feat: defined_void_callback_type (#39)

* feat: defined_void_callback_type

* docs: add docs for defined_void_callback_type

* test: add not lint test patterns

* docs: fix target sdk

packages/nilts/README.md

@@ -79,12 +79,35 @@ Some of lint rules support quick fixes on IDE.
 
 | Rule name | Overview | Target SDK | Rule type | Maturity level | Quick fix |
 | :-- | :-- | :--: | :--: | :--: | :--: |
+| [defined\_void\_callback\_type](#defined_void_callback_type) | Checks `void Function()` definitions. | Any versions nilts supports | Practice | Experimental | ✅️ |
 | [fixed\_text\_scale\_factor\_rich\_text](#fixed_text_scale_factor_rich_text) | Checks usage of `textScaleFactor` in `RichText` constructor. | Any versions nilts supports | Practice | Experimental | ✅️ |
 | [flaky\_tests\_with\_set\_up\_all](#flaky_tests_with_set_up_all) | Checks `setUpAll` usages. | Any versions nilts supports | Practice | Experimental | ✅️ |
 | [unnecessary\_rebuilds\_from\_media\_query](#unnecessary_rebuilds_from_media_query) | Checks `MediaQuery.xxxOf(context)` or `MediaQuery.maybeXxxOf(context)` usages. | >= Flutter 3.10.0 (Dart 3.0.0) | Practice | Experimental | ✅️ |
 
 ### Details
 
+#### defined_void_callback_type
+
+- Target SDK: Any versions nilts supports
+- Rule type: Practice
+- Maturity level: Experimental
+- Quick fix: ✅
+
+**Consider** replace `void Function()` with `VoidCallback` which is defined in Flutter SDK.
+
+**BAD:**
+
+```dart
+final void Function() callback;
+```
+
+
+**GOOD:**
+
+```dart
+final VoidCallback callback;
+```
+
 #### fixed_text_scale_factor_rich_text
 
 - Target SDK: Any versions nilts supports

packages/nilts/lib/nilts.dart

@@ -1,4 +1,5 @@
 import 'package:custom_lint_builder/custom_lint_builder.dart';
+import 'package:nilts/src/lints/defined_void_callback_type.dart';
 import 'package:nilts/src/lints/fixed_text_scale_factor_rich_text.dart';
 import 'package:nilts/src/lints/flaky_tests_with_set_up_all.dart';
 import 'package:nilts/src/lints/unnecessary_rebuilds_from_media_query.dart';
@@ -11,6 +12,7 @@ PluginBase createPlugin() => _NiltsLint();
 class _NiltsLint extends PluginBase {
   @override
   List<LintRule> getLintRules(CustomLintConfigs configs) => [
+        const DefinedVoidCallbackType(),
         const FixedTextScaleFactorRichText(),
         const FlakyTestsWithSetUpAll(),
         const UnnecessaryRebuildsFromMediaQuery(),

packages/nilts/lib/src/change_priority.dart

@@ -11,6 +11,9 @@ class ChangePriority {
   /// The priority for [_ReplaceWithSetUp].
   static const int replaceWithSetUp = 100;
 
+  /// The priority for [_ReplaceWithVoidCallback].
+  static const int replaceWithVoidCallback = 100;
+
   /// The priority for [_UnwrapSetUpAll].
   static const int unwrapSetUpAll = 90;
 }

