Accessibility: Screen Reader for single option p-selectButton reads incorrectly

[djpmsft]

I'm submitting a ... (check one with "x")

[x] bug report => Search github for a similar issue or PR before submitting
[ ] feature request => Please check if request is not on the roadmap already https://github.com/primefaces/primeng/wiki/Roadmap
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Current behavior

When using a screen reader to navigate through a set of selectButton options with multiple set as false, the narrator reads each value as 'unchecked checkbox'. When a user clicks space, the narrator will read 'checked checkbox'. If a user clicks space again, the narrator value goes back to 'unchecked checkbox' despite the value still being selected.

Expected behavior

If the multiple field is set to false, pressing the space bar should not affect the narration, especially if there is no visual/functional change. I also believe that labeling this component as a checkbox can be confusing to a user.

Minimal reproduction of the problem with instructions

This change is visible in the primeng documentation examples (https://primefaces.org/primeng/#/selectbutton).

1. In Edge, turn on the screen reader, and navigate to the 'Single' example
2. Go to the Visa option and press space
3. Press space again

You will see that despite Visa still being select, the narrator will read 'unchecked checkbox'

What is the motivation / use case for changing the behavior?

A user relying on the screen reader for navigation will not be able to interact with this control properly

Please tell us about your environment:

Windows 10, Node

• Angular version: 5.1.3

• PrimeNG version: 5.2.7

• Browser: [Edge ]

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version =