[Bug] OnFieldChanged validates field using validator for owning instance type, not the one for EditContext.Model type

[hakenr]

Describe the bug
Assume we have a complex type from this documentation: https://docs.fluentvalidation.net/en/latest/start.html#complex-properties
There is a Customer class with an Address property and two validators: CustomerValidator and AddressValidator.

Let’s remove this line from the CustomerValidator:

public class CustomerValidator : AbstractValidator<Customer> 
{
  public CustomerValidator()
  {
    RuleFor(customer => customer.Name).NotNull();
-   RuleFor(customer => customer.Address).SetValidator(new AddressValidator());
  }
}

The AddressValidator still exists:

public class AddressValidator : AbstractValidator<Address> 
{
  public AddressValidator()
  {
    RuleFor(address => address.Postcode).NotNull();
    // etc.
  }
}

Now, when you create this type of UI (shortened for brevity):

<EditForm Model="company">
  <FluentValidationValidator />
  <InputText @bind-Value="company.Address.Postcode" />

The FluentValidationValidator validates the Postcode field using the AddressValidator, even though the CompanyValidator for the Model does not reference the AddressValidator, and companyValidator.Validate() does not use the AddressValidator. The Postcode field should not be validated in this case.

Expected behavior
The validator for the Model (CustomerValidator) should be used for all field validations, company.Address.Postcode should not be validated as CustomerValidator does not reference AddressValidator.

Additional context

FluentValidation/src/Blazored.FluentValidation/EditContextFluentValidationExtensions.cs

Lines 84 to 105 in f02c9be

	private static async Task ValidateField(EditContext editContext,
	ValidationMessageStore messages,
	FieldIdentifier fieldIdentifier,
	IServiceProvider serviceProvider,
	bool disableAssemblyScanning,
	IValidator? validator = null)
	{
	var properties = new[] { fieldIdentifier.FieldName };
	var context = new ValidationContext<object>(fieldIdentifier.Model, new PropertyChain(), new MemberNameValidatorSelector(properties));
	validator ??= GetValidatorForModel(serviceProvider, fieldIdentifier.Model, disableAssemblyScanning);
	if (validator is not null)
	{
	var validationResults = await validator.ValidateAsync(context);
	messages.Clear(fieldIdentifier);
	messages.Add(fieldIdentifier, validationResults.Errors.Select(error => error.ErrorMessage));
	editContext.NotifyValidationStateChanged();
	}
	}

I believe the issue is in how the ValidateField() method is implemented. It uses fieldIdentifier.Model directly and does not take editContext.Model into account. The implementation won’t be trivial (you cannot simply replace fieldIdentifier.Model with editContext.Model as someone has already tried), but it is doable.

Related items:

• [Bug] Nested Complex Type Validation Fails #76
• Passing parent model instead of nested type to resolve exception thrown by FluentValidation #91
• [Bug] Validations not working as expected. #104
• Reverted ValidateField to use FieldIdentifier.Model #132
• ValidateField: fieldIdentifier.Model different to editContext.Model #178

cc @jirikanda

[hakenr]

Also seems to be related:

• [Bug] Inconsistent model-level and field-level behaviour for sub-objects #204