dispose_provided_instances

v0.4.0 Warning Bloc / Riverpod

This rule flags instances created inside Riverpod provider callbacks or Notifier build() methods that have a dispose(), close(), or cancel() method but are not cleaned up via ref.onDispose(). It recognizes tear-off, lambda, and block body cleanup patterns.

Why use this rule

When a provider creates a disposable resource (like a controller, stream subscription, or service with a close() method) without registering cleanup, the resource leaks when the provider is destroyed. This leads to memory leaks and resource exhaustion over time. The ref.onDispose() callback ensures proper cleanup regardless of how or when the provider is disposed.

See also: Riverpod ref.onDispose

Don’t

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

class DisposableService {
  void dispose() {}
  String get value => 'hello';
}

// Instance has dispose() but ref.onDispose is not called
final badProvider = Provider<DisposableService>((ref) {
  final instance = DisposableService();
  return instance;
});

// Notifier build() creates disposable without ref.onDispose
class BadNotifier extends Notifier<DisposableService> {
  @override
  DisposableService build() {
    final instance = DisposableService();
    return instance;
  }
}

Do

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

class DisposableService {
  void dispose() {}
  String get value => 'hello';
}

// Using ref.onDispose with tear-off
final goodProvider = Provider<DisposableService>((ref) {
  final instance = DisposableService();
  ref.onDispose(instance.dispose);
  return instance;
});

// Using ref.onDispose with lambda
final goodLambdaProvider = Provider<DisposableService>((ref) {
  final instance = DisposableService();
  ref.onDispose(() => instance.dispose());
  return instance;
});

// Notifier build() with ref.onDispose
class GoodNotifier extends Notifier<DisposableService> {
  @override
  DisposableService build() {
    final instance = DisposableService();
    ref.onDispose(instance.dispose);
    return instance;
  }
}

Configuration

To disable this rule:

plugins:
  many_lints:
    diagnostics:
      dispose_provided_instances: false