Ember.A(null) now returns null instead of []

[workmanw]

Here is a pretty clear snippet that explains the issue:

// Ember 2.4.x
Ember.A(null);   // returns []

// Ember Beta
Ember.A(null);   // returns null

So what happened? It looks like this commit broke it: 586d4c6#diff-7 :(. It seems very harmless, but that code is transpiled as:

A = A = function () {
  var arr = arguments.length <= 0 || arguments[0] === undefined ? [] : arguments[0];
  return arr;
};

The problem is that because Ember.A(null) has an argument length greater than 1, it's value [null] is ultimately returned.

Unfortunately this did break a few tests in our application. Specifically with the fixture adapter, see here: https://github.com/emberjs/ember-data-fixture-adapter/blob/master/addon/index.js#L298-L300 . I believe this to be part of the public API and should be fixed. If so, I'd be happy to add a test and take care of it.

---

EDIT: As a side note, I feel like I should voice some my concern about the aforementioned commit ( 586d4c6 ). There are several other places where argValue || [] was replaced with default arguments, potentially leading to the same issue.

[mmun]

Yep. This should totally be fixed and a tested added.

Out of curiosity, which version of Ember.A(null) do you think makes more sense?

@thoov can you do a quick audit of what else might have broken?

[workmanw]

Out of curiosity, which version of Ember.A(null) do you think makes more sense?

@mmun I was just asking myself that. I read the API docs to see if they indicated one way or another, but it was still kind of ambiguous. I could probably make an argument either way.

I sometimes use Ember.A as a safety guard for functions expecting a list argument. Eg:

mapListValues(list) {
  return Ember.A(list).map(item => { /* ... */ });
})

But I could be convinced that this isn't the purpose of Ember.A.

[workmanw]

This issue was fixed with #13287 being merged in.

[rwjblue]

Thanks for catching this @workmanw!

[workmanw]

@rwjblue My pleasure!

Random Fact: I just started using ember-try to test our app against "default", "stable", "beta" and "canary". Setting up a nightly cron to run the tests against all 4 scenarios and email me of any failures. On the first night, it caught this. If I can ever muster the cycles to write a blog post, it'll be about how to do this.