catch-or-return options to report `then(a, b)` or `then(null, b)`

[Jessidhia]

makePromise().then(thenHandler, catchHandler) is incorrectly considered correct by the always-catch plugin when allowThen: true is specified.

While the catchHandler will handle a rejection of the Promise returned by makePromise(), it will not handle any rejection that happens in the thenHandler; it needs to be handled by its own catch handler, which could be a .then(null /* | undefined */, catchHandler) according to allowThen: true.

[xjamundx]

I believe that the current behavior is correct as some people would rather do without catch or a second then altogether.

I see your point that they are going to be missing any crashes in the initial handler. I'd consider an allowThenStrict or something 🤔

What do you think?

[okcoker]

I'd consider an allowThenStrict or something

Would this disallow the second argument being used within .then() altogether? I'm all for having that as I don't think that's currently possible right?

[brettz9]

I think we may need allowThenStrict (to err on then(a, b) but pass for then(null, b)) and preventThenRejectHandler (which errs on both forms) as separate options.

[brettz9]

Maybe it is better for at least the latter option to be its own rule (and as might be tracked by #217).