currentDartFilePath function
Returns the path to the caller's .dart file.
If packageRelative is true, returns a path relative to the package root.
If packageRelative is false, returns an absolute path.
This does not work for Dart for the Web.
Note that Platform.script does not work for imported files and
consequently does not work with the Dart test runner.
Implementation
String currentDartFilePath({bool packageRelative = false}) {
var caller = stacktrace.Frame.caller(1);
return packageRelative ? caller.library : caller.uri.toFilePath();
}