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

@@ -0,0 +1,92 @@
+import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:analyzer/error/listener.dart';
+import 'package:custom_lint_builder/custom_lint_builder.dart';
+import 'package:nilts/src/change_priority.dart';
+
+/// A class for `defined_void_callback_type` rule.
+///
+/// This rule checks defining `void Function()` type.
+///
+/// - Target SDK: Any versions nilts supports
+/// - Rule type: Practice
+/// - Maturity level: Experimental
+/// - Quick fix: ✅
+///
+/// **Consider** replace `void Function()` with `VoidCallback` which is defined
+/// in Flutter SDK.
+///
+/// **BAD:**
+/// ```dart
+/// final void Function() callback;
+/// ```
+///
+/// **GOOD:**
+/// ```dart
+/// final VoidCallback callback;
+/// ```
+class DefinedVoidCallbackType extends DartLintRule {
+  /// Create a new instance of [DefinedVoidCallbackType].
+  const DefinedVoidCallbackType() : super(code: _code);
+
+  static const _code = LintCode(
+    name: 'defined_void_callback_type',
+    problemMessage: 'VoidCallback type is defined in Flutter SDK.',
+    url: 'https://github.com/ronnnnn/nilts#defined_void_callback_type',
+  );
+
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ErrorReporter reporter,
+    CustomLintContext context,
+  ) {
+    context.registry.addTypeAnnotation((node) {
+      final type = node.type;
+      // Do nothing if the type is not Function.
+      if (type is! FunctionType) return;
+
+      // Do nothing if Function has parameters.
+      if (type.parameters.isNotEmpty) return;
+
+      // Do nothing if the return type is not void.
+      final returnType = type.returnType;
+      if (returnType is! VoidType) return;
+
+      reporter.reportErrorForNode(_code, node);
+    });
+  }
+
+  @override
+  List<Fix> getFixes() => [
+        _ReplaceWithVoidCallbackType(),
+      ];
+}
+
+class _ReplaceWithVoidCallbackType extends DartFix {
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ChangeReporter reporter,
+    CustomLintContext context,
+    AnalysisError analysisError,
+    List<AnalysisError> others,
+  ) {
+    context.registry.addTypeAnnotation((node) {
+      if (!node.sourceRange.intersects(analysisError.sourceRange)) return;
+
+      reporter
+          .createChangeBuilder(
+        message: 'Replace with VoidCallback',
+        priority: ChangePriority.replaceWithVoidCallback,
+      )
+          .addDartFileEdit((builder) {
+        final delta = node.question != null ? -1 : 0;
+        builder.addSimpleReplacement(
+          node.sourceRange.getMoveEnd(delta),
+          'VoidCallback',
+        );
+      });
+    });
+  }
+}

packages/nilts_test/test/lints/defined_void_callback_type.dart

@@ -0,0 +1,79 @@
+// ignore_for_file: prefer_function_declarations_over_variables
+// ignore_for_file: type_init_formals
+// ignore_for_file: unused_element
+
+import 'package:flutter/material.dart';
+
+void main() {
+  runApp(const MainApp());
+}
+
+class MainApp extends StatelessWidget {
+  const MainApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp(
+      home: Scaffold(
+        body: Center(
+          child: MainButton(() {}),
+        ),
+      ),
+    );
+  }
+}
+
+class MainButton extends StatelessWidget {
+  const MainButton(
+    // expect_lint: defined_void_callback_type
+    void Function() this.onPressed, {
+    // expect_lint: defined_void_callback_type
+    void Function()? this.onNullablePressed,
+    void Function(int)? this.onParamPressed,
+    int Function()? this.onNotVoidPressed,
+    super.key,
+  });
+
+  // expect_lint: defined_void_callback_type
+  final void Function() onPressed;
+  // expect_lint: defined_void_callback_type
+  final void Function()? onNullablePressed;
+  final void Function(int)? onParamPressed;
+  final int Function()? onNotVoidPressed;
+
+  void _onPressed(
+    // expect_lint: defined_void_callback_type
+    void Function() onPressed, {
+    // expect_lint: defined_void_callback_type
+    void Function()? onNullablePressed,
+    void Function(int)? onParamPressed,
+    int Function()? onNotVoidPressed,
+  }) {}
+
+  @override
+  Widget build(BuildContext context) {
+    return FilledButton(
+      onPressed: () {
+        _onPressed(() {});
+        onPressed();
+      },
+      child: const Text('Hello World!'),
+    );
+  }
+}
+
+// expect_lint: defined_void_callback_type
+final void Function() globalFunction = () {};
+// expect_lint: defined_void_callback_type
+const void Function()? globalNullableFunction = null;
+const void Function(int)? globalParamFunction = null;
+const int Function()? globalNotVoidFunction = null;
+
+void _globalFunction(
+  // expect_lint: defined_void_callback_type
+  void Function() onPressed, {
+  // expect_lint: defined_void_callback_type
+  void Function()? onNullablePressed,
+  void Function(int)? onParamPressed,
+  int Function()? onNotVoidPressed,
+}) {}