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lint: StatefulWidget could be a StatelessWidget #3683

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goderbauer opened this issue Sep 13, 2022 · 4 comments · May be fixed by #3725
Open

lint: StatefulWidget could be a StatelessWidget #3683

goderbauer opened this issue Sep 13, 2022 · 4 comments · May be fixed by #3725
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lint-request status-accepted type-enhancement A request for a change that isn't a bug

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@goderbauer
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Occasionally, I see Flutter code where people use StatefulWidgets even though a StatelessWidget would have been sufficient. Example:

class MyWidget extends StatefulWidget {
  const MyWidget({super.key});

  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

The State class doesn't store any state in member variables and it also doesn't use any of the properties provided by Sate (e.g. mounted). This could easily be refactored to be a more concise StatelessWidget:

class MyWidget extends StatelessWidget {
  const MyWidget({super.key});

  @override
  Widget build(BuildContext context) {
    return Container();
  }
}

I wonder if it would be possible to have a lint for this?

Of course, from a functional perspective using a StatefulWidget here is totally fine, the additional performance overhead of a StatefulWidget over a StatelessWidget is probably neglectable. However, using a StatelessWidget where appropriate leads to more compact, concise, and readable code and is more idiomatic, IMO.
@bwilkerson
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I wonder if it would be possible to have a lint for this?

Yes, the lint appears to be well defined, so it should be possible to implement it. I'm not sure how often code like this is written, so it's hard to gauge how much value such a lint would bring to users, but it seems doable.

@elbeicktalat
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I'm not sure how often code like this is written
@bwilkerson I agree with about the complexity, but if we make the following simple checks than I think we are good to go.

  1. Check if widget hasn't a setState
  2. Check if the widget hasn't a life cycle methods
  3. Check if the widget hasn't any non final field (optional)

@a14n a14n linked a pull request Sep 23, 2022 that will close this issue
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@srawlins
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@pq as this rule is Flutter-specific, I'm not sure how many "yays" you want in order to declare it "accepted." FWIW there isn't any disagreement.

@pq
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pq commented Apr 17, 2023

Looks good to me. Thanks!

@srawlins srawlins added the type-enhancement A request for a change that isn't a bug label Mar 29, 2024
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Add unnecessary_stateful_widgets a14n/linter
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@pq @srawlins @goderbauer @bwilkerson @elbeicktalat