Fix # and * Behaviour

[jpoon]

Properly fixes #569.

Behaviour of # and * is expected to be:

1. If cursor selects whitespace, the word closest to right is chosen
2. If there is no word to the right of the cursor, a VIM error is thrown
3. Otherwise, searches for currently selected word.

[johnfn]

I'm beginning to think we should move away from throw and try/catch. The more I use them the more I feel like they're just a goto statement to some arbitrary point in the codebase.

I'd much rather prefer making the return type something like string | undefined to indicate failure and then handling that at the call site. Fortunately this change is pretty easy here.

[jpoon]

I prefer throw as it's a bit more declarative of what's going on; undefined is well, undefined and can be overloaded on what the caller should do with it. It doesn't matter in this case as the caller ignores the error, but eventually it would be nice to show this error on the status bar like how vim does it.

Did I sway you?

[johnfn]

I see what you're saying, but hailing from other languages with optionals, IMO returning an empty optional is as declarative as throwing an error. I like it because now the return value indicates "this function can fail" and the caller is forced to deal with it, or else get type errors.

As it is, anyone else who calls this function will have to remember that it throws or else they'll get into trouble.

I could see putting the status message on VimState actually. This seems nice to me because then we'd retain the behavior of updateView taking a VimState and rendering it to screen.

What do you think?

[jpoon]

As it is, anyone else who calls this function will have to remember that it throws or else they'll get into trouble.

Fair point. Coming from c#, the compiler would complain if you didn't properly catch an exception.