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Many Lints

dispose_fields

v0.4.0WarningFixConfigurableResource Management

Flags instance fields in State subclasses whose type has a dispose(), close(), or cancel() method but the field is not cleaned up in the widget’s dispose() method. Common types include TextEditingController, FocusNode, AnimationController, StreamController, StreamSubscription, and Timer.

Why use this rule

Section titled “Why use this rule”

Disposable resources that are not cleaned up cause memory leaks. A TextEditingController that is never disposed keeps its listeners and internal state alive indefinitely. This rule checks that every field with a cleanup method has a matching call in dispose(), catching missing or incomplete cleanup.

See also: State.dispose() | Dart lint: cancel_subscriptions | Dart lint: close_sinks

Don’t

Section titled “Don’t”
class _BadState extends State<BadWidget> {
  final _textController = TextEditingController();
  final _focusNode = FocusNode();
  final _streamController = StreamController<int>();


  // No dispose() method -- all fields leak


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


class _IncompleteState extends State<IncompleteWidget> {
  final _controller1 = TextEditingController();
  final _controller2 = TextEditingController();


  @override
  void dispose() {
    _controller1.dispose();
    // _controller2 is missing!
    super.dispose();
  }


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

Do

Section titled “Do”
class _GoodState extends State<GoodWidget> {
  final _textController = TextEditingController();
  final _focusNode = FocusNode();


  @override
  void dispose() {
    _textController.dispose();
    _focusNode.dispose();
    super.dispose();
  }


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


class _StreamState extends State<StreamWidget> {
  final _streamController = StreamController<int>();


  @override
  void dispose() {
    _streamController.close();
    super.dispose();
  }


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

Turning this rule off

Section titled “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:
  dispose_fields: false

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

Options

Section titled “Options”
analysis_options.yaml
many_lints:
  rules:
    dispose_fields:
      additional_cleanup_methods: [release, shutdown]
Option Type Default Description
cleanup_methods list of strings [dispose, close, cancel] Replaces the cleanup method names the rule looks for
additional_cleanup_methods list of strings [] Extends whichever list applies
state_base_classes list of strings [] Extra base classes treated as state. Only needed for a base that does not extend Flutter’s State; an intermediate BaseState<T> is already recognised

Order matters: it is the priority used when a type declares more than one cleanup method. Names added via additional_cleanup_methods are appended, so a project’s own release() is only chosen when the type declares no standard cleanup method.

Both options apply to detection and recognition — a method listed here counts both as “this field needs cleaning up” and as “this call cleans it up”.

Section titled “Related rules”