Change setProperty and morph to remove an undefined or NaN attr value

[mixonic]

Open for debate. Maybe this should be part of another layer in Ember. IMO it is ok here.

Ember expects setting an attribute binding to undefined or NaN to remove the attribute entirely. This follows that logic.

[oneeman]

Does updateAttributeNS also need to be updated? And this might be a good opportunity to DRY it up a bit as well (e.g. L170-178 and L184-192 in dom-helper.js, but maybe also the check for remove attribute between there and attr-morph).

As for whether it belongs here, maybe someone else can chime in. I don't know the ember code yet, so I wouldn't know what should go where.

[mixonic]

The Ember side is here: emberjs/ember.js#10186. This is updated to test and work with namespace attrs. And be a bit more DRY.

[mixonic]

Phantom has no native isNaN. function isNan(x) { return x !== x } is a possible poly-fill.

[mixonic]

After discussion with @rwjblue I've dropped the NaN check.

In Ember, I'm leaving the NaN value behavior undefined: https://github.com/emberjs/ember.js/pull/10186/files#diff-f7920bfff32661282a5d9c883cc26641L43

[oneeman]

Thanks!

[rwjblue]

@mixonic - Let me know when you need a version cut for the Ember updates.