Unexpected behavior: keys() mutates the inputted array

[jwngr]

I ran into an unexpected behavior with chai that I think should be considered a bug. Here is a reduced repro of the issue which currently fails:

it('keys() should not mutate inputted array', function() {
  var expectedKeys = ['b', 'a'];
  expect({a: true, b: true}).to.have.keys(expectedKeys);
  expect(expectedKeys[0]).to.equal('b');
});

Calling keys() should be able to do the comparison without mutating the inputted array since that array could be used in later assertions.

[keithamus]

Hey @jwngr thanks for the issue!

#359 addressed a very similar bug, except it was with the array given as the expect param. It was quite a simple fix - in this case, we just need to change assertions.jsL1084 from actual.sort() to actual.slice(0).sort(). Of course then you'll also need to write some tests to back it up (you can copy the existing tests from #359 here and here and just tweak them to assert on the keys() param instead).

If you'd like to write up a PR for this, then please do so, and I'll happily merge it in. Doing so means you'll get on our hall of fame 😄

[jwngr]

It looks like this is actually just a dupe of #359. Upgrading to chai 2.x.x confirms as much. Glad it's already fixed!

Updating the line you suggested won't have any effect since actual is created from an Object.keys() call. So the sort() there isn't necessary.

Thanks for the quick turnaround!