Add linter rule to disallow string literals in Widget classes

packages/leancode_lint/lib/leancode_lint.dart

@@ -5,6 +5,7 @@ import 'package:leancode_lint/assists/convert_record_into_nominal_type.dart';
 import 'package:leancode_lint/lints/add_cubit_suffix_for_cubits.dart';
 import 'package:leancode_lint/lints/avoid_conditional_hooks.dart';
 import 'package:leancode_lint/lints/avoid_single_child_in_multi_child_widget.dart';
+import 'package:leancode_lint/lints/avoid_string_literals_in_widgets.dart';
 import 'package:leancode_lint/lints/catch_parameter_names.dart';
 import 'package:leancode_lint/lints/constructor_parameters_and_fields_should_have_the_same_order.dart';
 import 'package:leancode_lint/lints/hook_widget_does_not_use_hooks.dart';
@@ -26,6 +27,7 @@ class _Linter extends PluginBase {
         HookWidgetDoesNotUseHooks(),
         ConstructorParametersAndFieldsShouldHaveTheSameOrder(),
         AvoidSingleChildInMultiChildWidgets(),
+        AvoidStringLiteralsInWidgets(),
       ];
 
   @override

packages/leancode_lint/lib/lints/avoid_string_literals_in_widgets.dart

@@ -0,0 +1,71 @@
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:analyzer/error/listener.dart';
+import 'package:custom_lint_builder/custom_lint_builder.dart';
+import 'package:leancode_lint/helpers.dart';
+
+/// Displays warning for string literals used inside Widget classes.
+class AvoidStringLiteralsInWidgets extends DartLintRule {
+  AvoidStringLiteralsInWidgets() : super(code: _getLintCode());
+
+  static const ruleName = 'avoid_string_literals_in_widgets';
+
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ErrorReporter reporter,
+    CustomLintContext context,
+  ) {
+    context.registry.addClassDeclaration(
+      (node) {
+        final isThisWidgetClass = isWidgetClass(node);
+        if (!isThisWidgetClass) {
+          return;
+        }
+
+        final stringLiterals = _getDescendantStringLiterals(node);
+
+        for (final stringLiteral in stringLiterals) {
+          reporter.reportErrorForNode(_getLintCode(), stringLiteral);
+        }
+      },
+    );
+  }
+
+  static List<AstNode> _getDescendantStringLiterals(
+    AstNode node,
+  ) {
+    final stringLiterals = <StringLiteral>[];
+    node.visitChildren(_StringLiteralVisitor(stringLiterals));
+    return stringLiterals;
+  }
+
+  static LintCode _getLintCode() {
+    return const LintCode(
+      name: ruleName,
+      problemMessage: 'Do not use string literals in widgets.',
+      correctionMessage: 'Prefer a localized message.',
+      errorSeverity: ErrorSeverity.WARNING,
+    );
+  }
+}
+
+class _StringLiteralVisitor extends GeneralizingAstVisitor<void> {
+  _StringLiteralVisitor(this.acc);
+
+  final List<StringLiteral> acc;
+
+  @override
+  void visitStringLiteral(StringLiteral node) {
+    final insideCatchClause =
+        node.thisOrAncestorMatching((n) => n is CatchClause) != null;
+    final insideThrowExpression =
+        node.thisOrAncestorMatching((n) => n is ThrowExpression) != null;
+    if (!insideCatchClause && !insideThrowExpression) {
+      acc.add(node);
+    }
+
+    super.visitStringLiteral(node);
+  }
+}

packages/leancode_lint/test/lints_test_app/lib/avoid_conditional_hooks_test.dart

@@ -1,3 +1,5 @@
+// ignore_for_file: avoid_string_literals_in_widgets
+
 import 'dart:math';
 
 import 'package:flutter/material.dart';

packages/leancode_lint/test/lints_test_app/lib/avoid_string_literals_in_widgets_test.dart

@@ -0,0 +1,47 @@
+// ignore_for_file: avoid_print
+
+import 'package:flutter/material.dart';
+
+class MyStatelessWidget extends StatelessWidget {
+  const MyStatelessWidget({super.key});
+
+  // expect_lint: avoid_string_literals_in_widgets
+  final aStringVariable = 'This is an hardcoded text';
+
+  // expect_lint: avoid_string_literals_in_widgets
+  final anInterpolatedStringVariable = 'This is a number: ${1}';
+
+  @override
+  Widget build(BuildContext context) {
+    try {
+      // expect_lint: avoid_string_literals_in_widgets
+      print('Executing something...');
+      _doSomethingBad();
+    } catch (err) {
+      print('Something bad happened.');
+    }
+
+    return Column(
+      children: [
+        // expect_lint: avoid_string_literals_in_widgets
+        const WidgetWithText('This is an hardcoded text'),
+        WidgetWithText(aStringVariable),
+      ],
+    );
+  }
+
+  void _doSomethingBad() {
+    throw Exception('Bad stuff happening');
+  }
+}
+
+class WidgetWithText extends StatelessWidget {
+  const WidgetWithText(this.text, {super.key});
+
+  final String text;
+
+  @override
+  Widget build(BuildContext context) {
+    return Container();
+  }
+}

packages/leancode_lint/test/lints_test_app/lib/hook_widget_does_not_use_hooks_test.dart

@@ -1,3 +1,5 @@
+// ignore_for_file: avoid_string_literals_in_widgets
+
 import 'package:flutter/material.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';

packages/leancode_lint/test/lints_test_app/lib/use_design_system_item_test.dart

@@ -1,4 +1,5 @@
 // ignore_for_file: unused_local_variable
+// ignore_for_file: avoid_string_literals_in_widgets
 
 import 'package:flutter/material.dart';