cancel_subscriptions

Cancel instances of dart:async StreamSubscription.

DO invoke cancel on instances of dart:async StreamSubscription.

Cancelling instances of StreamSubscription prevents memory leaks and unexpected behavior.

BAD:

class A {
  StreamSubscription _subscriptionA; // LINT
  void init(Stream stream) {
    _subscriptionA = stream.listen((_) {});
  }
}

BAD:

void someFunction() {
  StreamSubscription _subscriptionF; // LINT
}

GOOD:

class B {
  StreamSubscription _subscriptionB; // OK
  void init(Stream stream) {
    _subscriptionB = stream.listen((_) {});
  }
​
  void dispose(filename) {
    _subscriptionB.cancel();
  }
}

GOOD:

void someFunctionOK() {
  StreamSubscription _subscriptionB; // OK
  _subscriptionB.cancel();
}

Known limitations

This rule does not track all patterns of StreamSubscription instantiations and cancellations. See linter#317 for more information.

To enable the cancel_subscriptions rule, add cancel_subscriptions under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - cancel_subscriptions

If you're instead using the YAML map syntax to configure linter rules, add cancel_subscriptions: true under linter > rules:

linter:
  rules:
    cancel_subscriptions: true