Remove transition.wait, use callbacks instead

[mjackson]

This commit also removes our dependency on when.js and introduces
a callback argument in transition hooks. Users are expected to call
callback(error) when they're finished doing async stuff. If they
don't have a callback in their argument list, we automatically call
the callback for them for backwards compat.

Fixes #273
Fixes #631

I have mixed feelings about this PR. Part of me wishes that everyone would get on the same page, realize how cool promises are, use webpack, and be happy. But hey, at least we get:

1. smaller file size
2. 1 less dependency
3. easier compat with browserify

[ryanflorence]

not that I dislike promises, but this is great 👍

[ryanflorence]

I know 3 is the magic number, but what is this 3 all about?

[ryanflorence]

oh nvm, args length, I was thinking we were collecting hooks or something ...

[mjackson]

I'll make the comment clearer.

[ryanflorence]

File size is 7.7kb now, saves us ~3k. I think that and the other things you've noted are worth this change:

transition.wait(promise());
promise().then(callback);

I can't find an objective reason the wait API is better either.

[raine]

typo

[mjackson]

Thanks :)

[gaearon]

I didn't realize we can check arity. I'm on board with this!

[mjackson]

@rpflorence @gaearon We should cut another minor release with this change. Anything else you wanna get in?

[gaearon]

@mjackson I'd love to see replaceRoutes:

      replaceRoutes: function (children) { 
        namedRoutes = {};
        routes = [];
        this.addRoutes(children);
      },

[ryanflorence]

I'll get a release out today, it's a breaking api change so we'll be at 0.12

[JFusco]

So how would you handle a transition.redirect() when doing async/promise calls? Seems that the redirect gets ignored when trying to do something like this:

statics: {
    willTransitionTo: function (transition, params) {
        something.call(somePath())
            .then(function(){
                transition.redirect('accessDenied');
            });
    }
}

@mjackson Thanks for your hard work! Looking forward to future releases

[JFusco]

Sorry if I was not clear in my above question - since the removal of .wait(), what would be the equivalent to this?

statics: {
    willTransitionTo: function (transition, params, query) {
      transition.wait(
        checkAuthAndStoreItSomewhere().then(function (auth) {
          if (auth == null)
            transition.redirect('login');
        });
      );
    }
}

[gaearon]

@JFusco

I think something like

statics: {
    willTransitionTo: function (transition, params, query, callback) {
      checkAuthAndStoreItSomewhere().then(function (auth) {
        if (auth == null)
          transition.redirect('login');
      }).then(callback);
    }
}

[JFusco]

Thanks @gaearon - this occurred to me this morning..just needed some sleep :)

I appreciate the quick response and the hard work...Looking forward to .13 release so I can fully support ES6 in React!