.user.email, args.user.password, attributeList, null, function(err, result){
        if (err) {
            console.log('error is here')
            console.log(err);
            throw new Error(err.message);
        }

        if(result) {
            console.log('result is here')
            console.log(result)
            cognitoUser = result.user;

        }

    }).catch(function(error) {
        console.log('error is below');
        console.log(error);
        return error;
    })

}

Two things are preventing me from moving forwards. When I leave out the catch block off the userPool promise I simply get no error at all, the error is not being thrown from inside the signUp function.

If I throw any error at all from within my resolver (whether its within the callback or the catch block) I get the following error.

at process._tickCallback (internal/process/next_tick.js:160:7)
(node:28342) UnhandledPromiseRejectionWarning: Unhandled promise 
rejection. This error originated either by throwing inside of an async 
function without a catch block, or by rejecting a promise which was not 
handled with .catch(). (rejection id: 1)
(node:28342) [DEP0018] DeprecationWarning: Unhandled promise rejections 
are deprecated. In the future, promise rejections that are not handled 
will terminate the Node.js process with a non-zero exit code.

I would like to get the following error to be returned to the Sandbox/Requestor

{ data: { registerUser: null } }
error is here
{ code: 'UsernameExistsException',
  name: 'UsernameExistsException',
  message: 'An account with the given email already exists.' }

Thanks for your help.

Welcome to Stack Overflow. I don't think you need to throw an error, you should return data with an error code — Mikkel
@Mikkel - thank you! when I simply return the err, it doesn't make its way to the response. — techromantic

techromantic techromantic · Accepted Answer · 2018-12-30T21:13:32

Figured it out. AWS APIs are limited to Callback implementation. Wrap your callback as a promise - then chain that promise to throw as needed.

Unable to throw errors in ApolloServer, unhandled promise rejection when catching an error to Cognito

1 Answers