Flag constructor
Implementation
Flag({this.short, this.long, required this.description})
: assert(
short != null || long != null,
'Either short or long should be not null',
),
assert(
short == null || (short.startsWith('-') && short.length == 2),
"Short should have format '-x', where x is a single symbol",
),
assert(
long == null || (long.startsWith('--') && long.length > 2),
"Long should have format '--xxx', where xxx is a long name of the flag",
);