feat: Add low_readability_numeric_literals lint rule and quick fix (#210

)

melos.yaml

@@ -75,11 +75,13 @@ scripts:
     description: format (dry-run)
 
   fmt:dart:
-    run: melos exec -c 1 --fail-fast -- dart format .
+    # https://github.com/dart-lang/sdk/issues/59815
+    run: melos exec -c 1 --fail-fast -- dart format --enable-experiment=digit-separators .
     description: format dart
 
   fmt:dart:dry:
-    run: melos exec -c 1 --fail-fast -- dart format --set-exit-if-changed .
+    # https://github.com/dart-lang/sdk/issues/59815
+    run: melos exec -c 1 --fail-fast -- dart format --set-exit-if-changed --enable-experiment=digit-separators .
     description: format dart (dry-run)
 
   fix:

packages/nilts/README.md

@@ -101,6 +101,7 @@ Some of lint rules support quick fixes on IDE.
 | [defined\_void\_callback\_type](#defined_void_callback_type)                        | Checks `void Function()` definitions.                                          |  Any versions nilts supports   | Practice  |  Experimental  |    ✅️     |
 | [fixed\_text\_scale\_rich\_text](#fixed_text_scale_rich_text)                       | Checks usage of `textScaler` or `textScaleFactor` in `RichText` constructor.   |  Any versions nilts supports   | Practice  |  Experimental  |    ✅️     |
 | [flaky\_tests\_with\_set\_up\_all](#flaky_tests_with_set_up_all)                    | Checks `setUpAll` usages.                                                      |  Any versions nilts supports   | Practice  |  Experimental  |    ✅️     |
+| [low\_readability\_numeric\_literals](#low_readability_numeric_literals)            | Checks numeric literals with 5 or more digits.                                 | >= Flutter 3.27.0 (Dart 3.6.0) | Practice  |  Experimental  |    ✅️     |
 | [no\_support\_multi\_text\_direction](#no_support_multi_text_direction)             | Checks if supports `TextDirection` changes.                                    |  Any versions nilts supports   | Practice  |  Experimental  |    ✅️     |
 | [no\_support\_web\_platform\_check](#no_support_web_platform_check)                 | Checks if `Platform.isXxx` usages.                                             |  Any versions nilts supports   | Practice  |  Experimental  |    ✅️     |
 | [shrink\_wrapped\_scroll\_view](#shrink_wrapped_scroll_view)                        | Checks the content of the scroll view is shrink wrapped.                       |  Any versions nilts supports   | Practice  |  Experimental  |    ✅️     |
@@ -412,6 +413,34 @@ See also:
 
 </details>
 
+#### low_readability_numeric_literals
+
+<details>
+
+- Target SDK     : >= Flutter 3.27.0 (Dart 3.6.0)
+- Rule type      : Practice
+- Maturity level : Experimental
+- Quick fix      : ✅
+
+**Consider** using digit separators for numeric literals with 5 or more digits to improve readability.
+
+**BAD:**
+```dart
+const int value = 123456;
+```
+
+**GOOD:**
+```dart
+const int value = 123_456;
+```
+
+See also:
+
+- [Digit Separators in Dart 3.6](https://medium.com/dartlang/announcing-dart-3-6-778dd7a80983)
+- [Built-in types | Dart](https://dart.dev/language/built-in-types#numbers)
+
+</details>
+
 #### no_support_multi_text_direction
 
 <details>

packages/nilts/lib/nilts.dart

@@ -8,6 +8,7 @@ import 'package:nilts/src/lints/defined_value_getter_type.dart';
 import 'package:nilts/src/lints/defined_void_callback_type.dart';
 import 'package:nilts/src/lints/fixed_text_scale_rich_text.dart';
 import 'package:nilts/src/lints/flaky_tests_with_set_up_all.dart';
+import 'package:nilts/src/lints/low_readability_numeric_literals.dart';
 import 'package:nilts/src/lints/no_support_multi_text_direction.dart';
 import 'package:nilts/src/lints/no_support_web_platform_check.dart';
 import 'package:nilts/src/lints/shrink_wrapped_scroll_view.dart';
@@ -35,6 +36,8 @@ class _NiltsLint extends PluginBase {
         else
           const FixedTextScaleRichTextLegacy(),
         const FlakyTestsWithSetUpAll(),
+        if (_dartVersion >= const DartVersion(major: 3, minor: 6, patch: 0))
+          const LowReadabilityNumericLiterals(),
         const NoSupportMultiTextDirection(),
         const NoSupportWebPlatformCheck(),
         const ShrinkWrappedScrollView(),

