Add the bloc_related_class_naming lint (#504)

* Add the `bloc_related_class_naming` lint

* Add tests for classes in parts

* Update note

* Add a doc comment

* Simplify and allow configuring suffixes

* Don't pass entire config around

Author: PiotrRogulski

packages/leancode_lint/README.md

@@ -218,6 +218,59 @@ None.
 
 </details>
 
+<details>
+<summary>`bloc_related_class_naming`</summary>
+
+### `bloc_related_class_naming`
+
+**DO** follow the naming convention for Bloc/Cubit related classes.
+
+For `ExampleBloc`:
+- Event class: `ExampleEvent`
+- State class: `ExampleState`
+- Presentation Event class: `ExamplePresentationEvent`
+
+For `ExampleCubit`:
+- State class: `ExampleState`
+- Presentation Event class: `ExamplePresentationEvent`
+
+> [!NOTE]
+> This lint only checks classes defined in the same library (including parts) as the Bloc/Cubit.
+> Presentation events are only checked if the `bloc_presentation` package is used.
+
+**BAD:**
+
+```dart
+class MyBloc extends Bloc<WrongEvent, WrongState> {}
+```
+
+**GOOD:**
+
+```dart
+class MyBloc extends Bloc<MyEvent, MyState> {}
+```
+
+#### Configuration
+
+Configured via `LeanCodeLintConfig.blocRelatedClassNaming`:
+
+```dart
+import 'package:leancode_lint/plugin.dart';
+
+final plugin = LeanCodeLintPlugin(
+  name: 'my_lints',
+  config: LeanCodeLintConfig(
+    blocRelatedClassNaming: BlocRelatedClassNamingConfig(
+      stateSuffix: 'State',
+      eventSuffix: 'Event',
+      presentationEventSuffix: 'PresentationEvent',
+    ),
+  ),
+);
+```
+
+</details>
+
 <details>
 <summary><code>catch_parameter_names</code></summary>
 

packages/leancode_lint/lib/config.dart

@@ -3,6 +3,7 @@ final class LeanCodeLintConfig {
     this.applicationPrefix,
     this.designSystemItemReplacements = const {},
     this.catchParameterNames = const .new(),
+    this.blocRelatedClassNaming = const .new(),
   });
 
   /// Used by some rules (e.g. `prefix_widgets_returning_slivers`) to match
@@ -19,6 +20,30 @@ final class LeanCodeLintConfig {
 
   /// Configuration for the `catch_parameter_names` rule.
   final CatchParameterNamesConfig catchParameterNames;
+
+  /// Configuration for the `bloc_related_class_naming` rule.
+  final BlocRelatedClassNamingConfig blocRelatedClassNaming;
+}
+
+/// Configuration for the `bloc_related_class_naming` rule.
+///
+/// Each suffix is appended to the BLoC/Cubit subject name (the part before
+/// `Bloc` or `Cubit`) to form the expected class name.
+///
+/// For example, for `FooBloc` the default expected names are:
+/// - state → `FooState`
+/// - event → `FooEvent`
+/// - presentation event → `FooPresentationEvent`
+class BlocRelatedClassNamingConfig {
+  const BlocRelatedClassNamingConfig({
+    this.stateSuffix = 'State',
+    this.eventSuffix = 'Event',
+    this.presentationEventSuffix = 'PresentationEvent',
+  });
+
+  final String stateSuffix;
+  final String eventSuffix;
+  final String presentationEventSuffix;
 }
 
