collections breaks Array.from with Iterables

[akloeber]

collections breaks Array.from with Iterables. This can be reproduced with the following code:

var obj = {};
obj[Symbol.iterator] = function() {
  var values = ['foo', 'bar'];

  return {
    next: function() {
      var done = values.length === 0;
      var value = done ? undefined : values.shift();

      return {
        value: value,
        done: done
      };
    }
  };
};

console.log('before collections load:', Array.from(obj));
require('collections/sorted-map');
console.log('after collections load:', Array.from(obj));

Output:

$ node test.js
before collections load: [ 'foo', 'bar' ]
after collections load: []

Environment:
collections v5.0.6
node v4.4.7
Mac OS X 10.12.2

[a-x-]

It implicitly breaks our code too (i had got 4 debug hours) :(

[FrozenPrincess]

Yeah, I lost the better part of a day to this too. It broke some code completely unrelated to anything near the collections stuff, and ended up being a real bitch to track down.

Blindly overwriting Array.from seems like a bad idea, but to do it with a non-conformant implementation really blows my mind.

[marchant]

This Array.from may have been written before the current one even existed or was final. Iterators changed in the past 5 years. So if you're happy with the rest of this library, give the author(s) some credits there. Thanks @a-x- for the PR, it's a step in the right direction to use the native implementation when available, but the shim has to be re-aligned and do what native Array.from does, contributions welcomed!

[kriskowal]

This issue is addressed with Collections version 2. However, this is not backward-compatible with the MontageJS install base, so it is not default. npm install collections@2 to use a modern version that does no monkey patching (unless you make an array instance mutations observable).