[WIP] Add selected to choice

[DanielVartanov]

Describe the change

Add selected property to Choice

Why are we doing this?

In PR #141 Piotr suggested

Alternatively, we could extend the Choice with a new state like selected. This would have an added benefit that you could define your choice as selected before the menu is rendered. Then we could remove the @selected collection and replace the call with an already sorted list:
choices.select(&:selected?)

Benefits

It also allows to pre-select default options by passing selected: true option to menu.choice

Drawbacks

• Breaks a promise of immutability of instances of Choice as described in public API
• A mixup/confusion between different ways of setting defaults
• It's still WIP, many edgecases (especially related to disabled options) must be re-analysed.

Requirements

Put an X between brackets on each line if you have done the item:
[X] Tests written & passing locally?
[X] Code style checked?
[X] Rebased with master branch?
[X] Documentation updated?

[DanielVartanov]

@piotrmurach just a note: It seems that an immutable entity which describes the choice (name, value, disabled etc) and a mutable entity which describes a presence of a choice in a collection (selected, maybe index etc) are separate entities, though I didn't find a good name for the latter yet they probably need to be separated.

[coveralls]

Coverage increased (+0.01%) to 97.355% when pulling 10d88f7 on DanielVartanov:add-selected-to-choice into b330a32 on piotrmurach:master.

[DanielVartanov]

Apologies for the failed test, something must've been wrong while rebasing, I'll double chek

[DanielVartanov]

Yes, default help has been changed recent, therefore the test has failed after rebasing. Fixed it now.

[piotrmurach]

Again I'm reluctant to lose the 'immutability' guarantee for the Choice class. There are few ideas anyhow that I'd like to port over to the gem whether or not we go with this solution.

[piotrmurach]

Same observation here, I do like the 'immutability' guarantee here. This is especially important when you may want to call the prompt recursively and 'loop' the choice selection.

[piotrmurach]

This is a good addition regardless.

[DanielVartanov]

Great, will cherry-pick this chunk too 👍

[DanielVartanov]

Done in #144