 class CatchParameterNamesConfig {

packages/leancode_lint/lib/plugin.dart

@@ -7,6 +7,7 @@ import 'package:leancode_lint/src/assists/convert_record_into_nominal_type.dart'
 import 'package:leancode_lint/src/lints/add_cubit_suffix_for_cubits.dart';
 import 'package:leancode_lint/src/lints/avoid_conditional_hooks.dart';
 import 'package:leancode_lint/src/lints/avoid_single_child_in_multi_child_widget.dart';
+import 'package:leancode_lint/src/lints/bloc_related_class_naming.dart';
 import 'package:leancode_lint/src/lints/catch_parameter_names.dart';
 import 'package:leancode_lint/src/lints/constructor_parameters_and_fields_should_have_the_same_order.dart';
 import 'package:leancode_lint/src/lints/hook_widget_does_not_use_hooks.dart';
@@ -40,13 +41,22 @@ final class LeanCodeLintPlugin extends Plugin {
     ).forEach(registry.registerWarningRule);
     registry
       ..registerWarningRule(StartCommentsWithSpace())
-      ..registerWarningRule(PrefixWidgetsReturningSlivers(config: config))
+      ..registerWarningRule(
+        PrefixWidgetsReturningSlivers(
+          applicationPrefix: config.applicationPrefix,
+        ),
+      )
       ..registerFixForRule(
         StartCommentsWithSpace.code,
         AddStartingSpaceToComment.new,
       )
       ..registerWarningRule(AddCubitSuffixForYourCubits())
-      ..registerWarningRule(CatchParameterNames(config: config))
+      ..registerWarningRule(
+        BlocRelatedClassNaming(config: config.blocRelatedClassNaming),
+      )
+      ..registerWarningRule(
+        CatchParameterNames(config: config.catchParameterNames),
+      )
       ..registerWarningRule(AvoidConditionalHooks())
       ..registerWarningRule(HookWidgetDoesNotUseHooks())
       ..registerFixForRule(

packages/leancode_lint/lib/src/bloc_utils.dart

@@ -0,0 +1,93 @@
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:leancode_lint/src/type_checker.dart';
+
+const blocChecker = TypeChecker.fromName('Bloc', packageName: 'bloc');
+
+const cubitChecker = TypeChecker.fromName('Cubit', packageName: 'bloc');
+
+const blocPresentationMixinChecker = TypeChecker.fromName(
+  'BlocPresentationMixin',
+  packageName: 'bloc_presentation',
+);
+
+String? getBlocSubject(String className, {required BlocType blocType}) =>
+    switch (blocType) {
+      .bloc when className.endsWith('Bloc') => className.substring(
+        0,
+        className.length - 4,
+      ),
+      .cubit when className.endsWith('Cubit') => className.substring(
+        0,
+        className.length - 5,
+      ),
+      _ => null,
+    };
+
+enum BlocType { bloc, cubit }
+
+BlocType? determineBlocType(Element? element) {
+  if (element == null) {
+    return null;
+  }
+
+  if (blocChecker.isAssignableFrom(element)) {
+    return .bloc;
+  } else if (cubitChecker.isAssignableFrom(element)) {
+    return .cubit;
+  }
+
+  return null;
+}
+
+class BlocInfo {
+  const BlocInfo({
+    required this.type,
+    this.stateType,
+    this.eventType,
+    this.presentationEventType,
+  });
+
+  final BlocType type;
+  final TypeAnnotation? stateType;
+  final TypeAnnotation? eventType;
+  final TypeAnnotation? presentationEventType;
+}
+
+BlocInfo? getBlocInfo(ClassDeclaration node) {
+  final extendsClause = node.extendsClause;
+  final superclass = extendsClause?.superclass;
+  final superclassElement = superclass?.element;
+
+  final type = determineBlocType(superclassElement);
+  if (type == null) {
+    return null;
+  }
+
+  final typeArguments = superclass?.typeArguments?.arguments;
+
+  final (eventType, stateType) = switch (typeArguments) {
+    [final state] when type == .cubit => (null, state),
+    [final event, final state] when type == .bloc => (event, state),
+    _ => (null, null),
+  };
+
+  TypeAnnotation? presentationEventType;
+  if (node.withClause case final withClause?) {
+    for (final mixin in withClause.mixinTypes) {
+      if (mixin.element case final mixinElement?
+          when blocPresentationMixinChecker.isExactly(mixinElement)) {
+        if (mixin.typeArguments?.arguments case [_, final presentationEvent]) {
+          presentationEventType = presentationEvent;
+        }
+      }
+    }
+  }
+
+  return .new(
+    type: type,
+    stateType: stateType,
+    eventType: eventType,
+    presentationEventType: presentationEventType,
+  );
+}