packages/nilts/lib/src/change_priority.dart

@@ -8,6 +8,9 @@
 /// See also:
 ///   - [IgnoreCode](https://github.com/invertase/dart_custom_lint/blob/1df2851a80ccdc5a2bda4418006560f49c03b8ec/packages/custom_lint_builder/lib/src/ignore.dart#L102)
 class ChangePriority {
+  /// The priority for [_AddDigitSeparators]
+  static const int addDigitSeparators = 100;
+
   /// The priority for [_AddTextScaleFactor].
   static const int addTextScaleFactor = 90;
 

packages/nilts/lib/src/lints/low_readability_numeric_literals.dart

@@ -0,0 +1,114 @@
+import 'package:analyzer/error/error.dart' as analyzer;
+import 'package:analyzer/error/listener.dart';
+import 'package:custom_lint_builder/custom_lint_builder.dart';
+import 'package:nilts/src/change_priority.dart';
+
+/// A class for `low_readability_numeric_literals` rule.
+///
+/// This rule checks numeric literals with 5 or more digits.
+///
+/// - Target SDK     : >= Flutter 3.27.0 (Dart 3.6.0)
+/// - Rule type      : Practice
+/// - Maturity level : Experimental
+/// - Quick fix      : ✅
+///
+/// **Consider** using digit separators for numeric literals with 5 or more
+/// digits to improve readability.
+///
+/// **BAD:**
+/// ```dart
+/// const int value = 123456;
+/// ```
+///
+/// **GOOD:**
+/// ```dart
+/// const int value = 123_456;
+/// ```
+///
+/// See also:
+///
+/// - [Digit Separators in Dart 3.6](https://medium.com/dartlang/announcing-dart-3-6-778dd7a80983)
+/// - [Built-in types | Dart](https://dart.dev/language/built-in-types#numbers)
+class LowReadabilityNumericLiterals extends DartLintRule {
+  /// Creates a new instance of [LowReadabilityNumericLiterals].
+  const LowReadabilityNumericLiterals() : super(code: _code);
+
+  static const _code = LintCode(
+    name: 'low_readability_numeric_literals',
+    problemMessage:
+        'Numeric literals with 5 or more digits should use digit separators '
+        'for better readability.',
+    url: 'https://github.com/ronnnnn/nilts#low_readability_numeric_literals',
+  );
+
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ErrorReporter reporter,
+    CustomLintContext context,
+  ) {
+    context.registry.addIntegerLiteral((node) {
+      final value = node.value;
+      if (value == null) return;
+
+      final literal = node.literal.lexeme;
+      if (literal.contains('_')) return;
+
+      if (value.abs() >= 10000) {
+        reporter.atNode(node, _code);
+      }
+    });
+  }
+
+  @override
+  List<Fix> getFixes() => [
+        _AddDigitSeparators(),
+      ];
+}
+
+class _AddDigitSeparators extends DartFix {
+  @override
+  void run(
+    CustomLintResolver resolver,
+    ChangeReporter reporter,
+    CustomLintContext context,
+    analyzer.AnalysisError analysisError,
+    List<analyzer.AnalysisError> others,
+  ) {
+    context.registry.addIntegerLiteral((node) {
+      if (!node.sourceRange.intersects(analysisError.sourceRange)) return;
+
+      final value = node.value;
+      if (value == null) return;
+
+      final literal = node.literal.lexeme;
+      if (literal.contains('_')) return;
+
+      reporter
+          .createChangeBuilder(
+        message: 'Add digit separators',
+        priority: ChangePriority.addDigitSeparators,
+      )
+          .addDartFileEdit((builder) {
+        final newLiteral = _addSeparators(literal);
+        builder.addSimpleReplacement(node.sourceRange, newLiteral);
+      });
+    });
+  }
+
+  String _addSeparators(String literal) {
+    final buffer = StringBuffer();
+    var count = 0;
+
+    for (var i = literal.length - 1; i >= 0; i--) {
+      buffer.write(literal[i]);
+      count++;
+      if (count == 3 && i != 0) {
+        buffer.write('_');
+        count = 0;
+      }
+    }
+
+    return buffer.toString().split('').reversed.join();
+  }
+}

