Ignore validation of model property

[NickAb]

Hello,

For implementation of PATCH method where I need to distinguish between property being null or not set, e.g. {"key": null} vs {}.
I have a following model (see below) used to define optional json properties similar to null-able, but it can take any type.
It works for deserialization in tests, but when used inside controller method, then an InvalidOperationException is thrown before my code even runs, because ValidationVisitor from framework iterates over public properties of my model and hits Value property of instance with IsSet==false, which leads to exception.

Is there a way to tell ValidationVisitor to ignore certain property or define a custom validation property?

[JsonConverter(typeof(OptionalJsonConverter))]
public struct Optional<T>
{
    public static Optional<T> Undefined => default(Optional<T>);

    private T _value;

    public Optional(T value)
    {
        IsSet = true;
        _value = value;
    }

    public bool IsSet { get; private set; }

    public T Value
    {
        get
        {
            if (IsSet)
            {
                return _value;
            }
            throw new InvalidOperationException("The value is undefined.");
        }
        set
        {
            IsSet = true;
            _value = value;
        }
    }
}

Here is a stack-trace (minor parts of it is in Russian)

   в WebApi.Optional`1.get_Value() в D:\WebApi\Optional.cs:строка 30
   в Microsoft.Extensions.Internal.PropertyHelper.CallNullSafePropertyGetterByReference[TDeclaringType,TValue](ByRefFunc`2 getter, Object target)
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.DefaultComplexObjectValidationStrategy.Enumerator.MoveNext()
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.VisitChildren(IValidationStrategy strategy)
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.VisitComplexType()
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.Visit(ModelMetadata metadata, String key, Object model)
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.VisitChildren(IValidationStrategy strategy)
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.VisitComplexType()
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.Visit(ModelMetadata metadata, String key, Object model)
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.ValidationVisitor.Validate(ModelMetadata metadata, String key, Object model)
   в Microsoft.AspNet.Mvc.ModelBinding.Validation.DefaultObjectValidator.Validate(IModelValidatorProvider validatorProvider, ModelStateDictionary modelState, ValidationStateDictionary validationState, String prefix, Object model)
   в Microsoft.AspNet.Mvc.Controllers.DefaultControllerActionArgumentBinder.<BindModelAsync>d__6.MoveNext()

[rynowak]

You can do this on RC2 by implementing something similar to https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNetCore.Mvc.Core/ModelBinding/Validation/ValidationExcludeFilter.cs

And then

services.AddMvc(options => 
{
    options.ModelMetadataDetailsProviders.Add(new MyValidationExcludeFilter());
});

This is the mechanism the framework uses to avoid validation recursing into types like XmlDocument or JObject which have deep graphs, but nothing to validate.

The reason you would need to write your own class is that the build in ValidationExcludeFilter doesn't handle generics in the way that you'd want.

[NickAb]

Thanks.

Is attribute based ignore filter in plans or ValidationExcludeFilter will have to be specified in service configuration?
Also, based on link only all instances of type can be ignored, not some of the instances based on some logic (like IsSet not being set). Is it correct and are there any plans to make exclude filters instance aware?

[rynowak]

Also, based on link only all instances of type can be ignored, not some of the instances based on some logic (like IsSet not being set). Is it correct and are there any plans to make exclude filters instance aware?

Yeah, you're right, this isn't really exactly what you're looking for. Reopening.

[Eilon]

Not planned for this release.

[NickAb]

As I understand I can override ValidateNode in ValidationVisitor.cs#L92 and the I will have to implement custom ObjectValidator that inherits from DefaultObjectValidator and replaces visitor in Validate method.
Custom ObjectValidator should be add using DI before calling AddMvc.
Is it correct?

Also, I was wondering I maybe there is a way to affect further validation by editing ValidationContext in first applied validation attribute? Are validation attributes guaranteed to be handled in same order as they applied? And if so, can ValidationContext be edited from one of the attributes to prevent further validation or something like that?

As a note, we still use RC1 as RC2 is not released yet.

[David-Zolv]

Hullo,

I've just found this issue and am facing the same problem.

PATCH method where I need to distinguish between property being null or not set, e.g. {"key": null} vs {}

ASP.NET Core 1.0.0 ("version": "1.0.0-preview2-003121")

Hitting the same validation visitor trying to get the value of my Optional class and getting an exception thrown at it:

   at Utils.Json.OptionalValues.Optional`1.get_Value() in D:\Dev\Utils\Json\OptionalValues\Optional.cs:line 52
   at Microsoft.Extensions.Internal.PropertyHelper.CallNullSafePropertyGetterByReference[TDeclaringType,TValue](ByRefFunc`2 getter, Object target)
   at Microsoft.AspNetCore.Mvc.Internal.DefaultComplexObjectValidationStrategy.Enumerator.MoveNext()
   at Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.VisitChildren(IValidationStrategy strategy)
   at Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.VisitComplexType()
   at Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.Visit(ModelMetadata metadata, String key, Object model)
   at Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.VisitChildren(IValidationStrategy strategy)
   at Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.VisitComplexType()
   at Microsoft.AspNetCore.Mvc.ModelBinding.Validation.ValidationVisitor.Visit(ModelMetadata metadata, String key, Object model)
   at Microsoft.AspNetCore.Mvc.Internal.DefaultControllerArgumentBinder.<BindModelAsync>d__8.MoveNext()

From my Value getter:

public T Value
{
    get
    {
        if (HasValue)
        {
            return _value;
        }

        throw new InvalidOperationException("The value is undefined.");
    }
    set
    {
        HasValue = true;
        _value = value;
    }
}

Is there any update on how to customise the ValidationVisitor to have it check the HasValue property before trying to get the Value? Or as a temporary workaround ignore Optional altogether?

Kind regards,

[dougbu]

Yes, ignore Optional altogether using a regular SuppressChildValidationMetadataProvider (new ValidationExcludeFilter name):

services.AddMvc(options => 
{
    options.ModelMetadataDetailsProviders.Add(
        new SuppressChildValidationMetadataProvider(typeof(Optional)));
});

[NickAb]

But this will ignore all validation of Optional properties. What is desired is to skip property if it was not set and validate it if it was set.

[dougbu]

Your question was

Or as a temporary workaround ignore Optional altogether?

My answer was "yes".

If you want to go further, combine the suppression with custom validation of the Optional type. For example, implement IValidatableObject in Optional and have the Validate(ValidationContext) method make decisions on properties to validate further.

[Eilon]

Closing this bug in favor of #5642, which covers the broader scenarios.