validName function
Converts lower case names with underscore to UpperCamelCase (for classes) or lowerCamelCase (for class fields).
Implementation
String validName(String input, { bool firstCapital = false }) {
RegExp re = firstCapital ? RegExp(r'^[a-z]|[^a-zA-Z][a-z]') : RegExp(r'[^a-zA-Z\?][a-z]');
String result = input.replaceAllMapped(re, (Match match) => match.group(0)!.toUpperCase());
re = RegExp(r'^\??\d+|[^a-zA-Z0-9]');
result = result.replaceAll(re, '');
return result;
}