feat: add rule for final_defined_class

examples/nilts_example/lib/main.dart

@@ -4,7 +4,7 @@ void main() {
   runApp(const MainApp());
 }
 
-class MainApp extends StatelessWidget {
+final class MainApp extends StatelessWidget {
   const MainApp({super.key});
 
   @override

packages/nilts/README.md

@@ -725,6 +725,36 @@ See also:
 
 </details>
 
+### final_defined_class
+
+<details>
+
+<!-- prettier-ignore-start -->
+- Target SDK     : >= Flutter 3.10.0 (Dart 3.0.0)
+- Rule type      : Practice
+- Maturity level : Experimental
+- Quick fix      : ✅
+<!-- prettier-ignore-end -->
+
+**Prefer** marking your class as final if it is not intended to be extended.
+
+**BAD:**
+<!-- prettier-ignore-start -->
+```dart
+class MyClass {}
+```
+<!-- prettier-ignore-end -->
+
+**GOOD:**
+
+<!-- prettier-ignore-start -->
+```dart
+final class MyClass {}
+```
+<!-- prettier-ignore-end -->
+
+</details>
+
 ## Assists
 
 Upcoming... 🚀

packages/nilts/lib/nilts.dart

@@ -5,6 +5,7 @@ import 'package:nilts/src/lints/defined_async_value_setter_type.dart';
 import 'package:nilts/src/lints/defined_value_callback_type.dart';
 import 'package:nilts/src/lints/defined_value_getter_type.dart';
 import 'package:nilts/src/lints/defined_void_callback_type.dart';
+import 'package:nilts/src/lints/final_defined_class.dart';
 import 'package:nilts/src/lints/fixed_text_scale_rich_text.dart';
 import 'package:nilts/src/lints/flaky_tests_with_set_up_all.dart';
 import 'package:nilts/src/lints/low_readability_numeric_literals.dart';
@@ -43,5 +44,7 @@ class _NiltsLint extends PluginBase {
         const ShrinkWrappedScrollView(),
         if (_dartVersion >= const DartVersion(major: 3, minor: 0, patch: 0))
           UnnecessaryRebuildsFromMediaQuery(_dartVersion),
+        if (_dartVersion >= const DartVersion(major: 3, minor: 0, patch: 0))
+          const FinalDefinedClass(),
       ];
 }

packages/nilts/lib/src/lints/defined_async_callback_type.dart

@@ -31,7 +31,7 @@ import 'package:nilts/src/change_priority.dart';
 /// See also:
 ///
 /// - [AsyncCallback typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/AsyncCallback.html)
-class DefinedAsyncCallbackType extends DartLintRule {
+final class DefinedAsyncCallbackType extends DartLintRule {
   /// Create a new instance of [DefinedAsyncCallbackType].
   const DefinedAsyncCallbackType() : super(code: _code);
 
@@ -76,7 +76,7 @@ class DefinedAsyncCallbackType extends DartLintRule {
       ];
 }
 
-class _ReplaceWithAsyncCallbackType extends DartFix {
+final class _ReplaceWithAsyncCallbackType extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/defined_async_value_getter_type.dart

@@ -32,7 +32,7 @@ import 'package:nilts/src/change_priority.dart';
 /// See also:
 ///
 /// - [AsyncValueGetter typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/AsyncValueGetter.html)
-class DefinedAsyncValueGetterType extends DartLintRule {
+final class DefinedAsyncValueGetterType extends DartLintRule {
   /// Create a new instance of [DefinedAsyncValueGetterType].
   const DefinedAsyncValueGetterType() : super(code: _code);
 
@@ -82,7 +82,7 @@ class DefinedAsyncValueGetterType extends DartLintRule {
       ];
 }
 
-class _ReplaceWithAsyncValueGetter extends DartFix {
+final class _ReplaceWithAsyncValueGetter extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/defined_async_value_setter_type.dart

@@ -32,7 +32,7 @@ import 'package:nilts/src/change_priority.dart';
 /// See also:
 ///
 /// - [AsyncValueSetter typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/AsyncValueSetter.html)
-class DefinedAsyncValueSetterType extends DartLintRule {
+final class DefinedAsyncValueSetterType extends DartLintRule {
   /// Create a new instance of [DefinedAsyncValueSetterType].
   const DefinedAsyncValueSetterType() : super(code: _code);
 
@@ -81,7 +81,7 @@ class DefinedAsyncValueSetterType extends DartLintRule {
       ];
 }
 
-class _ReplaceWithAsyncValueSetter extends DartFix {
+final class _ReplaceWithAsyncValueSetter extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/defined_value_callback_type.dart

@@ -34,7 +34,7 @@ import 'package:nilts/src/change_priority.dart';
 ///
 /// - [ValueChanged typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/ValueChanged.html)
 /// - [ValueSetter typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/ValueSetter.html)
-class DefinedValueChangedType extends _DefinedValueCallbackType {
+final class DefinedValueChangedType extends _DefinedValueCallbackType {
   /// Create a new instance of [DefinedValueChangedType].
   const DefinedValueChangedType() : super(_code);
 
