Waystone.Monads.FluentValidation 7.3.0

Waystone.Monads.FluentValidation

An interop package for using FluentValidation with Waystone.Monads

Namespaces

The package shadows FluentValidation's own namespaces, so its types sit where a consumer already looks for them rather than under a parallel Waystone tree:

Before v7.0.0 these lived under Waystone.Monads.FluentValidation.*. Only the using directives change; every type and member name is the same. There is no compatibility shim, because a forwarding type in the old namespace would be a different type at run time and a value is ValidationError pattern would silently stop matching.

Supported FluentValidation versions

FluentValidation >= 11.1.0 && < 13.0.0. Bring your own version inside that range; the package does not pin you to one.

The floor is 11.1.0 because that is the first release where ValidationResult.ToDictionary() is an instance method — before it, the same call was an extension method, so a build compiled against 11.1.0 or later fails at run time against an older assembly.

FluentValidation 12 targets net8.0 only, so a consumer on .NET Framework or netstandard2.0 cannot resolve it. That is FluentValidation's constraint, not this package's.

Configuration

This package's options are configured through MonadOptions, so they are set alongside the core options and respect MonadOptions.BeginScope:

MonadOptions.Configure(options => options.UseValidationErrorCode("validation.failed"));

// or scoped to a region of code
using (MonadOptions.BeginScope(options => options.UseValidationErrorCode("debug.validation")))
{
    Result<TestClass, Error> result = value.Validate(new TestClassValidator());
    // the err's code is "debug.validation"
}

The code is read when the validation runs, not when the error is later read.

ValidationError

The Error a validator's failures produce. It derives from Error, so a validation step composes with every other step in a Result chain — there is no conversion at the seam.

Failures carries the ValidationFailure list FluentValidation reported, and is never empty. ToDictionary() groups the messages by property name, ready for a problem-details payload.

if (error is ValidationError validationError)
{
    return ValidationProblem(validationError.ToDictionary());
}

Validate

An extension method that can be invoked on any value (T). Accepts an IValidator<T> which will be executed synchronously.

Example

TestClass value = new();
Result<TestClass, Error> result = value.Validate(new TestClassValidator());

if (result.IsErr)
{
    // validation error
}

ValidateAsync

An extension method that can be invoked on any value (T). Accepts an IValidator<T> which will be executed asynchronously. Returns a ValueTask, so the call composes as a step in an async Result chain.

Example

TestClass value = new();
Result<TestClass, Error> result = await value.ValidateAsync(new TestClassValidator(), CancellationToken.None);

if (result.IsErr)
{
    // validation error
}