Angular Promises and Chaining: How to break a chain if it has business data errors

Question

I thought that I had this all figured out on previous projects through the years.. Apparently not.

Goal : Take Service that calls other Services and if there is any

Answer 1

To prevent a rejection handler from converting a rejected promise to a fulfilled promise it is important use a throw statement in the rejection handler:

var getSubmit = function (request) {
    return SparkRequestService
        .submitRequest(request)
        .then(
            function (resData) {
                console.log("resData", resData);
                enrollmentService.resetEnrollment();
                return resData;
            }, 
            function (errorResponse) {
                console.log('error');
                //IMPORTANT
                //throw to chain rejection
                throw errorResponse;
            }
        );
}

When a function omits a return or throw statement, the function returns a value of undefined. This will convert a rejected promise to a fulfilled promise that resolves with a value of undefined.

---

Problem is that ... it is a business error wrapped up in a return object

To convert a fulfilled promise to a rejected promise, use a throw statement.

this.submitEnrollment = function (enrollment) {
    var promise = getSubmit(requestData);
    var newPromise = promise.then(function(response) {
         if (response.data.hasErrors) {
             console.log(response.data.errorList);
             response.data.errorList.push("submitEnrollent: Rejected"); 
             //THROW to create rejection
             throw response;
         } else {
             //RETURN response to chain success
             return response;
         }
    });
    return newPromise;
}

When a promise is converted to a rejection, all subsequent success handlers in the chain will be skipped. The chain will be followed until a rejection handler is found.