@@ -77,7 +77,7 @@ class DefinedValueChangedType extends _DefinedValueCallbackType {
 ///
 ///   - [ValueSetter typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/ValueSetter.html)
 ///   - [ValueChanged typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/ValueChanged.html)
-class DefinedValueSetterType extends _DefinedValueCallbackType {
+final class DefinedValueSetterType extends _DefinedValueCallbackType {
   /// Create a new instance of [DefinedValueSetterType].
   const DefinedValueSetterType() : super(_code);
 
@@ -93,23 +93,23 @@ class DefinedValueSetterType extends _DefinedValueCallbackType {
       ];
 }
 
-class _ReplaceWithValueChanged extends _ReplaceWithValueCallbackType {
+final class _ReplaceWithValueChanged extends _ReplaceWithValueCallbackType {
   _ReplaceWithValueChanged()
       : super(
           'ValueChanged',
           ChangePriority.replaceWithValueChanged,
         );
 }
 
-class _ReplaceWithValueSetter extends _ReplaceWithValueCallbackType {
+final class _ReplaceWithValueSetter extends _ReplaceWithValueCallbackType {
   _ReplaceWithValueSetter()
       : super(
           'ValueSetter',
           ChangePriority.replaceWithValueSetter,
         );
 }
 
-class _DefinedValueCallbackType extends DartLintRule {
+final class _DefinedValueCallbackType extends DartLintRule {
   const _DefinedValueCallbackType(LintCode code)
       : _lintCode = code,
         super(code: code);
@@ -147,7 +147,7 @@ class _DefinedValueCallbackType extends DartLintRule {
   }
 }
 
-class _ReplaceWithValueCallbackType extends DartFix {
+final class _ReplaceWithValueCallbackType extends DartFix {
   _ReplaceWithValueCallbackType(
     this._typeName,
     this._changePriority,

packages/nilts/lib/src/lints/defined_value_getter_type.dart

@@ -32,7 +32,7 @@ import 'package:nilts/src/change_priority.dart';
 /// See also:
 ///
 /// - [ValueGetter typedef - foundation library - Dart API](https://api.flutter.dev/flutter/foundation/ValueGetter.html)
-class DefinedValueGetterType extends DartLintRule {
+final class DefinedValueGetterType extends DartLintRule {
   /// Create a new instance of [DefinedValueGetterType].
   const DefinedValueGetterType() : super(code: _code);
 
@@ -79,7 +79,7 @@ class DefinedValueGetterType extends DartLintRule {
       ];
 }
 
-class _ReplaceWithValueGetter extends DartFix {
+final class _ReplaceWithValueGetter extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/defined_void_callback_type.dart

@@ -31,7 +31,7 @@ import 'package:nilts/src/change_priority.dart';
 /// See also:
 ///
 /// - [VoidCallback typedef - dart:ui library - Dart API](https://api.flutter.dev/flutter/dart-ui/VoidCallback.html)
-class DefinedVoidCallbackType extends DartLintRule {
+final class DefinedVoidCallbackType extends DartLintRule {
   /// Create a new instance of [DefinedVoidCallbackType].
   const DefinedVoidCallbackType() : super(code: _code);
 
@@ -73,7 +73,7 @@ class DefinedVoidCallbackType extends DartLintRule {
       ];
 }
 
-class _ReplaceWithVoidCallbackType extends DartFix {
+final class _ReplaceWithVoidCallbackType extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/final_defined_class.dart

@@ -0,0 +1,90 @@
+import 'package:analyzer/error/error.dart' as analyzer;
+import 'package:analyzer/error/listener.dart';
+import 'package:custom_lint_builder/custom_lint_builder.dart';
+
+/// A class for `final_defined_class` rule.
+///
+/// This rule checks if the class is not intended to be extended.
+///
+/// - Target SDK     : >= Flutter 3.10.0 (Dart 3.0.0)
+/// - Rule type      : Practice
+/// - Maturity level : Experimental
+/// - Quick fix      : ✅
+///
+/// **Consider** add `final` keyword to the class declaration.
+///
+/// **BAD:**
+/// ```dart
+/// class MyClass {}
+/// ```
+///
+/// **GOOD:**
+/// ```dart
+/// final class MyClass {}
+/// ```
+final class FinalDefinedClass extends DartLintRule {
+  /// Create a new instance of [FinalDefinedClass].
+  const FinalDefinedClass() : super(code: _code);
+
+  static const _code = LintCode(
+    name: 'final_defined_class',
+    problemMessage: 'Please add the final keyword to the class declaration.',
+    correctionMessage: 'Try adding the final keyword to the class declaration.',
+    url: 'https://github.com/dassssshers/nilts#prefer_final_class',
+  );
+
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ErrorReporter reporter,
+    CustomLintContext context,
+  ) {
+    context.registry.addClassDeclaration((node) {
+      if (node.sealedKeyword != null ||
+          node.abstractKeyword != null ||
+          node.finalKeyword != null ||
+          node.baseKeyword != null ||
+          node.interfaceKeyword != null ||
+          node.mixinKeyword != null) {
+        return;
+      }
+
+      reporter.atToken(
+        node.name,
+        _code,
+      );
+    });
+  }
+
+  @override
+  List<Fix> getFixes() => [
+        _AddFinalKeyword(),
+      ];
+}
+
+final class _AddFinalKeyword extends DartFix {
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ChangeReporter reporter,
+    CustomLintContext context,
+    analyzer.AnalysisError analysisError,
+    List<analyzer.AnalysisError> others,
+  ) {
+    context.registry.addClassDeclaration((node) {
+      if (!node.sourceRange.intersects(analysisError.sourceRange)) return;
+
+      reporter
+          .createChangeBuilder(
+        message: 'Add final keyword',
+        priority: 100,
+      )
+          .addDartFileEdit((builder) {
+        builder.addSimpleInsertion(
+          node.classKeyword.offset,
+          'final ',
+        );
+      });
+    });
+  }
+}

