in lib/src/parser.dart [245:263]
bool _parseLongOption() {
// Hand coded regexp: r'^--([a-zA-Z\-_0-9]+)(=(.*))?$'
// Two hyphens then at least one letter/digit/hyphen, optionally an equal
// sign followed by zero or more anything-but-newlines.
if (!_current.startsWith('--')) return false;
var index = _current.indexOf('=');
var name =
index == -1 ? _current.substring(2) : _current.substring(2, index);
for (var i = 0; i != name.length; ++i) {
if (!_isLetterDigitHyphenOrUnderscore(name.codeUnitAt(i))) return false;
}
var value = index == -1 ? null : _current.substring(index + 1);
if (value != null && (value.contains('\n') || value.contains('\r'))) {
return false;
}
return _handleLongOption(name, value);
}