Ensure options with value undefined are selected

[acelaya]

Fix an existing issue in MultiSelect, where options with value undefined, which special purpose is to clear the selection entirely, setting an empty array, are never marked as selected.

Additionally, when this type of option is selected, the listbox is automatically closed regardless of how it is selected (by clicking on it or by clicking on its checkbox). This is because this option will never be selectable together with other options, so it doesn't really make sense to keep it open.

Because of the point above, we should probably consider a different look-and-feel for this type of option, but I'm deferring that.

clear-option-fix-2024-08-21_11.54.59.mp4

[acelaya]

Using <Option value={undefined} /> is not entirely intuitive, so we may want to move to a more idiomatic approach with a more clear API.

This draft proposes an alternative approach to do that #1671, that we can merge later after the main issue is solved.

[acelaya]

Being more explicit on what is the "special" value.

[robertknight]

Can you add a test case for the new behavior. Otherwise this looks good.

[acelaya]

Can you add a test case for the new behavior.

Done

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (cb89a41) to head (0b32fde).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1672   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           61        61           
  Lines         1061      1067    +6     
  Branches       413       415    +2     
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+ Hits          1061      1067    +6     

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