feat: add avoid-top-level-members-in-tests (#920)

Co-authored-by: Dmitry Krutskikh <dmitry.krutskikh@gmail.com>

Author: incendial

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 * feat: add static code diagnostic [`avoid-duplicate-exports`](https://dartcodemetrics.dev/docs/rules/common/avoid-duplicate-exports).
+* feat: add static code diagnostic [`avoid-top-level-members-in-tests`](https://dartcodemetrics.dev/docs/rules/common/avoid-top-level-members-in-tests).
 * feat: add static code diagnostic [`prefer-enums-by-name`](https://dartcodemetrics.dev/docs/rules/common/prefer-enums-by-name).
 
 ## 4.17.0-dev.1

lib/src/analyzers/lint_analyzer/rules/rules_factory.dart

@@ -16,6 +16,7 @@ import 'rules_list/avoid_non_null_assertion/avoid_non_null_assertion_rule.dart';
 import 'rules_list/avoid_preserve_whitespace_false/avoid_preserve_whitespace_false_rule.dart';
 import 'rules_list/avoid_returning_widgets/avoid_returning_widgets_rule.dart';
 import 'rules_list/avoid_throw_in_catch_block/avoid_throw_in_catch_block_rule.dart';
+import 'rules_list/avoid_top_level_members_in_tests/avoid_top_level_members_in_tests_rule.dart';
 import 'rules_list/avoid_unnecessary_setstate/avoid_unnecessary_setstate_rule.dart';
 import 'rules_list/avoid_unnecessary_type_assertions/avoid_unnecessary_type_assertions_rule.dart';
 import 'rules_list/avoid_unnecessary_type_casts/avoid_unnecessary_type_casts_rule.dart';
@@ -76,6 +77,7 @@ final _implementedRules = <String, Rule Function(Map<String, Object>)>{
   AvoidPreserveWhitespaceFalseRule.ruleId: AvoidPreserveWhitespaceFalseRule.new,
   AvoidReturningWidgetsRule.ruleId: AvoidReturningWidgetsRule.new,
   AvoidThrowInCatchBlockRule.ruleId: AvoidThrowInCatchBlockRule.new,
+  AvoidTopLevelMembersInTestsRule.ruleId: AvoidTopLevelMembersInTestsRule.new,
   AvoidUnnecessarySetStateRule.ruleId: AvoidUnnecessarySetStateRule.new,
   AvoidUnnecessaryTypeAssertionsRule.ruleId:
       AvoidUnnecessaryTypeAssertionsRule.new,

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_top_level_members_in_tests/avoid_top_level_members_in_tests_rule.dart

@@ -0,0 +1,45 @@
+// ignore_for_file: public_member_api_docs
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+
+import '../../../../../utils/node_utils.dart';
+import '../../../lint_utils.dart';
+import '../../../models/internal_resolved_unit_result.dart';
+import '../../../models/issue.dart';
+import '../../../models/severity.dart';
+import '../../models/common_rule.dart';
+import '../../rule_utils.dart';
+
+part 'visitor.dart';
+
+class AvoidTopLevelMembersInTestsRule extends CommonRule {
+  static const String ruleId = 'avoid-top-level-members-in-tests';
+
+  static const _warning = 'Avoid declaring top-level members in tests.';
+
+  AvoidTopLevelMembersInTestsRule([Map<String, Object> config = const {}])
+      : super(
+          id: ruleId,
+          severity: readSeverity(config, Severity.warning),
+          excludes: ['!test/**'],
+        );
+
+  @override
+  Iterable<Issue> check(InternalResolvedUnitResult source) {
+    final visitor = _Visitor();
+
+    source.unit.visitChildren(visitor);
+
+    return visitor.declarations
+        .map((declaration) => createIssue(
+              rule: this,
+              location: nodeLocation(
+                node: declaration,
+                source: source,
+              ),
+              message: _warning,
+            ))
+        .toList(growable: false);
+  }
+}

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

@@ -0,0 +1,65 @@
+part of 'avoid_top_level_members_in_tests_rule.dart';
+
+class _Visitor extends GeneralizingAstVisitor<void> {
+  final _declarations = <AstNode>[];
+
+  Iterable<AstNode> get declarations => _declarations;
+
+  @override
+  void visitClassDeclaration(ClassDeclaration node) {
+    if (!Identifier.isPrivateName(node.name.name)) {
+      _declarations.add(node);
+    }
+  }
+
+  @override
+  void visitMixinDeclaration(MixinDeclaration node) {
+    if (!Identifier.isPrivateName(node.name.name)) {
+      _declarations.add(node);
+    }
+  }
+
+  @override
+  void visitExtensionDeclaration(ExtensionDeclaration node) {
+    final name = node.name?.name;
+    if (name != null && !Identifier.isPrivateName(name)) {
+      _declarations.add(node);
+    }
+  }
+
+  @override
+  void visitEnumDeclaration(EnumDeclaration node) {
+    if (!Identifier.isPrivateName(node.name.name)) {
+      _declarations.add(node);
+    }
+  }
+
+  @override
+  void visitTypeAlias(TypeAlias node) {
+    if (!Identifier.isPrivateName(node.name.name)) {
+      _declarations.add(node);
+    }
+  }
+
+  @override
+  void visitFunctionDeclaration(FunctionDeclaration node) {
+    final name = node.name.name;
+    if (isEntrypoint(name, node.metadata)) {
+      return;
+    }
+
+    if (!Identifier.isPrivateName(name)) {
+      _declarations.add(node);
+    }
+  }
+
+  @override
+  void visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
+    final variables = node.variables.variables;
+
+    if (variables.isNotEmpty &&
+        !Identifier.isPrivateName(variables.first.name.name)) {
+      _declarations.add(variables.first);
+    }
+  }
+}

