How to exclude debug code


Let’s say I have simple logger:

void main() {
  var logger = new MyLogger();
  logger.log("hello Dart");

I want this code to run in the dev mode (VM checked mode) but i don’t want it in my production code. And i want it to be “tree shaked” away with the dart2js compiler. Is there some standard way?


You could embed the code in an assert. Assertions are ignored in production code and I’m sure not built to JS when pub build is run in release mode.

class X {
  X() {
    print('x created');

  void log(String m) {

bool log(String m) {
  new X()..log(m);
      return true;

void main() {
  assert(() {
    new X()..log('in Assert');
    return true;

  assert(() => log('in Assert')); // use a wrapper function

When you create a wrapper method that returns true than you don’t have to do it explicit each time.

You can also take a look at this question How to achieve precompiler directive like functionality

Answered By – Günter Zöchbauer

Answer Checked By – Willingham (FlutterFixes Volunteer)

Leave a Reply

Your email address will not be published. Required fields are marked *