fix: ‘Number of Parameters’ skip copyWith methods. (#489)

Author: dkrutskikh

CHANGELOG.md

@@ -6,9 +6,10 @@
 * feat: add static code diagnostic `prefer-const-border-radius`.
 * feat: improve static code diagnostic `prefer-extracting-callbacks`: don't trigger on empty function blocks and ignore Flutter builder functions.
 * feat: improve unused files check, add support for `vm:entry-point` annotation.
-* fix: compute NumberOfParametersMetric only for functions and methods.
-* fix: skip synthetic tokens while compute 'Source lines of Code'.
-* fix: update 'Maintainability Index' metric comment message.
+* fix: compute `Number of Parameters` only for functions and methods.
+* fix: `Number of Parameters` skip copyWith methods.
+* fix: skip synthetic tokens while compute `Source lines of Code`.
+* fix: update `Maintainability Index` metric comment message.
 
 ## 4.3.3
 

lib/src/analyzers/lint_analyzer/metrics/metrics_list/number_of_parameters_metric.dart

@@ -1,4 +1,5 @@
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:collection/collection.dart';
 
 import '../../models/entity_type.dart';
 import '../../models/internal_resolved_unit_result.dart';
@@ -40,8 +41,23 @@ class NumberOfParametersMetric extends FunctionMetric<int> {
     Iterable<ScopedFunctionDeclaration> functionDeclarations,
     InternalResolvedUnitResult source,
     Iterable<MetricValue<num>> otherMetricsValues,
-  ) =>
-      node is FunctionDeclaration || node is MethodDeclaration;
+  ) {
+    if (node is FunctionDeclaration) {
+      return true;
+    } else if (node is MethodDeclaration) {
+      final className = functionDeclarations
+          .firstWhereOrNull((declaration) => declaration.declaration == node)
+          ?.enclosingDeclaration
+          ?.name;
+
+      return node.name.name != 'copyWith' ||
+          className == null ||
+          className !=
+              node.returnType?.type?.getDisplayString(withNullability: true);
+    }
+
+    return false;
+  }
 
   @override
   MetricComputationResult<int> computeImplementation(

test/analyzers/lint_analyzer/metrics/metrics_list/number_of_parameters_metric_test.dart

@@ -131,7 +131,17 @@ Future<void> main() async {
     });
 
     test('supports returns only for functions and methods', () {
-      const supports = [true, true, true, true, false, true, true];
+      const supports = [
+        true,
+        true,
+        true,
+        true,
+        false,
+        true,
+        true,
+        false,
+        false,
+      ];
 
       assert(
         scopeVisitor.functions.length == supports.length,

test/resources/number_of_parameters_metric_example.dart

@@ -45,3 +45,27 @@ class NumberOfParametersMetric extends FunctionMetric<int> {
     return MetricComputationResult(value: parametersCount ?? 0);
   }
 }
+
+class Foo {
+  final String a;
+  final String b;
+  final String c;
+  final String d;
+  final String e;
+
+  const Foo({
+    required this.a,
+    required this.b,
+    required this.c,
+    required this.d,
+    required this.e,
+  });
+
+  Foo copyWith({String a, String b, String c, String d, String e}) => Foo(
+        a: a ?? this.a,
+        b: b ?? this.b,
+        c: c ?? this.c,
+        d: d ?? this.d,
+        e: e ?? this.e,
+      );
+}