assert.deepEqual hangs when comparing arrays if the array prototype was modified by Opal

[s-leroux]

Opal is a Ruby to JS converter. opal-runtime by @Mogztter is a helper library providing the runtime environment to run Ruby->JS converted programs.

Apparently, it modifies the prototype of the standard objects in such a way assert.deepEqual hangs (presumably on a circular reference):

> require('opal-runtime')
> assert = require('chai').assert
> assert.deepEqual([1,2,3], [1,2]);
## Hang here

I assume other libraries modifying the standard object's prototype in a similar way could cause Chai to hang too.

Tested with node v8.9.4, opal-runtime 1.0.1 and chai 4.1.2

[demurgos]

Maybe related to chaijs/deep-eql#51. (Edit: Probably not, see below)

A fix would be to use Function#apply instead of the methods on the objects.

[s-leroux]

Maybe @demurgos. Maybe not.

I tried to follow the code with the debugger. It does not seem to be stuck in an infinite loop. But I also noticed Chai found 850 visible properties on arrays and 800 on functions. So the issue might "just" be caused by a combinatorial explosion.

[s-leroux]

Related to #1109

[keithamus]

Hey @s-leroux thanks for the issue.

I'm sure this is actually a duplicate of #1109. assert.deepEqual works with circular references, so it is likely that the issue is with loupe, as mentioned in #1109. I'll close this one, but thanks for filing this issue and please don't hesitate to open any new ones if you find anything new!