repl: beep and ignore unrecognized inputs rather then crashing

[srp]

Fixes #9696

[ivarne]

Pretty useless to beep when beep is disabled.

[ivarne]

But that seems to be fixed in #9710

[Keno]

This isn't the right place to put this, because it's generic code. It should probably go in one of the keymaps instead.

[JeffBezanson]

Shouldn't the fallback behavior for unhandled keys apply to all keymaps?

[Keno]

This code isn't julia REPL specific. I would rather disallow creating keymaps that don't specify a default.

[stevengj]

@Keno, since this is the default that nearly all imaginable keymaps would want for undefined inputs, wouldn't it make more sense to put it here rather than force this code to be repeated in every keymap? If the keymap really wants to throw an exception, they can always specify a different default, no?

[srp]

I didn't understand what @Keno was saying at first, but I've been learning a lot more about keymaps. Now that I have a much better understanding about what's going on, I don't think we should be seeing this failure, I believe there may be a but where the default key in the keymap of the highest precedence isn't propagated to the lower precedent keymaps. I arrived at that this morning, but haven't had time to try to prove it and identify the bug.

If that's the case, I'd also agree with @Keno that this check should be replaced with an error at keymap creation time for any keymaps missing defaults.

[Keno]

I can take another look at the code. I suspect this place to add the default may be wrong anyway.