Build failing due to change in error comparison algo

[meeber]

Looks like #57 broke the build for IE 9 & 11 as well as Safari 10.

Apparently IE 9 & 11 add an enumerable description property to Error objects but not to TypeError objects, causing one of the comparison tests to fail. The description property appears to have the same value as message. (If message and description is empty, then IE 9 & 11 also add an enumerable number property, but that doesn't come into play with any of the tests.)

Apparently Safari 10 adds enumerable line, column, and sourceURL properties to all Error objects. This causes all of the tests to fail that expected two Error objects to be equal, since the line and/or column properties will always be different between Error objects.

What a pain. I'm not sure what the right solution is here.

[keithamus]

I think providing a custom comparator for Error objects that just checks name, message and perahps while we're at it some node-specific ones like code?

We can just add another case statement to http://github.com/chaijs/deep-eql/blob/62e2d5142921ec2b053b3c681487d99f227df02f/index.js#L197-L238

case 'Error':
  return keysEqual(leftHandOperand, rightHandOperand, ['name', 'message', 'code'], options)

[meeber]

Fair suggestion, and that's more or less what lodash and Node are doing, but without checking code. Will sleep on it.