throttleTime repeats the event if there was only one in the window #817

import 'dart:async';

import 'package:rxdart/rxdart.dart';

Future<void> main() async {
  final controller = StreamController();

  controller.stream
      .throttleTime(Duration(seconds: 1), leading: true, trailing: true)
      .listen((e) {
        print(e);
      });

  controller.add(1);

  await Future.delayed(Duration(seconds: 2));
}

Expected:

1

Actual:

1
1

The doc is wrong because it says "instead" and contradicts the first line:

But I don't see a reason for the documented behavior. By allowing both leading and trailing to be true, the interface is misleading. If trailing was meant to suppress the leading, it had to be an enum with leading and trailing as values.

leading must take priority and emit the first event right away. And then trailing should emit the last event only if something else came after that.

If this is not what this transformer is supposed to do, we need another one that actually does that because it's a common need.