rules.md

ValSan rules() Feature

The rules() method is a core feature of the ValSan validation framework. It allows each validator to declare its validation rules in a structured, discoverable way.

What is rules()?

• rules() is a method you define on your ValSan class.
• It returns an object (a RuleSet) where each key is a rule code and each value is a Rule object.
• Each Rule describes a validation condition, error message, and optional helper text.

Why use rules()?

• Discoverable rules

Example

class NoSpacesValSan extends ValSan<string, string> {
  override rules() {
    return {
      no_spaces: {
        code: 'no_spaces',
        user: {
          errorMessage: 'No spaces allowed',
          helperText: 'Enter a value without spaces',
        },
      },
    };
  }

  async validate(input: string) {
    if (input.includes(' ')) {
      return this.fail([this.rules().no_spaces]);
    }
    return this.pass();
  }
}

Rule Object Structure

• code: Unique string identifier for the rule (lowercase, snake_case recommended)
• user: Object with helperText and errorMessage (shown to users)
• dev: (optional) Object with developer-facing help text & error message

Best Practices

• Always use lowercase, descriptive codes
• Keep error messages clear and actionable
• Use rules() for all dynamic error context/messages

See the main documentation for more advanced usage and patterns.