From: Tab Atkins Jr. [[email protected]]
> I think you're making this far too complicated. It's much simpler than this:
I disagree. An abstraction boundary gets broken. Consider:
```js
function getUser1() {
return doXHR("/user.json");
}
function getUser2() {
return { "name": "domenic" };
}
function getUser3() {
return doXHR("/user.json").then(function (user) {
user.metadata = "<meta> tags are old school";
});
}
```
Here, `getUser1()` returns a cancellable promise, but `getUser2()` does not,
even though they should have the same semantics. Worse, `getUser3()` isn't
cancellable, even though it was originally derived from an XHR. Trying to fix
the `getUser3()` case is what takes you down the slope of complex additional
semantics.
Much better would be if a hypothetical future XHR utility returned a `{
promise, abort }` object, with no logical connection between the `abort` and
the `promise` (besides maybe rejecting the promise with a well-known error).
This seems much better than trying to make a general cancellation concept for
promises and overloading them with additional semantics about the operation
being performed.
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