Listeners are not removed when provider refreshes

[Colton127]

Describe the bug
Riverpod documentation states:

Listeners will automatically be removed when the provider rebuilds (such as when a provider listened with [watch] changes).

However, listeners remain alive and even continuously rebuild (without removing prior instances) using the code below.

To Reproduce

import 'dart:async';
import 'package:flutter_riverpod/flutter_riverpod.dart';

final printCountNotifierProvider = NotifierProvider<PrintCountNotifier, bool>(PrintCountNotifier.new);

class PrintCountNotifier extends Notifier<bool> {
  bool _printCount = false;

  @override
  bool build() {
    if (!_printCount) return false;
    ref.listen(countNotifierProvider, (previous, next) {
      print('PrintCount: $_printCount | Count: $next');
    });
    return true;
  }

  void toggle() {
    _printCount = !_printCount;
    state = build();
  }
}

final countNotifierProvider = NotifierProvider<CountNotifier, int>(CountNotifier.new);

class CountNotifier extends Notifier<int> {
  @override
  int build() {
    Timer.periodic(const Duration(seconds: 1), (timer) {
      state = state + 1;
    });
    return 0;
  }
}

Expected behavior
Expected: countNotifierProvider listener should be automatically removed when printCountNotifierProvider rebuilds.

Actual output:

PrintCount: true | Count: 1
PrintCount: true | Count: 2
PrintCount: true | Count: 3
PrintCount: true | Count: 4
PrintCount: true | Count: 5
PrintCount: true | Count: 6
PrintCount: true | Count: 7
PrintCount: true | Count: 8
PrintCount: true | Count: 9
PrintCount: false | Count: 10
PrintCount: false | Count: 11
PrintCount: false | Count: 12
PrintCount: false | Count: 13
PrintCount: false | Count: 14
PrintCount: false | Count: 15
PrintCount: false | Count: 16
PrintCount: false | Count: 17
PrintCount: false | Count: 18
PrintCount: false | Count: 19
PrintCount: false | Count: 20
PrintCount: false | Count: 21
PrintCount: false | Count: 22
PrintCount: false | Count: 23
PrintCount: false | Count: 24
PrintCount: false | Count: 25
PrintCount: false | Count: 26
PrintCount: false | Count: 27
PrintCount: false | Count: 28
PrintCount: false | Count: 29
PrintCount: false | Count: 30
PrintCount: false | Count: 31
PrintCount: true | Count: 32
PrintCount: true | Count: 32
PrintCount: true | Count: 33
PrintCount: true | Count: 33
PrintCount: true | Count: 34
PrintCount: true | Count: 34
PrintCount: true | Count: 35
PrintCount: true | Count: 35

Notice how each number is printed twice at the end. The previous listener is never removed, even though a new one is created.

[rrousselGit]

state = build();

That's not legal. Only Riverpod should call build.
Your provider didn't really rebuild.

If you want a provider to rebuild itself, use ref.invalidateSelf(). Then Riverpod will reinvoke build, and listeners will be updated accordingly