global.should = require("chai").should() doesn't work

[domenic]

Not sure why this is or what to do about it, so I wanted to record it so we can look into it later.

Basically, in my Mocha fixture I tried to do

global.should = require("chai").should();

But then when I tried to run

should.not.exist(undefined);

I got a big error saying that "{ ... all the properties of the global object ... } should not exist". So it seemed to be picking up Object.prototype.should instead of global.should, which was surprising.

This was under Node 0.8 with Chai 1.1.1, Mocha 1.3.0.

[logicalparadox]

I know exactly what is happening, and its a bit of a paradox..

Remember, should extends Object.prototype, and global falls into that category. Thus, even though you are assigning global.should the return value of chai.should(), its getting overwritten as the property should. I'm actually surprised this hasn't shown up as an issue before because it is the same reason you can't call chai.should() twice on the same export.. as chai.should() gets overwritten and then you can do chai.should.have.property('version'). This is why we have chai.Should() as an alias...

Use global.Should = require('chai').Should(). All your problems will go away.

[domenic]

Nice workaround, I should have thought of that. Let's say I was OCD though, and didn't like capitalizing non-constructor functions :P. Can we make this work?

After looking into it the problem is that Chai installs an empty setter on Object.prototype. This by itself is pretty bad; if you'd omitted the setter, we'd at least get an error (when in strict mode). So we should fix that at least.

One workaround is to redefine the property instead of set it. (In spec language, use [[DefineOwnProperty]] instead of [[Put]]). This avoids triggering the empty setter. And indeed it works:

require("chai").should();

Object.defineProperty(global, "should", {
    value: require("chai").Should(),
    enumerable: true,
    configurable: true,
    writable: true
});

should.not.exist(5); // => expected 5 to not exist

But what about a non-empty setter that does this for us? I.e.

Object.defineProperty(Object.prototype, "should", {
    set: function (value) {
        Object.defineProperty(this, "should", {
            value: value,
            enumerable: true,
            configurable: true,
            writable: true
        });
    },
    /* the rest as before */
});

Thoughts?

[logicalparadox]

If we can make it all work without breaking anything, I'm for it.

[domenic]

OK cool! I'll work on it this weekend.

[logicalparadox]

Any thoughts/progress on this?

[domenic]

Oh goodness, this got lost in the GitHub notifications clusterfuck :-/. Really just need an hour or two... hopefully soon, grr!

[logicalparadox]

If this continues to trouble you, can you open a new issue with the details?

[tonovotny]

Sorry for incomplete comments before (kids jumped on my keyboard...)

[nackjicholson]

Version 1.5.0

Mocha in the browser, with requirejs, and should. Based on this https://github.com/karlbright/requirejs-mocha-chai-bootstrap

I get a big global object that is not null. I can console out the variable I'm testing against, and it says it's null.