logger.dart

library logger;

import 'verbose.dart';
import 'plain.dart';

log(message) {
  print(const String.fromEnvironment("logger.level"));
  if (const String.fromEnvironment("logger.level") == "verbose") {
    logVerbose(message);
  } else {
    logPlain(message);
  }
}

main.dart

import 'logger.dart';

main() {
  log("Hi");
}

plain.dart

logPlain(message) {
  print("Plain $message");
}

verbose.dart

logVerbose(message) {
  print("Verbose $message");
}