feat: ignore tear-off methods for avoid-unused-parameters (#1126)

Author: incendial

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* feat: ignore tear-off methods for [`avoid-unused-parameters`](https://dartcodemetrics.dev/docs/rules/common/avoid-unused-parameters).
 * feat: show warning for rules without config that require config to work.
 * fix: correctly handle FunctionExpressions for [`avoid-redundant-async`](https://dartcodemetrics.dev/docs/rules/common/avoid-redundant-async).
 * feat: support ignoring nesting for [`prefer-conditional-expressions`](https://dartcodemetrics.dev/docs/rules/common/prefer-conditional-expressions).

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_redundant_async/visitor.dart

@@ -9,12 +9,7 @@ class _Visitor extends RecursiveAstVisitor<void> {
   void visitMethodDeclaration(MethodDeclaration node) {
     super.visitMethodDeclaration(node);
 
-    final isOverride = node.metadata.any(
-      (node) =>
-          node.name.name == 'override' && node.atSign.type == TokenType.AT,
-    );
-
-    if (!isOverride && _hasRedundantAsync(node.body)) {
+    if (!isOverride(node.metadata) && _hasRedundantAsync(node.body)) {
       _nodes.add(node);
     }
   }

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/avoid_unused_parameters_rule.dart

@@ -1,7 +1,6 @@
 // ignore_for_file: public_member_api_docs
 
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/visitor.dart

@@ -19,12 +19,9 @@ class _Visitor extends RecursiveAstVisitor<void> {
       return;
     }
 
-    final isOverride = node.metadata.any(
-      (node) =>
-          node.name.name == 'override' && node.atSign.type == TokenType.AT,
-    );
+    final isTearOff = _usedAsTearOff(node);
 
-    if (!isOverride) {
+    if (!isOverride(node.metadata) && !isTearOff) {
       _unusedParameters.addAll(
         _getUnusedParameters(
           node.body,
@@ -77,6 +74,18 @@ class _Visitor extends RecursiveAstVisitor<void> {
   bool _hasNoUnderscoresInName(FormalParameter parameter) =>
       parameter.name != null &&
       parameter.name!.lexeme.replaceAll('_', '').isNotEmpty;
+
+  bool _usedAsTearOff(MethodDeclaration node) {
+    final name = node.name.lexeme;
+    if (!Identifier.isPrivateName(name)) {
+      return false;
+    }
+
+    final visitor = _InvocationsVisitor(name);
+    node.root.visitChildren(visitor);
+
+    return visitor.hasTearOffInvocations;
+  }
 }
 
 class _IdentifiersVisitor extends RecursiveAstVisitor<void> {
@@ -92,3 +101,22 @@ class _IdentifiersVisitor extends RecursiveAstVisitor<void> {
     }
   }
 }
+
+class _InvocationsVisitor extends RecursiveAstVisitor<void> {
+  final String methodName;
+
+  bool hasTearOffInvocations = false;
+
+  _InvocationsVisitor(this.methodName);
+
+  @override
+  void visitSimpleIdentifier(SimpleIdentifier node) {
+    if (node.name == methodName &&
+        node.staticElement is MethodElement &&
+        node.parent! is MethodInvocation) {
+      hasTearOffInvocations = true;
+    }
+
+    super.visitSimpleIdentifier(node);
+  }
+}

lib/src/utils/node_utils.dart

@@ -1,5 +1,6 @@
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/syntactic_entity.dart';
+import 'package:analyzer/dart/ast/token.dart';
 import 'package:source_span/source_span.dart';
 
 import '../analyzers/lint_analyzer/models/internal_resolved_unit_result.dart';
@@ -37,6 +38,11 @@ SourceSpan nodeLocation({
   );
 }
 
+bool isOverride(List<Annotation> metadata) => metadata.any(
+      (node) =>
+          node.name.name == 'override' && node.atSign.type == TokenType.AT,
+    );
+
 bool isEntrypoint(String name, NodeList<Annotation> metadata) =>
     name == 'main' ||
     _hasPragmaAnnotation(metadata) ||

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/avoid_unused_parameters_rule_test.dart

@@ -8,6 +8,8 @@ const _correctExamplePath =
     'avoid_unused_parameters/examples/correct_example.dart';
 const _incorrectExamplePath =
     'avoid_unused_parameters/examples/incorrect_example.dart';
+const _tearOffExamplePath =
+    'avoid_unused_parameters/examples/tear_off_example.dart';
 
 void main() {
   group('AvoidUnusedParametersRule', () {
@@ -61,5 +63,26 @@ void main() {
         ],
       );
     });
+
+    test('should report about found issues for tear-offs', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_tearOffExamplePath);
+      final issues = AvoidUnusedParametersRule().check(unit);
+
+      RuleTestHelper.verifyIssues(
+        issues: issues,
+        startLines: [8, 13, 13],
+        startColumns: [36, 23, 43],
+        locationTexts: [
+          'int value',
+          'String firstString',
+          'String secondString',
+        ],
+        messages: [
+          'Parameter is unused.',
+          'Parameter is unused.',
+          'Parameter is unused.',
+        ],
+      );
+    });
   });
 }

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unused_parameters/examples/tear_off_example.dart

@@ -0,0 +1,20 @@
+class TestClass {
+  String value;
+
+  void _someMethod(Function(String, int) callback) {
+    callback();
+  }
+
+  void _otherMethod(String string, int value) {
+    print(string);
+  }
+
+  // LINT
+  void _anotherMethod(String firstString, String secondString) {
+    someMethod(_otherMethod);
+    _someOtherMethod(value);
+  }
+
+  // LINT
+  _someOtherMethod(String value) {}
+}