NDLRGEN018: Validator won't run¶

Cause¶

A Validator is specified but ValidateOnStart is false, so the validator will never be invoked.

Rule Description¶

When you specify [Options(Validator = typeof(...))] but don't set ValidateOnStart = true, the validator is registered but never actually called. This is likely a configuration mistake.

This is a warning because the code is technically valid, but probably not what you intended.

How to Fix¶

Either enable validation or remove the validator:

// ⚠️ Warning - validator specified but won't run
[Options(Validator = typeof(MyValidator))]  // ValidateOnStart defaults to false
public class MyOptions { }

// ✅ Option 1: Enable ValidateOnStart
[Options(Validator = typeof(MyValidator), ValidateOnStart = true)]
public class MyOptions { }

// ✅ Option 2: Remove the unused Validator
[Options]
public class MyOptions { }

Example¶

Code with Warning¶

using NexusLabs.Needlr.Generators;

// NDLRGEN018: Validator 'PaymentOptionsValidator' will not run 
//             because ValidateOnStart is false
[Options(Validator = typeof(PaymentOptionsValidator))]
public class PaymentOptions
{
    public string MerchantId { get; set; } = "";
}

public class PaymentOptionsValidator : IOptionsValidator<PaymentOptions>
{
    public IEnumerable<ValidationError> Validate(PaymentOptions options)
    {
        if (string.IsNullOrEmpty(options.MerchantId))
            yield return "MerchantId is required";
    }
}

Fixed Code¶

using NexusLabs.Needlr.Generators;

// ✅ ValidateOnStart = true enables the validator
[Options(Validator = typeof(PaymentOptionsValidator), ValidateOnStart = true)]
public class PaymentOptions
{
    public string MerchantId { get; set; } = "";
}

public class PaymentOptionsValidator : IOptionsValidator<PaymentOptions>
{
    public IEnumerable<ValidationError> Validate(PaymentOptions options)
    {
        if (string.IsNullOrEmpty(options.MerchantId))
            yield return "MerchantId is required";
    }
}

Why This Warning Exists¶

Specifying a validator without enabling validation is almost always a mistake:

You wrote validation logic that will never execute
Your application won't fail fast on invalid configuration
Future maintainers may assume validation is happening

Suppressing the Warning¶

If you intentionally want to specify a validator without running it at startup (e.g., for manual validation later), suppress the warning:

#pragma warning disable NDLRGEN018
[Options(Validator = typeof(MyValidator))]
public class MyOptions { }
#pragma warning restore NDLRGEN018

Or in .editorconfig:

[*.cs]
dotnet_diagnostic.NDLRGEN018.severity = none