feat: add avoid-shrink-wrap-in-lists (#918)

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-shrink-wrap-in-lists`](https://dartcodemetrics.dev/docs/rules/flutter/avoid-shrink-wrap-in-lists).
 * 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-correct-edge-insets-constructor-rule`](https://dartcodemetrics.dev/docs/rules/flutter/prefer-correct-edge-insets-constructor).
 * feat: add static code diagnostic [`prefer-enums-by-name`](https://dartcodemetrics.dev/docs/rules/common/prefer-enums-by-name).

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

@@ -15,6 +15,7 @@ import 'rules_list/avoid_non_ascii_symbols/avoid_non_ascii_symbols_rule.dart';
 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_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_setstate/avoid_unnecessary_setstate_rule.dart';
@@ -77,6 +78,7 @@ final _implementedRules = <String, Rule Function(Map<String, Object>)>{
   AvoidNonNullAssertionRule.ruleId: AvoidNonNullAssertionRule.new,
   AvoidPreserveWhitespaceFalseRule.ruleId: AvoidPreserveWhitespaceFalseRule.new,
   AvoidReturningWidgetsRule.ruleId: AvoidReturningWidgetsRule.new,
+  AvoidShrinkWrapInListsRule.ruleId: AvoidShrinkWrapInListsRule.new,
   AvoidThrowInCatchBlockRule.ruleId: AvoidThrowInCatchBlockRule.new,
   AvoidTopLevelMembersInTestsRule.ruleId: AvoidTopLevelMembersInTestsRule.new,
   AvoidUnnecessarySetStateRule.ruleId: AvoidUnnecessarySetStateRule.new,

lib/src/analyzers/lint_analyzer/rules/rules_list/avoid_shrink_wrap_in_lists/avoid_shrink_wrap_in_lists_rule.dart

@@ -0,0 +1,48 @@
+// ignore_for_file: public_member_api_docs
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:collection/collection.dart';
+
+import '../../../../../utils/flutter_types_utils.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/flutter_rule.dart';
+import '../../rule_utils.dart';
+
+part 'visitor.dart';
+
+class AvoidShrinkWrapInListsRule extends FlutterRule {
+  static const String ruleId = 'avoid-shrink-wrap-in-lists';
+
+  static const _warning =
+      'Avoid using ListView with shrinkWrap, since it might degrade the performance. Consider using slivers instead.';
+
+  AvoidShrinkWrapInListsRule([Map<String, Object> config = const {}])
+      : super(
+          id: ruleId,
+          severity: readSeverity(config, Severity.performance),
+          excludes: readExcludes(config),
+        );
+
+  @override
+  Iterable<Issue> check(InternalResolvedUnitResult source) {
+    final visitor = _Visitor();
+
+    source.unit.visitChildren(visitor);
+
+    return visitor.expressions
+        .map((expression) => createIssue(
+              rule: this,
+              location: nodeLocation(
+                node: expression,
+                source: source,
+              ),
+              message: _warning,
+            ))
+        .toList(growable: false);
+  }
+}

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

@@ -0,0 +1,33 @@
+part of 'avoid_shrink_wrap_in_lists_rule.dart';
+
+class _Visitor extends RecursiveAstVisitor<void> {
+  final _expressions = <Expression>[];
+
+  Iterable<Expression> get expressions => _expressions;
+
+  @override
+  void visitInstanceCreationExpression(InstanceCreationExpression node) {
+    super.visitInstanceCreationExpression(node);
+
+    if (isListViewWidget(node.staticType) &&
+        _hasShrinkWrap(node) &&
+        _hasParentList(node)) {
+      _expressions.add(node);
+    }
+  }
+
+  bool _hasShrinkWrap(InstanceCreationExpression node) =>
+      node.argumentList.arguments.firstWhereOrNull(
+        (arg) => arg is NamedExpression && arg.name.label.name == 'shrinkWrap',
+      ) !=
+      null;
+
+  bool _hasParentList(InstanceCreationExpression node) =>
+      node.thisOrAncestorMatching((parent) =>
+          parent != node &&
+          parent is InstanceCreationExpression &&
+          (isListViewWidget(parent.staticType) ||
+              isColumnWidget(parent.staticType) ||
+              isRowWidget(parent.staticType))) !=
+      null;
+}

lib/src/utils/flutter_types_utils.dart

@@ -18,15 +18,24 @@ bool isWidgetStateOrSubclass(DartType? type) =>
 bool isSubclassOfListenable(DartType? type) =>
     type is InterfaceType && type.allSupertypes.any(_isListenable);
 
+bool isListViewWidget(DartType? type) =>
+    type?.getDisplayString(withNullability: false) == 'ListView';
+
+bool isColumnWidget(DartType? type) =>
+    type?.getDisplayString(withNullability: false) == 'Column';
+
+bool isRowWidget(DartType? type) =>
+    type?.getDisplayString(withNullability: false) == 'Row';
+
 bool isPaddingWidget(DartType? type) =>
     type?.getDisplayString(withNullability: false) == 'Padding';
 
