Fix 592/1699 prevent route change start

[sylvain-hamel]

Hi, this is my first PR ever so please let me know if did not do things the right way. I signed the CLA.

It's my attempt at fixing: #1699 and #592

This change adds support to calling preventDefault() on $route's $routeChangeStart event in order to cancel a change of route while leaving the browser's Url to its new location.

This is different from calling event.preventDefault() on $location's $locationChangeStart because that reverts the browser's Url to its last Url.

Basic usage

$rootScope.$on('$routeChangeStart', function(event, next, current) {
  event.preventDefault();
});

Example: Blocking a specific route change

Setup routes:

$routeProvider.when('/Book/new', { path: '/Book/new', templateUrl: 'partials/book.html', controller: 'BookControler'});
$routeProvider.when('/Book/:d',  { path: '/Book/:d', templateUrl: 'partials/book.html', controller: 'BookControler'});

As you can see, I added a path attribute to my routes in order to compare them when $routeChangeStart will be fired. You could instead give a name such as "New Book" and "Existing Book" to your routes and compare using names.

Cancel route:
In a controller, cancel route change when going from /Book/new to /Book/:d:

$rootScope.$on('$routeChangeStart', function(event, next, current) {
  if (current && current.path === "/Book/new" && next && next.path === "/Book/:d"){
    event.preventDefault();
  }
});

---

What do you think about this solution? Do you see any potential conflicts with other parts? Can you think of additional test cases I should write?

[petebacondarwin]

Hi @redhotsly
Thanks for making this pull request.

You are basically trying to solve the same problem as was rejected in a previous PR: #2398 (comment). The router is not designed to become out of sync with the URL and providing this functionality could well cause that.

Closing for now.

[sylvain-hamel]

Hi @petebacondarwin,
Thanks for reviewing my PR. I'm indeed trying to solve the same issue. I read your comments on PR #2398. Can we talk/chat about this? There has been many +1 on those issues. I think it's worth taking the time to think about a good solution.
Thanks