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_top_level_members_in_tests/avoid_top_level_members_in_tests_rule_test.dart

@@ -0,0 +1,51 @@
+import 'package:dart_code_metrics/src/analyzers/lint_analyzer/models/severity.dart';
+import 'package:dart_code_metrics/src/analyzers/lint_analyzer/rules/rules_list/avoid_top_level_members_in_tests/avoid_top_level_members_in_tests_rule.dart';
+import 'package:test/test.dart';
+
+import '../../../../../helpers/rule_test_helper.dart';
+
+const _examplePath = 'avoid_top_level_members_in_tests/examples/example.dart';
+
+void main() {
+  group('AvoidTopLevelMembersInTestsRule', () {
+    test('initialization', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_examplePath);
+      final issues = AvoidTopLevelMembersInTestsRule().check(unit);
+
+      RuleTestHelper.verifyInitialization(
+        issues: issues,
+        ruleId: 'avoid-top-level-members-in-tests',
+        severity: Severity.warning,
+      );
+    });
+
+    test('reports about found issues', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_examplePath);
+      final issues = AvoidTopLevelMembersInTestsRule().check(unit);
+
+      RuleTestHelper.verifyIssues(
+        issues: issues,
+        startLines: [1, 6, 10, 14, 18, 22, 26],
+        startColumns: [7, 1, 1, 1, 1, 1, 1],
+        locationTexts: [
+          'public = 1',
+          'void function() {}',
+          'class Class {}',
+          'mixin Mixin {}',
+          'extension Extension on String {}',
+          'enum Enum { first, second }',
+          'typedef Public = String;',
+        ],
+        messages: [
+          'Avoid declaring top-level members in tests.',
+          'Avoid declaring top-level members in tests.',
+          'Avoid declaring top-level members in tests.',
+          'Avoid declaring top-level members in tests.',
+          'Avoid declaring top-level members in tests.',
+          'Avoid declaring top-level members in tests.',
+          'Avoid declaring top-level members in tests.',
+        ],
+      );
+    });
+  });
+}

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_top_level_members_in_tests/examples/example.dart

@@ -0,0 +1,28 @@
+final public = 1; // LINT
+final _private = 2;
+
+void main() {}
+
+void function() {} // LINT
+
+void _function() {}
+
+class Class {} // LINT
+
+class _Class {}
+
+mixin Mixin {} // LINT
+
+mixin _Mixin {}
+
+extension Extension on String {} // LINT
+
+extension _Extension on String {}
+
+enum Enum { first, second } // LINT
+
+enum _Enum { first, second }
+
+typedef Public = String; // LINT
+
+typedef _Private = String;

website/docs/rules/common/avoid-top-level-members-in-tests.md

@@ -0,0 +1,53 @@
+# Avoid top-level members in tests
+
+## Rule id {#rule-id}
+
+avoid-top-level-members-in-tests
+
+## Severity {#severity}
+
+Warning
+
+## Description {#description}
+
+Warns when a public top-level member (expect the entrypoint) is declared inside a test file.
+
+It helps reduce code bloat and find unused declarations in test files.
+
+### Example {#example}
+
+Bad:
+
+```dart
+final public = 1; // LINT
+
+void function() {} // LINT
+
+class Class {} // LINT
+
+mixin Mixin {} // LINT
+
+extension Extension on String {} // LINT
+
+enum Enum { first, second } // LINT
+
+typedef Public = String; // LINT
+```
+
+Good:
+
+```dart
+final _private = 2;
+
+void _function() {}
+
+class _Class {}
+
+mixin _Mixin {}
+
+extension _Extension on String {}
+
+enum _Enum { first, second }
+
+typedef _Private = String;
+```

website/docs/rules/overview.md

@@ -59,6 +59,10 @@ Rules configuration is [described here](../getting-started/configuration#configu
 
     Warns when call `throw` in a catch block.
 
+- [avoid-top-level-members-in-tests](./common/avoid-top-level-members-in-tests.md)
+
+    Warns when a public top-level member (expect the entrypoint) is declared inside a test file.
+
 - [avoid-unnecessary-type-assertions](./common/avoid-unnecessary-type-assertions.md)
 
     Warns about unnecessary usage of 'is' and 'whereType' operators.