packages/nilts/lib/src/lints/fixed_text_scale_rich_text.dart

@@ -64,7 +64,7 @@ import 'package:nilts_core/nilts_core.dart';
 ///
 /// - [Text.rich constructor - Text - widgets library - Dart API](https://api.flutter.dev/flutter/widgets/Text/Text.rich.html)
 /// - [RichText class - widgets library - Dart API](https://api.flutter.dev/flutter/widgets/RichText-class.html)
-class FixedTextScaleRichText extends DartLintRule {
+final class FixedTextScaleRichText extends DartLintRule {
   /// Create a new instance of [FixedTextScaleRichText].
   const FixedTextScaleRichText() : super(code: _code);
 
@@ -113,7 +113,7 @@ class FixedTextScaleRichText extends DartLintRule {
       ];
 }
 
-class _ReplaceWithTextRich extends DartFix {
+final class _ReplaceWithTextRich extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,
@@ -153,7 +153,7 @@ class _ReplaceWithTextRich extends DartFix {
   }
 }
 
-class _AddTextScaler extends DartFix {
+final class _AddTextScaler extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,
@@ -186,7 +186,7 @@ class _AddTextScaler extends DartFix {
 
 /// Legacy version of [FixedTextScaleRichText].
 /// This rule is for under Flutter 3.16.0.
-class FixedTextScaleRichTextLegacy extends DartLintRule {
+final class FixedTextScaleRichTextLegacy extends DartLintRule {
   /// Create a new instance of [FixedTextScaleRichTextLegacy].
   const FixedTextScaleRichTextLegacy() : super(code: _code);
 
@@ -233,7 +233,7 @@ class FixedTextScaleRichTextLegacy extends DartLintRule {
       ];
 }
 
-class _AddTextScaleFactor extends DartFix {
+final class _AddTextScaleFactor extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/flaky_tests_with_set_up_all.dart

@@ -52,7 +52,7 @@ import 'package:nilts_core/nilts_core.dart';
 ///
 /// - [setUpAll function - flutter_test library - Dart API](https://api.flutter.dev/flutter/flutter_test/setUpAll.html)
 /// - [setUp function - flutter_test library - Dart API](https://api.flutter.dev/flutter/flutter_test/setUp.html)
-class FlakyTestsWithSetUpAll extends DartLintRule {
+final class FlakyTestsWithSetUpAll extends DartLintRule {
   /// Create a new instance of [FlakyTestsWithSetUpAll].
   const FlakyTestsWithSetUpAll() : super(code: _code);
 
@@ -97,7 +97,7 @@ class FlakyTestsWithSetUpAll extends DartLintRule {
       ];
 }
 
-class _ReplaceWithSetUp extends DartFix {
+final class _ReplaceWithSetUp extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,
@@ -125,7 +125,7 @@ class _ReplaceWithSetUp extends DartFix {
   }
 }
 
-class _UnwrapSetUpAll extends DartFix {
+final class _UnwrapSetUpAll extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,

packages/nilts/lib/src/lints/low_readability_numeric_literals.dart

@@ -29,7 +29,7 @@ import 'package:nilts/src/change_priority.dart';
 ///
 /// - [Digit Separators in Dart 3.6](https://medium.com/dartlang/announcing-dart-3-6-778dd7a80983)
 /// - [Built-in types | Dart](https://dart.dev/language/built-in-types#numbers)
-class LowReadabilityNumericLiterals extends DartLintRule {
+final class LowReadabilityNumericLiterals extends DartLintRule {
   /// Creates a new instance of [LowReadabilityNumericLiterals].
   const LowReadabilityNumericLiterals() : super(code: _code);
 
@@ -67,7 +67,7 @@ class LowReadabilityNumericLiterals extends DartLintRule {
       ];
 }
 
-class _AddDigitSeparators extends DartFix {
+final class _AddDigitSeparators extends DartFix {
   @override
   void run(
     CustomLintResolver resolver,