Why RSVP Deferred produces error when promise is called twice

Question

Why RSVP Deferred produces an error when the promise is called twice?

It seems that there is a difference between deferred.promise.then().finally() and deferred.promise.then(); deferred.promise.finally(). Why?

RSVP.on('error', function(reason) {
  console.log('Error: ' + reason);
});

var deferred = RSVP.defer();
var deferred2 = RSVP.defer();
var deferred3 = RSVP.defer();
var promise3 = deferred3.promise;

deferred.promise.then(function() {
  console.log('Resolved');
}, function() {
  console.log('Rejected');
}).finally(function() {
  console.log('Finally');
});

deferred2.promise.then(function() {
  console.log('Resolved2');
}, function() {
  console.log('Rejected2');
});

deferred2.promise.finally(function() {
  console.log('Finally2');
});

promise3 = promise3.then(function() {
  console.log('Resolved3');
}, function() {
  console.log('Rejected');
});

promise3.finally(function() {
  console.log('Finally3');
});


deferred.reject('Reject!');
deferred2.reject('Reject2!');
deferred3.reject('Reject3!');

<script src="https://cdnjs.cloudflare.com/ajax/libs/rsvp/4.8.1/rsvp.js"></script>

EDIT: I found out how to fix the issue. See the Deferred3 in the code.

Answer 1

I found that promise.then() (and other methods) returns a modified promise so you have to chain the then, finally, catch... methods or you have to save the promise each time.

RSVP.on('error', function(reason) {
  console.log('Error: ' + reason);
});

var deferred = RSVP.defer();
var promise = deferred.promise;

promise = promise.then(function() {
  console.log('Resolved');
}, function() {
  console.log('Rejected');
});

promise.finally(function() {
  console.log('Finally');
});


deferred.reject('Reject!');

<script src="https://cdnjs.cloudflare.com/ajax/libs/rsvp/4.8.1/rsvp.js"></script>