lt, lte, gt & gte no more work with strings or mongodb ObjectIds

In previous versions of chaiJS expect(x).to.be.lt(y) used to work with x and y being strings or mongodb ids.

Since recently, this comparison raises AssertionError: expected 'x' to be a number or a date .

This is a serious limitation, especially when checking the sort order of data arrays returned by RESTful APIs.

[meeber]

I’m definitely in favor of allowing strings as long as the target and given value are both strings.

The mongo objectids part is a bit tougher. I assume they’re objects that get coerced to strings during comparison via .valueOf?

[meeber]

In general I’m opposed to type coercion in an assertion library. However, in this particular case I think the normal risks associated with type coercion are mitigated.

The main mitigation is that both the target and the given value must both be strings; the same coercion happens to both values using the same string-to-number algorithm. This eliminates the element of surprise that is usually associated with problems that arise from type coercion. To me, the fact that strings are being converted to unicode code points in the background isn’t significantly different than dates being converted to milliseconds since the Unix epoch. I’m having trouble thinking of what exactly we’re protecting the user against by disallowing string-to-string comparisons.

I am, however, opposed to object-to-object comparisons; the coercion algorithm in that case isn’t consistent, and a lot of surprising things could happen.