[added] Router.AsyncState mixin

[mjackson]

This is just a start on the work needed to eventually support server-side rendering (see #57). The other things needed are:

1. A renderRoutesToString(routes, path) method
2. Actually mixing this in to Route (or a RouteHandler mixin, see Make Route more extensible #65)

Ideally we can merge these pieces one at a time and make a release when they're all ready.

[ryanflorence]

what a nice treat to my inbox before going to bed!

[ryanflorence]

should probably note here that state will be automatically set to the resolved value, calling setState is just for additional state related to the async operation.

[sophiebits]

The separate setState function weirds me out a bit. I wonder if we can get by without it.

[ryanflorence]

hmm, maybe we should bring in sinon or something else to fake timers (later, this is fine).

[ryanflorence]

@spicyj how else would you handle the streaming use-case? (But yeah, it is a little weird.)

[sophiebits]

@rpflorence You wouldn't be able to, but is that common? I can't recall a time I've wanted to do that, and it seems to me that it might be easily confused with this.setState.

[ryanflorence]

I have wanted to be able to update the progress of a long xhr call in ember's router and couldn't, and I know @mjackson has this exact need (streaming) in something he's working on.

[sophiebits]

If only we had Observable in JS… (https://docs.google.com/file/d/0B4PVbLpUIdzoMDR5dWstRllXblU/edit?pli=1).

I don't have any better ideas right now for the streaming use case.

[ryanflorence]

@spicyj lets just not talk about it much, and if anybody gets a better idea we'll implement it quickly. I'd rather have something weird than nothing at all.

I might even do getInitialAsyncState: function(params, query, soWeird){}

[mjackson]

@spicyj If it makes you feel any better, the setState function is only sugar over the real component's this.setState (we only do a small check to make sure this.isMounted() because it's async). But it's the simplest thing that could work here, and the one that will be most familiar to React devs.

[mjackson]

Anyway, I anticipate that the most common usage will be to just return a hash. This looks exactly like getInitialState, the only difference being the values can be promises.

getInitialAsyncState: function (params, query) {
  return {
    user: getUser(params.userID)
  };
}

[mjackson]

Updated the docs according to @rpflorence feedback and rebased. Let me know if there are any other concerns.

[ryanflorence]

This is fantastic. Can you smell v1.0?

[mjackson]

:) Please feel free to click the merge button.

Yeah, 1.0 is just around the corner!