[prosemirror-autocomplete] add cancelOnSpace option

[benrbray]

Thanks very much for the prosemirror-autocomplete package, it's great!

cancelOnFirstSpace

What's the intended behavior of cancelOnFirstSpace? The docs say:

cancelOnFirstSpace?: boolean, cancels the auto complete on first space, default is true

This could be interpreted in two different ways:

1. the autocomplete will be cancelled the first time the user types a space (that is, no spaces are allowed whatsoever)
2. the autocomplete will be cancelled if the first character typed after the autocomplete trigger is a space, but after that, spaces are allowed

My desired behavior is the first one -- no spaces allowed, but the code behaves according to the second interpretation:

editor/packages/prosemirror-autocomplete/src/decoration.ts

Lines 143 to 153 in 8f576d7

	const checkCancelOnSpace = type?.cancelOnFirstSpace ?? true;
	if (
	checkCancelOnSpace &&
	filter.length === 0 &&
	(event.key === ' ' || event.key === 'Spacebar')
	) {
	closeAutocomplete(view);
	// Take over the space creation so no other input rules are fired
	view.dispatch(view.state.tr.insertText(' ').scrollIntoView());
	return true;
	}

Proposal

I propose the following, which I've implemented in this PR.

• add a new option cancelOnSpace, which cancels autocompletion whenever space is pressed
• if cancelOnSpace = true, the value of cancelOnFirstSpace is ignored
• if cancelOnSpace = false, the behavior of cancelOnFirstSpace is the same as before

I also added some comments and updated the readme to document this change.

(Optional) Rename cancelOnFirstSpace?

Optionally, I suggest renaming cancelOnFirstSpace to cancelOnInitialSpace, but I understand if you prefer to keep it the same to avoid a breaking change.

Conclusion

Happy to make any changes to the PR based on your feedback. Thanks!