No check for mandatory when using `option`

[ookami-kb]

When using argResults['foo'] there's a check for mandatory option:

if (option.mandatory && !_parsed.containsKey(name)) {
  throw ArgumentError('Option $name is mandatory.');
}

But the new strictly typed argResults.option('foo') doesn't have this check.

[christerswahn]

👍

[TheMaverickProgrammer]

Same problem. This is wildly unintuitive and unexpected. A simple check for mandatory inputs during parse() would be ideal too.