packages/leancode_lint/lib/src/lints/bloc_related_class_naming.dart

@@ -0,0 +1,106 @@
+import 'package:analyzer/analysis_rule/analysis_rule.dart';
+import 'package:analyzer/analysis_rule/rule_context.dart';
+import 'package:analyzer/analysis_rule/rule_visitor_registry.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:leancode_lint/config.dart';
+import 'package:leancode_lint/src/bloc_utils.dart';
+import 'package:leancode_lint/src/utils.dart';
+
+/// Enforces consistent naming of state, event, and presentation event classes
+/// related to a BLoC or Cubit.
+///
+/// Given a BLoC or Cubit named `FooBloc` or `FooCubit`, the associated classes
+/// should be named:
+/// - state → `FooState`
+/// - event → `FooEvent`
+/// - presentation event → `FooPresentationEvent`
+///
+/// The suffixes are configurable via [BlocRelatedClassNamingConfig].
+class BlocRelatedClassNaming extends AnalysisRule {
+  BlocRelatedClassNaming({this.config = const .new()})
+    : super(name: code.lowerCaseName, description: code.problemMessage);
+
+  final BlocRelatedClassNamingConfig config;
+
+  static const code = LintCode(
+    'bloc_related_class_naming',
+    "The name of {0}'s {1} should be {2}.",
+    severity: .WARNING,
+  );
+
+  @override
+  LintCode get diagnosticCode => code;
+
+  @override
+  void registerNodeProcessors(
+    RuleVisitorRegistry registry,
+    RuleContext context,
+  ) {
+    registry.addClassDeclaration(this, _Visitor(this, context, config));
+  }
+}
+
+class _Visitor extends SimpleAstVisitor<void> {
+  _Visitor(this.rule, this.context, this.config);
+
+  final AnalysisRule rule;
+  final RuleContext context;
+  final BlocRelatedClassNamingConfig config;
+
+  @override
+  void visitClassDeclaration(ClassDeclaration node) {
+    final blocInfo = getBlocInfo(node);
+    if (blocInfo == null) {
+      return;
+    }
+
+    final classElement = node.declaredFragment?.element;
+    final className = node.namePart.typeName.lexeme;
+    final subject = getBlocSubject(className, blocType: blocInfo.type);
+
+    if (subject == null) {
+      return;
+    }
+
+    void checkName(TypeAnnotation type, String classType, String suffix) {
+      final expectedName = '$subject$suffix';
+
+      if (type case NamedType(
+        :final name,
+        :final element?,
+        :final CompilationUnit root,
+      ) when name.lexeme != expectedName) {
+        if (element.library != classElement?.library) {
+          return;
+        }
+
+        final declaration = root.declarations
+            .whereType<ClassDeclaration>()
+            .firstWhereOrNull((d) => d.declaredFragment?.element == element);
+
+        rule.reportAtToken(
+          declaration?.namePart.typeName ?? name,
+          arguments: [className, classType, expectedName],
+        );
+      }
+    }
+
+    if (blocInfo.stateType case final stateType?) {
+      checkName(stateType, 'state', config.stateSuffix);
+    }
+
+    if (blocInfo.eventType case final eventType?) {
+      checkName(eventType, 'event', config.eventSuffix);
+    }
+
+    if (blocInfo.presentationEventType case final presentationEventType?) {
+      checkName(
+        presentationEventType,
+        'presentation event',
+        config.presentationEventSuffix,
+      );
+    }
+  }
+}

packages/leancode_lint/lib/src/lints/catch_parameter_names.dart

@@ -20,7 +20,7 @@ class CatchParameterNames extends AnalysisRule {
   CatchParameterNames({required this.config})
     : super(name: code.lowerCaseName, description: code.problemMessage);
 
-  final LeanCodeLintConfig config;
+  final CatchParameterNamesConfig config;
 
   static const code = LintCode(
     'catch_parameter_names',
@@ -46,7 +46,7 @@ class _Visitor extends SimpleAstVisitor<void> {
 
   final AnalysisRule rule;
   final RuleContext context;
-  final LeanCodeLintConfig config;
+  final CatchParameterNamesConfig config;
 
   @override
   void visitCatchClause(CatchClause node) {
@@ -81,8 +81,8 @@ enum _CatchClauseParameter {
   exception,
   stackTrace;
 
-  String preferredName(LeanCodeLintConfig config) => switch (this) {
-    exception => config.catchParameterNames.exception,
-    stackTrace => config.catchParameterNames.stackTrace,
+  String preferredName(CatchParameterNamesConfig config) => switch (this) {
+    exception => config.exception,
+    stackTrace => config.stackTrace,
   };
 }