packages/nilts_test/pubspec.yaml

@@ -3,8 +3,8 @@ description: A new Flutter module project.
 publish_to: 'none'
 
 environment:
-  sdk: '>=3.0.0 <4.0.0'
-  flutter: '>=3.10.0'
+  sdk: '>=3.6.0 <4.0.0'
+  flutter: '>=3.27.1'
 
 dependencies:
   flutter:

packages/nilts_test/test/lints/low_readability_numeric_literals.dart

@@ -0,0 +1,63 @@
+// ignore_for_file: avoid_js_rounded_ints
+// ignore_for_file: prefer_const_declarations
+// ignore_for_file: prefer_final_locals
+// ignore_for_file: unused_element
+// ignore_for_file: unused_local_variable
+
+const _globalConstant1 = 1234;
+// expect_lint: low_readability_numeric_literals
+const _globalConstant2 = 12345;
+
+var _globalVariable1 = 1234;
+// expect_lint: low_readability_numeric_literals
+var _globalVariable2 = 12345;
+
+final _globalFinal1 = 1234;
+// expect_lint: low_readability_numeric_literals
+final _globalFinal2 = 12345;
+
+void main() {
+  const constant1 = 1234;
+  // expect_lint: low_readability_numeric_literals
+  const constant2 = 12345;
+  const constant3 = 12_345;
+  // expect_lint: low_readability_numeric_literals
+  const constant4 = 1234567890;
+  const constant5 = 1_234_567_890;
+  // expect_lint: low_readability_numeric_literals
+  const constant6 = 123456789012345;
+  const constant7 = 123_456_789_012_345;
+
+  var variable1 = 1234;
+  // expect_lint: low_readability_numeric_literals
+  var variable2 = 12345;
+  var variable3 = 12_345;
+  // expect_lint: low_readability_numeric_literals
+  var variable4 = 1234567890;
+  var variable5 = 1_234_567_890;
+  // expect_lint: low_readability_numeric_literals
+  var variable6 = 123456789012345;
+  var variable7 = 123_456_789_012_345;
+
+  final final1 = 1234;
+  // expect_lint: low_readability_numeric_literals
+  final final2 = 12345;
+  final final3 = 12_345;
+  // expect_lint: low_readability_numeric_literals
+  final final4 = 1234567890;
+  final final5 = 1_234_567_890;
+  // expect_lint: low_readability_numeric_literals
+  final final6 = 123456789012345;
+  final final7 = 123_456_789_012_345;
+
+  const hex1 = 0x1234;
+  // expect_lint: low_readability_numeric_literals
+  const hex2 = 0x12345;
+  const hex3 = 0x12_345;
+  // expect_lint: low_readability_numeric_literals
+  const hex4 = 0x1234567890;
+  const hex5 = 0x1_234_567_890;
+  // expect_lint: low_readability_numeric_literals
+  const hex6 = 0x123456789012345;
+  const hex7 = 0x123_456_789_012_345;
+}

pubspec.yaml

@@ -2,7 +2,7 @@ name: nilts_workspace
 publish_to: 'none'
 
 environment:
-  sdk: '>=3.0.0 <4.0.0'
+  sdk: '>=3.6.0 <4.0.0'
 
 dev_dependencies:
   melos: ^6.2.0