-bool _isWidget(DartType? type) =>
-    type?.getDisplayString(withNullability: false) == 'Widget';
-
 bool isBuildContext(DartType? type) =>
     type?.getDisplayString(withNullability: false) == 'BuildContext';
 
+bool _isWidget(DartType? type) =>
+    type?.getDisplayString(withNullability: false) == 'Widget';
+
 bool _isSubclassOfWidget(DartType? type) =>
     type is InterfaceType && type.allSupertypes.any(_isWidget);
 

test/src/analyzers/lint_analyzer/rules/rules_list/avoid_shrink_wrap_in_lists/avoid_shrink_wrap_in_lists_rule_test.dart

@@ -0,0 +1,43 @@
+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_shrink_wrap_in_lists/avoid_shrink_wrap_in_lists_rule.dart';
+import 'package:test/test.dart';
+
+import '../../../../../helpers/rule_test_helper.dart';
+
+const _examplePath = 'avoid_shrink_wrap_in_lists/examples/example.dart';
+
+void main() {
+  group('AvoidShrinkWrapInListsRule', () {
+    test('initialization', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_examplePath);
+      final issues = AvoidShrinkWrapInListsRule().check(unit);
+
+      RuleTestHelper.verifyInitialization(
+        issues: issues,
+        ruleId: 'avoid-shrink-wrap-in-lists',
+        severity: Severity.performance,
+      );
+    });
+
+    test('reports about found issues', () async {
+      final unit = await RuleTestHelper.resolveFromFile(_examplePath);
+      final issues = AvoidShrinkWrapInListsRule().check(unit);
+
+      RuleTestHelper.verifyIssues(
+        issues: issues,
+        startLines: [10, 17, 24],
+        startColumns: [30, 27, 32],
+        locationTexts: [
+          'ListView(shrinkWrap: true, children: [])',
+          'ListView(shrinkWrap: true, children: [])',
+          'ListView(shrinkWrap: true, children: [])',
+        ],
+        messages: [
+          'Avoid using ListView with shrinkWrap, since it might degrade the performance. Consider using slivers instead.',
+          'Avoid using ListView with shrinkWrap, since it might degrade the performance. Consider using slivers instead.',
+          'Avoid using ListView with shrinkWrap, since it might degrade the performance. Consider using slivers instead.',
+        ],
+      );
+    });
+  });
+}

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

@@ -0,0 +1,47 @@
+class CoolWidget {
+  Widget build() {
+    return ListView(child: Widget());
+  }
+}
+
+class WidgetWithColumn {
+  Widget build() {
+    // LINT
+    return Column(children: [ListView(shrinkWrap: true, children: [])]);
+  }
+}
+
+class WidgetWithRow {
+  Widget build() {
+    // LINT
+    return Row(children: [ListView(shrinkWrap: true, children: [])]);
+  }
+}
+
+class WidgetWithList {
+  Widget build() {
+    // LINT
+    return ListView(children: [ListView(shrinkWrap: true, children: [])]);
+  }
+}
+
+class ListView extends Widget {
+  final bool shrinkWrap;
+  final List<Widget> children;
+
+  const ListView({required this.shrinkWrap, required this.children});
+}
+
+class Column extends Widget {
+  final List<Widget> children;
+
+  const Column({required this.children});
+}
+
+class Row extends Widget {
+  final List<Widget> children;
+
+  const Row({required this.children});
+}
+
+class Widget {}

website/docs/rules/flutter/avoid-shrink-wrap-in-lists.md

@@ -0,0 +1,53 @@
+# Avoid shrink wrap in lists
+
+## Rule id {#rule-id}
+
+avoid-shrink-wrap-in-lists
+
+## Severity {#severity}
+
+Performance
+
+## Description {#description}
+
+Warns when a `ListView` widget with `shrinkWrap` parameter is wrapped in a `Column`, `Row` or another `ListView` widget.
+
+According to the Flutter documentation, using `shrinkWrap` in lists is expensive performance-wise and should be avoided, since using slivers is significantly cheaper and achieves the same or even better results.
+
+Additional resources:
+
+- <https://github.com/dart-lang/linter/issues/3496>
+
+### Example {#example}
+
+Bad:
+
+```dart
+Column(
+  children: [
+    Expanded(
+      // LINT
+      child: ListView(
+        shrinkWrap: true,
+        physics: const NeverScrollableScrollPhysics(),
+        children: [],
+      ),
+    ),
+  ],
+),
+```
+
+Good:
+
+```dart
+CustomScrollView(
+  slivers: [
+    SliverList(
+      delegate: SliverChildBuilderDelegate(
+        (context, index) => Container(),
+        childCount: someObject.length,
+      ),
+    ),
+  ],
+),
+```