Wrap non-chainable methods in proxies

[meeber]

Extends proxy protection to non-chainable methods (including overwritten non-chainable methods) with a helpful error message. Example:

expect(true).to.equal.true;  // Invalid Chai property: equal.true. See docs for proper usage of "equal".

[keithamus]

This error message is a bit unfriendly, I feel like it doesn't explicitly point out where the user went wrong. Could we instead have something like Invalid Chai property equal.pizza. Did you mean equal(pizza)?

[meeber]

@keithamus Agreed it can be better. I struggled with the phrasing quite a bit actually. The reason I ended up with the current phrasing is because many of the alternatives I explored only offer sensible advice part of the time.

For example:

expect(x).to.be.equal.to.true;
// Invalid Chai property: equal.to. Did you mean equal(to)?

expect(x).to.be.a.string.with.length(4);
// Invalid Chai property: string.with. Did you mean string(with)?

expect(x).to.throw.an.error;
// Invalid Chai property: throw.an. Did you mean throw(an)?

expect(x).to.be.within.2.and.4;
// Invalid Chai property: within.2. Did you mean within(2)?

I feel uncomfortable with Chai reacting to the user's mistake by suggesting an alternative that's also incorrect, especially in the last case since it demonstrates using within with only one argument when it actually requires two.

Could do something like: Invalid Chai property: equal.pizza. See docs for proper usage of the "equal" assertion.

Or the high-effort solution with customized messages for each method: Invalid usage of .within. Correct usage: .within(start, finish).

[keithamus]

Okay, I like the idea of "See docs...". I agree that we dont want to present wrong info, but I also what to give users a chance to fix without immediately resorting to a support channel (like our issue tracker 😵)

[meeber]

This one is ready for review. But first, a special shout out to:

• @vieiralucas for making these changes possible via Return new assertion with flags copied over instead of this. Fix #791 #799.
• @lucasfcosta for not recruiting any additional lucases, thus allowing the Chai team to maintain a balanced lucas-to-non-lucas ratio, thereby ensuring that the world doesn't plunge into chaos.
• @keithamus for being a moose, and a fine one at that.

[keithamus]

Okay, this LGTM. Great work @meeber 👍 🎉

[vieiralucas]

Awesome work, LGTM

ps: I like pizza to 🍕

[vieiralucas]

LGTM

github review system pls