ES6-Shim should not return Symbol.iterator instead of Array in Firefox when using with

[timcosta]

See https://jsfiddle.net/dfqve80a/3/ in Firefox and Chrome for an example of the problem

Essentially, if you load es6-shim and then run the following code, the output should be [1,2,3] instead of Symbol.iterator.

var fxn = function(values) {
    with(values) {
        return values;
    }
}
console.log( fxn([1,2,3]) ); // Symbol.iterator in Firefox

This may also be affecting IE, however I do not have a version of IE handy to test with currently.

[ljharb]

This relates to the behavior of Symbol.unscopables, which browsers don't usually implement correctly, and is unshimmable. Try the same with "values" and "entries" - you'll see it's the actual function it's pulling off of the array.

At any rate this isn't caused nor exacerbated by es6-shim, and is impossible to fix in JS.

[ljharb]

(This shouldn't come up in real code, though, because nobody should ever be using the with statement for any reason)

[timcosta]

Unfortunately ExtJs 3.1.1 uses the exact function in the JsFiddle. Thanks for the information though, its going to be quite valuable while we work to solve this.

[ljharb]

I would highly discourage using any libraries or frameworks that use the with statement in 2015. ExtJS is up to 6.0, so if you're on 3.1.1 you may wish to upgrade - 3.0 came out in 2009, and as such, is ancient.

[timcosta]

You don't have to tell me that haha. We are working to get away from it, but sometimes there are things higher up on the priority list.

[ljharb]

I can't imagine what would be higher on the priority list than using 6 year old outdated software that is broken in modern browsers, but it's not up to me I guess :-)

[timcosta]

If it ain't broke and the clients want other things, it's not high priority haha. Now that it has a known fault it'll likely be reevaluated.

[rwaldron]

ExtJs is the exact reason that unscopables exists—for the exact code that was cited here.

[ljharb]

@rwaldron aha, i had a hunch that was the case. does that mean that Firefox should have a bug filed re unscopables?