always_remove_listener

v0.4.0WarningFixConfigurableResource Management

Flags addListener() calls in State lifecycle methods (initState, didUpdateWidget, didChangeDependencies) that do not have a matching removeListener() call in dispose(). Missing removal causes memory leaks when the Listenable outlives the widget.

Why use this rule

Every addListener() on a ChangeNotifier, ValueNotifier, or AnimationController creates a strong reference to the callback. If the listener is not removed in dispose(), the callback (and everything it captures) stays in memory even after the widget is unmounted. This rule ensures every add has a matching remove with the same target and callback.

See also: ChangeNotifier | removeListener | Dart lint: cancel_subscriptions

Don’t

class _BadState extends State<BadWidget> {
  final ValueNotifier<int> _counter = ValueNotifier(0);

  @override
  void initState() {
    super.initState();
    _counter.addListener(_onChanged); // No matching removeListener
  }

  void _onChanged() => setState(() {});

  @override
  Widget build(BuildContext context) => const SizedBox();
}

Do

class _GoodState extends State<GoodWidget> {
  final ValueNotifier<int> _counter = ValueNotifier(0);

  @override
  void initState() {
    super.initState();
    _counter.addListener(_onChanged);
  }

  @override
  void dispose() {
    _counter.removeListener(_onChanged);
    super.dispose();
  }

  void _onChanged() => setState(() {});

  @override
  Widget build(BuildContext context) => const SizedBox();
}

Turning this rule off

This rule is in the core preset, so it is on with preset: core, preset: recommended or preset: opinionated.

To turn it off:

many_lints.yaml

rules:
  always_remove_listener: false

To keep the rule on but skip certain paths, use per-rule exclude.

Options

Projects with a state abstraction that does not extend Flutter’s State can opt that base class into this rule:

analysis_options.yaml

analysis_options.yaml

many_lints:
  rules:
    always_remove_listener:
      state_base_classes: [AppState]

many_lints.yaml

many_lints.yaml

rules:
  always_remove_listener:
    state_base_classes: [AppState]

Option	Type	Default	Description
state_base_classes	list of strings	[]	Additional non-State base classes whose subclasses should be treated as state classes

Related rules

• avoid_unremovable_callbacks_in_listeners — Don’t pass an inline closure to addListener.
• dispose_fields — Ensure State fields with disposal methods are cleaned up in dispose().
• dispose_provided_instances — Ensure disposable instances in Riverpod providers are cleaned up with ref.onDispose.
• avoid_late_final_reassignment — Flag a late final field assigned twice on one path.