AvoidUnnecessarySetStateRule class

Warns when setState is called directly in a lifecycle method.

Since: v0.1.4 | Updated: v4.13.0 | Rule version: v6

In initState/didChangeDependencies, state assignments take effect before the first build, so wrapping them in setState is unnecessary and misleading. However, setState inside closures (stream listeners, Future callbacks) is fine — those execute after the lifecycle method returns.

Example

BAD:

@override
void initState() {
  super.initState();
  setState(() { _value = 42; }); // unnecessary — assign directly
}

GOOD:

@override
void initState() {
  super.initState();
  _value = 42; // direct assignment before first build
  _sub = stream.listen((_) {
    if (mounted) setState(() {}); // deferred — runs after build
  });
}