Can I get a "stack trace" that traces all async calls, with Dart?

5
votes

Consider code like this:

import 'dart:async';

foo() {
  new Timer(onesec, bar);
}

bar() {
  throw "from bar";
}

const onesec = const Duration(seconds:1);

main() {
  runZoned(() {
  new Timer(onesec, foo);
  },
  onError: (e, stackTrace) => print(stackTrace));
}

How can I tell that bar was "called" by foo in the stackTrace that I print out?

I'd like to see something like:

bar
...
foo
...
main
1
dartdart-async

1 Answers

6
votes

Have a look at the stack_trace package. It uses zones to keep track of asynchronous callbacks. Capturing stack traces for every asynchronous callback is expensive, but for debugging it is definitely worth it.

Example output from the package:

http://dartlang.org/foo/bar.dart 10:11  Foo.<fn>.bar
http://dartlang.org/foo/baz.dart        Foo.<fn>.bar
===== asynchronous gap ===========================
http://dartlang.org/foo/bang.dart 10:11  Foo.<fn>.bar
http://dartlang.org/foo/quux.dart        Foo.<fn>.bar

According to the doc, the easiest way to get these traces is to use Chain.capture.