fix: correctly handle nullable types of collections (#786)

Author: incendial

CHANGELOG.md

@@ -8,6 +8,7 @@
 * fix: support index expressions for [`no-magic-number`](https://dartcodemetrics.dev/docs/rules/common/no-magic-number) rule.
 * fix: correctly split exclude path
 * chore: restrict `analyzer` version to `>=2.4.0 <3.5.0`.
+* fix: correctly handle nullable types of collections for [`avoid-collection-methods-with-unrelated-types`](https://dartcodemetrics.dev/docs/rules/common/avoid-collection-methods-with-unrelated-types)
 
 ## 4.13.0
 

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_collection_methods_with_unrelated_types/avoid_collection_methods_with_unrelated_types_rule.dart

@@ -3,6 +3,7 @@
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:collection/collection.dart';
 

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

@@ -64,7 +64,9 @@ class _Visitor extends RecursiveAstVisitor<void> {
   ) {
     if (parentElement != null &&
         childType != null &&
-        childType.asInstanceOf(parentElement.element) == null) {
+        childType.asInstanceOf(parentElement.element) == null &&
+        !(parentElement.type.nullabilitySuffix == NullabilitySuffix.question &&
+            childType.isDartCoreNull)) {
       _expressions.add(node);
     }
   }

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_collection_methods_with_unrelated_types/avoid_collection_methods_with_unrelated_types_rule_test.dart

@@ -6,6 +6,8 @@ import '../../../../../helpers/rule_test_helper.dart';
 
 const _examplePath =
     'avoid_collection_methods_with_unrelated_types/examples/example.dart';
+const _nullableExamplePath =
+    'avoid_collection_methods_with_unrelated_types/examples/nullable_example.dart';
 
 void main() {
   group('AvoidCollectionMethodsWithUnrelatedTypesRule', () {
@@ -132,5 +134,32 @@ void main() {
         ],
       );
     });
+
+    test('reports about found issues for nullable collections', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_nullableExamplePath);
+      final issues = AvoidCollectionMethodsWithUnrelatedTypesRule().check(unit);
+
+      RuleTestHelper.verifyIssues(
+        issues: issues,
+        startLines: [4, 10, 15, 20, 25, 30],
+        startColumns: [5, 5, 5, 5, 5, 5],
+        locationTexts: [
+          'regularMap[null]',
+          'nullableMap["str"]',
+          'regularList.remove(null)',
+          'nullableList.remove("str")',
+          'regularSet.contains(null)',
+          'nullableSet.contains("str")',
+        ],
+        messages: [
+          'Avoid collection methods with unrelated types.',
+          'Avoid collection methods with unrelated types.',
+          'Avoid collection methods with unrelated types.',
+          'Avoid collection methods with unrelated types.',
+          'Avoid collection methods with unrelated types.',
+          'Avoid collection methods with unrelated types.',
+        ],
+      );
+    });
   });
 }

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_collection_methods_with_unrelated_types/examples/nullable_example.dart

@@ -0,0 +1,32 @@
+void main() {
+  {
+    final regularMap = Map<int, String>();
+    regularMap[null] = "value"; // LINT
+
+    final nullableMap = Map<int?, String>();
+    nullableMap[42] = "value";
+    nullableMap[null] = "value";
+    final value = nullableMap[null];
+    nullableMap["str"] = "value"; // LINT
+  }
+
+  {
+    final regularList = [10, 20, 30];
+    regularList.remove(null); // LINT
+
+    final nullableList = <int?>[10, 20, 30, null];
+    nullableList.remove(null);
+    nullableList.remove(20);
+    nullableList.remove("str"); // LINT
+  }
+
+  {
+    final regularSet = {10, 20, 30};
+    regularSet.contains(null); // LINT
+
+    final nullableSet = {10, 20, 30, null};
+    nullableSet.contains(null);
+    nullableSet.contains(42);
+    nullableSet.contains("str"); // LINT
+  }
+}