fluentvalidation-command-arguments

Command Argument Validation with FluentValidation

SlashCommands MUST use FluentValidation for argument validation via Spectre.Console.CLI's validation pattern.

DO:

• •Create validator classes alongside settings classes (e.g., StoryCommandSettingsValidator)
• •Inherit validators from AbstractValidator<TSettings>
• •Define validation rules in the validator constructor
• •Override Validate() in settings class to instantiate validator and return ValidationResult
• •Map FluentValidation errors to ValidationResult.Error(message)

DON'T:

• •Perform validation in ExecuteAsync method with manual conditionals
• •Use DataAnnotations attributes for complex cross-property validation
• •Build custom validation frameworks

Example Pattern:

public override ValidationResult Validate()
{
    var validator = new StoryCommandSettingsValidator();
    var result = validator.Validate(this);
    return result.IsValid 
        ? ValidationResult.Success() 
        : ValidationResult.Error(result.Errors.First().ErrorMessage);
}

Rationale: Consistent validation improves maintainability; FluentValidation provides expressive, readable rules for complex scenarios like mutually exclusive flags.