The main difference is about "What's a negatable option?"

(1) A single option with two behaviors (yes/no)
(2) Two different options (yes, no) but defined as a single one for convenience

Incase (1), we need a tri-state to differentiate these cases:

$useAnsi =$input->getOption('ansi');if (true ===$useAnsi) {// force ANSI usage}elseif (false ===$useAnsi) {// don't use ANSI}elseif (null ===$useAnsi) {// user didn't pass any ANSI preference;// we must decide what to do}

Incase (2), you only need two cases (the third one happens automatically):

$useAnsi =$input->getOption('ansi');$dontUseAnsi =$input->getOption('no-ansi');if ($useAnsi) {// force ANSI usage}elseif ($dontUseAnsi) {// don't use ANSI}else {// user didn't pass any ANSI preference;// we must decide what to do}

The BC break has been solved by setting the default tofalse for OUR--ansi option.
In that way:

• usinggetOption('ansi') will still return false
• people can useInputOption::VALUE_NEGATABLE with a defaultnull value and leverage the 3 states of the option.

Thank you@jderusse.