Add a New Validation Rule and Flag

Use this skill when you need to add a new validation rule to the dart_skills_lint package, expose it as a toggleable CLI flag, and verify its behavior.

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🛠️ Step-by-Step Implementation

1. Define the Rule in lib/src/rules.dart

To create a new rule, add a top-level CheckType instance.

// lib/src/rules.dart

/// Template instance for checking if the description has a trailing period.
final descriptionTrailingPeriodCheck = CheckType(
  name: 'description-trailing-period',
  defaultSeverity: AnalysisSeverity.error, // or warning/disabled
);

2. Expose the CLI Flag in lib/src/entry_point.dart

Modify runApp to include the toggleable flag for your new rule.

📋 Register Parser Option

Add .addFlag in runApp (around line 60-90):

// lib/src/entry_point.dart

parser
  ..addFlag(descriptionTrailingPeriodCheck.name,
      negatable: true,
      defaultsTo: true,
      help: 'Check if the description ends with a period.');

🎚️ Resolve Flag Logic or Override Severities

Find where severities are evaluated (around line 140-170) and bind your flag state:

if (results.wasParsed(descriptionTrailingPeriodCheck.name)) {
  descriptionTrailingPeriodCheck.severity = (results[descriptionTrailingPeriodCheck.name] as bool)
      ? descriptionTrailingPeriodCheck.defaultSeverity
      : AnalysisSeverity.disabled;
}

Add your rule to the checkTypes set if you want it loaded by default configuration overrides.

3. Implement Validation in lib/src/validator.dart

Write the specific logic inside Validator checking the schema.

// lib/src/validator.dart

void _validateDescriptionPeriod(String description, List<ValidationError> validationErrors) {
  if (description.isNotEmpty && !description.endsWith('.')) {
    validationErrors.add(ValidationError(
      ruleId: _getRule(descriptionTrailingPeriodCheck).name,
      file: _skillFileName,
      message: 'Description must end with a period.',
      severity: _getRule(descriptionTrailingPeriodCheck).severity,
    ));
  }
}

Invoke your sub-routine inside _parseMetadataFields:

final description = yaml[_descriptionField]?.toString() ?? '';
if (description.isNotEmpty) {
  _validateDescriptionPeriod(description, validationErrors);
}

---

🧪 Testing the New Rule

You must write automated tests verifying your rule triggers when it should and skips when it shouldn't.

Creating a Test Suite Case

Add matching suite files in test/ (e.g., test/field_constraints_test.dart or test/metadata_validation_test.dart).

// test/field_constraints_test.dart

test('triggers error when description does not end with period', () async {
  final tempDir = createTempSkillDir(
    name: 'test-skill',
    description: 'This description does not end with a period',
  );

  final validator = Validator(rules: {descriptionTrailingPeriodCheck});
  final result = await validator.validate(tempDir);

  expect(result.validationErrors.any((e) => e.ruleId == 'description-trailing-period'), isTrue);
});
test('skips error when description ends with period', () async {
  final tempDir = createTempSkillDir(
    name: 'test-skill',
    description: 'This description ends with a period.',
  );

  final validator = Validator(rules: {descriptionTrailingPeriodCheck});
  final result = await validator.validate(tempDir);

  expect(result.validationErrors.any((e) => e.ruleId == 'description-trailing-period'), isFalse);
});

---

📚 Documentation Updates

When a new rule is introduced, verify that you synchronize sibling markdown files!

1. README.md:
   • Add your flag under the Usage and Flags sections so users know it exists.
   • Add descriptive lines under Specification Validation.
2. documentation/knowledge/SPECIFICATION.md:
   • If the rule implements standard specifications traits, add constraints parameters under Section 5.1 (Validation parameters).

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🚦 Checklist Before Submitting PR

• Rule defined in rules.dart.
• Flag registered in entry_point.dart.
• Logic implemented in validator.dart.
• Toggle logic tests added in test/.
• Usage listed in README.md.
• Schema documented in documentation/knowledge/SPECIFICATION.md.
• Run dart analyze to ensure no issues.
• Run dart test to ensure tests passing.
• Run dart format . to format code.