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avoid-undisposed-instances

added in: 1.13.0
warning
Pro+
preset: recommended

Warns when an instance that has a dispose method is not assigned to a variable.

Not disposing such instances may lead to memory leaks and should be avoided.

⚙️ Config​

Set ignored-instances (default is empty) to ignore instances that are intended to be undisposed (example).

Set ignored-invocations (default is empty) to ignore specific invocation (example).

analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-undisposed-instances:
        ignored-instances:
          - SomeClass
        ignored-invocations:
          - WithAutoDispose

Example​

❌ Bad:

TextSpan(
  ...
  recognizer: LongPressGestureRecognizer() // LINT: This instance is not disposed. Try assigning it to a field and calling 'dispose'.
    ..onLongPress = _handlePress,
),

✅ Good:

class _SomeState extends State<Some> {
  late LongPressGestureRecognizer _longPressRecognizer;

  @override
  void initState() {
    super.initState();

    _longPressRecognizer = LongPressGestureRecognizer()
      ..onLongPress = _handlePress;
  }

  @override
  void dispose() {
    _longPressRecognizer.dispose(); // Correct, disposed

    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    ...
    TextSpan(
      ...
      recognizer: _longPressRecognizer,
    ),
    ...
  }
}

Example with "ignored-instances"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-undisposed-instances:
        ignored-instances:
          - LongPressGestureRecognizer

✅ Good:

TextSpan(
  ...
  recognizer: LongPressGestureRecognizer() // Correct, ignored
    ..onLongPress = _handlePress,
),

Example with "ignored-invocations"​

Config
analysis_options.yaml
dart_code_metrics:
  rules:
    - avoid-undisposed-instances:
        ignored-invocations:
          - WithAutoDispose

✅ Good:

// Correct, ignored
WithAutoDispose(
  ...
  recognizer: LongPressGestureRecognizer()
    ..onLongPress = _handlePress,
),