feat: add avoid-unnecessary-conditionals rule (#1094)

Author: incendial

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * fix: remove recursive traversal for [`ban-name`](https://dartcodemetrics.dev/docs/rules/common/ban-name) rule.
 * feat: add static code diagnostic [`prefer-using-list-view`](https://dartcodemetrics.dev/docs/rules/flutter/prefer-using-list-view).
+* feat: add static code diagnostic [`avoid-unnecessary-conditionals`](https://dartcodemetrics.dev/docs/rules/common/avoid-unnecessary-conditionals).
 
 ## 5.1.0
 

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

@@ -22,6 +22,7 @@ import 'rules_list/avoid_returning_widgets/avoid_returning_widgets_rule.dart';
 import 'rules_list/avoid_shrink_wrap_in_lists/avoid_shrink_wrap_in_lists_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_conditionals/avoid_unnecessary_conditionals_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';
@@ -96,6 +97,7 @@ final _implementedRules = <String, Rule Function(Map<String, Object>)>{
   AvoidShrinkWrapInListsRule.ruleId: AvoidShrinkWrapInListsRule.new,
   AvoidThrowInCatchBlockRule.ruleId: AvoidThrowInCatchBlockRule.new,
   AvoidTopLevelMembersInTestsRule.ruleId: AvoidTopLevelMembersInTestsRule.new,
+  AvoidUnnecessaryConditionalsRule.ruleId: AvoidUnnecessaryConditionalsRule.new,
   AvoidUnnecessarySetStateRule.ruleId: AvoidUnnecessarySetStateRule.new,
   AvoidUnnecessaryTypeAssertionsRule.ruleId:
       AvoidUnnecessaryTypeAssertionsRule.new,

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_conditionals/avoid_unnecessary_conditionals_rule.dart

@@ -0,0 +1,54 @@
+// 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/replacement.dart';
+import '../../../models/severity.dart';
+import '../../models/common_rule.dart';
+import '../../rule_utils.dart';
+
+part 'visitor.dart';
+
+class AvoidUnnecessaryConditionalsRule extends CommonRule {
+  static const String ruleId = 'avoid-unnecessary-conditionals';
+
+  static const _warning = 'Avoid unnecessary conditional expressions.';
+  static const _correctionMessage =
+      'Remove unnecessary conditional expression.';
+
+  AvoidUnnecessaryConditionalsRule([Map<String, Object> config = const {}])
+      : super(
+          id: ruleId,
+          severity: readSeverity(config, Severity.warning),
+          excludes: readExcludes(config),
+          includes: readIncludes(config),
+        );
+
+  @override
+  Iterable<Issue> check(InternalResolvedUnitResult source) {
+    final visitor = _Visitor();
+
+    source.unit.visitChildren(visitor);
+
+    return visitor.conditionalsInfo
+        .map((info) => createIssue(
+              rule: this,
+              location: nodeLocation(node: info.expression, source: source),
+              message: _warning,
+              replacement: _createReplacement(info),
+            ))
+        .toList(growable: false);
+  }
+
+  Replacement? _createReplacement(_ConditionalInfo info) {
+    final condition = info.expression.condition;
+    final correction = '${info.isInverted ? "!" : ""}$condition';
+
+    return Replacement(comment: _correctionMessage, replacement: correction);
+  }
+}

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

@@ -0,0 +1,35 @@
+part of 'avoid_unnecessary_conditionals_rule.dart';
+
+class _Visitor extends RecursiveAstVisitor<void> {
+  final _conditionalsInfo = <_ConditionalInfo>[];
+
+  Iterable<_ConditionalInfo> get conditionalsInfo => _conditionalsInfo;
+
+  _Visitor();
+
+  @override
+  void visitConditionalExpression(ConditionalExpression node) {
+    super.visitConditionalExpression(node);
+
+    final thenExpression = node.thenExpression;
+    final elseExpression = node.elseExpression;
+
+    if (thenExpression is BooleanLiteral && elseExpression is BooleanLiteral) {
+      final isInverted = !thenExpression.value && elseExpression.value;
+
+      _conditionalsInfo.add(
+        _ConditionalInfo(expression: node, isInverted: isInverted),
+      );
+    }
+  }
+}
+
+class _ConditionalInfo {
+  final ConditionalExpression expression;
+  final bool isInverted;
+
+  const _ConditionalInfo({
+    required this.expression,
+    required this.isInverted,
+  });
+}

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_unnecessary_conditionals/avoid_unnecessary_conditionals_rule_test.dart

