$q.reject and handling errors in AngularJS chained

I'm having trouble understanding a basic concept of error handling with chaining promises. In order to learn the rules, I have written a simple example, guessing what the result will be. But unfortunatly it doesn't behave as I though it will. I have read multiple articles about the subject but perhaps can't I get details because of my poor english language.

Anyway, here is my code :

    var promiseStart = $q.when("start");
    var promise1 = promiseStart.then(function() {
            return Serviceforpromise1.get();
    });
    var promise2 = promise1.then(function(data1)
    {
            return Serviceforpromise2.get(data1);
    },function(error)
    {
            return $q.reject();
    });
    var promiseend = promise2.then(function(data2)
    {
            return data2;
    },function(error)
    {
            return error;
    });
    return promiseend;

Well I know that it can be way better coded but it's just for the purpose. Here is the code of Serviceforpromise1 function :

    function Serviceforpromise1()
    {
            ...
            return $http.get(*whatever*).then(function (data){
                return data;
            },function(error)
            {
                return $q.reject();
            });
    }

Consider only the case of Serviceforpromise1's failure. A $q.reject is sent back to main chain so I'm waiting the error callback of "promise1 .then(" to be called and it worked as expected. I decided for the example to transfert the error to the "promise2 .then" so in this error callback I added the line return $q.reject(); But it never reached the second error callback (the "promise2 .then" one) and I don't understand why (like Serviceforpromise1, I returned a rejected promise !)

I will be happy to deeply understand what is happening here. Thanks for your help.

Your understanding is correct, and the problem appears to lie somewhere in the way you are trying to observe this behavior (in something you haven't shown us).

If you return a rejected promise from either a success or error handler in then(), then the promise returned by then() will resolve to a rejected promise. Observe:

angular.module('app', [])
    .controller('C', [
    '$q',

function ($q) {
    var promiseStart = $q.when("start");
    var promise1 = promiseStart.then(function (value) {
        console.log('Got a value:', value);
        return $q.reject('Error!');
    });

    var promise2 = promise1.then(function (data1) {
        return "Got some stuff";
    }, function (error) {
        console.log("Caught an error:", error);
        return $q.reject('New error');
    });

    var promiseend = promise2.then(function (data2) {
        return data2;
    }, function (error) {
        console.log('Caught an error:', error);  // <-- this is logged to the console
        return error;
    });

    return promiseend;
}]);

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.min.js"></script>
<div ng-app='app' ng-controller='C'></div>

One thing to note here is that in that last handler, you are returning the error variable, and not throwing an exception or returning a rejected promise. So in this case, promiseend will successfully resolve with the value of that error variable.