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Many Lints

avoid_empty_setstate

v0.8.0WarningConfigurableState Management

This rule flags setState(() {}) — a call whose callback contains no statements.

Why use this rule

Section titled “Why use this rule”

An empty callback means the state was already mutated somewhere else and setState is being used purely as a “please rebuild” signal. It works, but it separates the mutation from the rebuild request, which causes three problems:

  • Readers cannot see what changed by looking at the setState call.
  • The framework’s debug assertions, which run around the callback, no longer bracket the actual mutation.
  • If the mutation later moves after the setState call, the rebuild silently renders stale values.

Putting the mutation inside the callback fixes all three and costs nothing.

See also: State.setState docs

Don’t

Section titled “Don’t”
class Counter extends StatefulWidget {
  const Counter({super.key});


  @override
  State<Counter> createState() => _CounterState();
}


class _CounterState extends State<Counter> {
  int _count = 0;


  void _increment() {
    _count++;
    // The rebuild request is detached from the change
    setState(() {});
  }


  @override
  Widget build(BuildContext context) => Text('$_count');
}

Do

Section titled “Do”
class Counter extends StatefulWidget {
  const Counter({super.key});


  @override
  State<Counter> createState() => _CounterState();
}


class _CounterState extends State<Counter> {
  int _count = 0;


  void _increment() {
    setState(() {
      _count++;
    });
  }


  @override
  Widget build(BuildContext context) => Text('$_count');
}

Known limitations

Section titled “Known limitations”

Only a genuinely empty block is reported. A callback containing any statement is left alone, even if that statement has no effect — proving a statement is a no-op is outside this rule’s scope.

Only an inline callback is inspected. setState(_noop) passes a method reference, and the rule does not follow it.

Turning this rule off

Section titled “Turning this rule off”

This rule is in the opinionated preset, so it is on with preset: opinionated, or by name:

many_lints.yaml
rules:
  avoid_empty_setstate: true

To turn it off again:

many_lints.yaml
rules:
  avoid_empty_setstate: false

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

Options

Section titled “Options”

Projects with a state abstraction that does not extend Flutter’s State can opt that base class into this rule:

analysis_options.yaml
many_lints:
  rules:
    avoid_empty_setstate:
      state_base_classes: [AppState]
Option Type Default Description
state_base_classes list of strings [] Additional non-State base classes whose subclasses should be treated as state classes
Section titled “Related rules”