@@ -0,0 +1,57 @@
+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_unnecessary_conditionals/avoid_unnecessary_conditionals_rule.dart';
+import 'package:test/test.dart';
+
+import '../../../../../helpers/rule_test_helper.dart';
+
+const _examplePath = 'avoid_unnecessary_conditionals/examples/example.dart';
+
+void main() {
+  group('AvoidUnnecessaryConditionalsRule', () {
+    test('initialization', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_examplePath);
+      final issues = AvoidUnnecessaryConditionalsRule().check(unit);
+
+      RuleTestHelper.verifyInitialization(
+        issues: issues,
+        ruleId: 'avoid-unnecessary-conditionals',
+        severity: Severity.warning,
+      );
+    });
+
+    test('reports about found issues', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_examplePath);
+      final issues = AvoidUnnecessaryConditionalsRule().check(unit);
+
+      RuleTestHelper.verifyIssues(
+        issues: issues,
+        startLines: [7, 13, 16, 18],
+        startColumns: [19, 10, 15, 15],
+        locationTexts: [
+          'str.isEmpty ? true : false',
+          'str.isEmpty ? false : true',
+          'foo ? false : true',
+          'foo ? true : false',
+        ],
+        messages: [
+          'Avoid unnecessary conditional expressions.',
+          'Avoid unnecessary conditional expressions.',
+          'Avoid unnecessary conditional expressions.',
+          'Avoid unnecessary conditional expressions.',
+        ],
+        replacements: [
+          'str.isEmpty',
+          '!str.isEmpty',
+          '!foo',
+          'foo',
+        ],
+        replacementComments: [
+          'Remove unnecessary conditional expression.',
+          'Remove unnecessary conditional expression.',
+          'Remove unnecessary conditional expression.',
+          'Remove unnecessary conditional expression.',
+        ],
+      );
+    });
+  });
+}

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

@@ -0,0 +1,20 @@
+void main() {
+  const str = '';
+
+  final assignment = str.isEmpty ? otherFunction() : bar();
+  final boolean = str.isEmpty ? bar() : baz();
+
+  final another = str.isEmpty ? true : false; // LINT
+}
+
+bool foo() {
+  const str = '';
+
+  return str.isEmpty ? false : true; // LINT
+}
+
+bool bar() => foo ? false : true; // LINT
+
+bool baz() => foo ? true : false; // LINT
+
+String otherFunction() => 'str';

website/docs/rules/common/avoid-unnecessary-conditionals.mdx

@@ -0,0 +1,23 @@
+import RuleDetails from '@site/src/components/RuleDetails';
+
+<RuleDetails version="5.2.0" severity="warning" hasFix />
+
+Checks for unnessesary conditional expressions.
+
+### Example {#example}
+
+**❌ Bad:**
+
+```dart
+bool baz() => foo ? true : false; // LINT
+
+bool bar() => foo ? false : true; // LINT
+```
+
+**✅ Good:**
+
+```dart
+bool baz() => foo;
+
+bool bar() => !foo;
+```

website/docs/rules/index.mdx

@@ -24,8 +24,8 @@ Rules are grouped by category to help you understand their purpose. Each rule ha
   hasConfig
   hasFix
 >
-  Enforces named argument order in function and constructor invocations
-  to be the same as corresponding named parameter declaration order.
+  Enforces named argument order in function and constructor invocations to be
+  the same as corresponding named parameter declaration order.
 </RuleEntry>
 
 <RuleEntry
@@ -182,6 +182,16 @@ Rules are grouped by category to help you understand their purpose. Each rule ha
   inside a test file.
 </RuleEntry>
 
+<RuleEntry
+  name="avoid-unnecessary-conditionals"
+  type="common"
+  severity="warning"
+  version="5.2.0"
+  hasFix
+>
+  Checks for unnessesary conditional expressions.
+</RuleEntry>
+
 <RuleEntry
   name="avoid-unnecessary-type-assertions"
   type="common"
@@ -487,8 +497,8 @@ Rules are grouped by category to help you understand their purpose. Each rule ha
   version="5.1.0"
   hasConfig
 >
-  Suggests to use static class member instead of global constants, variables
-  and functions.
+  Suggests to use static class member instead of global constants, variables and
+  functions.
 </RuleEntry>
 
 <RuleEntry
@@ -654,7 +664,8 @@ Rules are grouped by category to help you understand their purpose. Each rule ha
   severity="performance"
   version="5.2.0"
 >
-  Warns when a <code>Column</code> widget with only <code>children</code> parameter is wrapped in a <code>SingleChildScrollView</code> widget.
+  Warns when a <code>Column</code> widget with only <code>children</code>{' '}
+  parameter is wrapped in a <code>SingleChildScrollView</code> widget.
 </RuleEntry>
 
 ## Intl specific {#intl-specific}