avoid_unremovable_callbacks_in_listeners

v1.0.0WarningConfigurableResource Management

This rule flags a closure literal passed to addListener. removeListener matches by identity, and a closure creates a new object each time it is evaluated — so the listener can never be removed.

Why use this rule

removeListener(theClosure) compares object identity. A closure literal written at the call site is a different object from any closure you could later pass, so the removal silently does nothing and the listener stays registered.

Two consequences follow. The listener holds its captured scope — usually the whole State — alive for as long as the notifier lives, which is a genuine leak. And it keeps firing after disposal, so a setState inside it runs against a disposed element.

This pairs with always_remove_listener: that rule checks that a removal exists, this one checks that the removal can actually work.

Don’t

controller.addListener(() => setState(() {}));   // can never be removed

Do

Give the callback a stable identity:

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

@override
void initState() {
  super.initState();
  controller.addListener(_onChange);
}

@override
void dispose() {
  controller.removeListener(_onChange);
  super.dispose();
}

Known limitations

Only addListener and addStatusListener are recognised by default; a project wrapper can be added with additional_methods.

A registration with more than one argument is skipped, since this rule is about the add/remove pair specifically.

Turning this rule off

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

To turn it off:

rules:
  avoid_unremovable_callbacks_in_listeners: false

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

many_lints:
  rules:
    avoid_unremovable_callbacks_in_listeners:
      additional_methods: [addObserver]

rules:
  avoid_unremovable_callbacks_in_listeners:
    additional_methods: [addObserver]

Option	Type	Default	Description
`additional_methods`	list of strings	`[]`	Extra registration methods whose counterpart removes by identity

always_remove_listener — Ensure every addListener() has a matching removeListener() in dispose().
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.