Valigator

• Concepts
  • Value Validator
  • State Validator
  • Validation Error Format
• Valigator Packages
  • Valigator.Core
  • Valigator.AspNetCore
• Usage
• Random Things To Move to Better Places
  • Custom Validations
• Gotchas

Valigator is .NET suite of libraries that enabled the declaration of complex validation rules directly on model properties.

Concepts

Valigator.AspNetCore provides a JsonConverter and attaches to the AspNetCore deserialization process.

Any model to be validated by Valigator must have the [ValigatorModel] attribute. This will result in any property decorated by the Data<T> being validated by the converter.

Usage of the Data<T> decorator is governed by a few rules:

• All properties must have a declared setter. This setter may be private.

• Data must be one of Required, Optional, or Defaulted

  • Required
    • A value must be provided.
    • If a value is not provided, an error is produced.
    • Whether this is nullable or not is dictated by nullability (See XXXXX below).
    • This value is stored in Data<T>
    • Example:

    Data<int> RequiredInt { get; set; } = Data.Required<int>().GreaterThan(1);

  • Optional
    • A value does not need to be provided.
    • If a vlaue is not provided, Option.None<T> is produced.
    • Whether this is nullable or not is dictated by nullability (See XXXXX below).
    • This value is stored in Data<Option<T>>
    • Example:

    Data<Option<int>> OptionalInt { get; set; } = Data.Optional<int>().GreaterThan(1);

  • Defaulted
    • A value does not need to be provided.
    • When a value is not provided, a default value is used instead.
    • Whether this is nullable or not is dictated by nullability (See XXXXX below).
    • This value is stored in Data<T>
    • Example:

    public Data<int> DefaultedInt { get; set; } = Data.Defaulted<int>(3).GreaterThan(1);

• Nullability means that null is a valid input value

  • Nullable value are indicated by adding Nullable().
    • Nullable Required means that a value must be provided, but it can be null.
    • Nullable Optional means that a value does not need to be provided, but if it is, it may be null.
    • Nullable Default means that a value does not need to be provided, but if it is, it may be null.
  • Nullable implies Option<T>
  • A nullable collection means that the collection itself may be null
  • TODO: Items Nullable Information
  • Examples:

  public Data<Option<int>> NullableRequiredInt { get; set; } = Data.Required<int>().Nullable().GreaterThan(1);

• Collections are defined slightly differently than regular Data fields.

  public Data<int[]> RequiredIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).Required();
  
  public Data<int[]> DefaultedIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).Defaulted(new[]{1, 2, 3});
  
  public Data<int[]> DefaultEmptyIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).DefaultedToEmpty();
  
  public Data<Option<int[]>> OptionalIntegerCollection { get; set; } = Data.Collection<int>(x => x.GreaterThan(1)).Optional();

• Validating Non-Data Fields Apply the [ValidateContents] attribute to the property or field to be validated. This will cause Valigator to run validations upon whatever object is contained in this field or property.

  Example:

  [ValidateContents]
  private readonly object _value;

• Any anonymous type with Valigator properties (properties of type Data<T>) must be converted to a ValigatorModel<T>. The easiest way to do this is to use the .ToValigatorModel() extension method from Valigator.Newtonsoft.Json.

  new { Type = "A Type", UnitCost = Data.Require<int>() }.ToValigatorModel()

When a Valigator model is deserialized, it deserializes into one of two states:

• Set - Data was provided and passes all validations
• Unset - No data was provided. This is equivalent to skipping a field. Passing in null is not Unset, that is either Valid or Invalid.

Value Validator

State Validator

Validation Error Format

Valigator Packages

Valigator.Core

The core library of Valigator.

Valigator.AspNetCore

Library specifically to make adding to an AspNetCore application easy.

Usage

• Install the appropriate Valigator packages from the list above.
• In configure Valigator service

  public void ConfigureServices(IServiceCollection services)
  {
      services
          .AddValigator(InputErrorHandler, OutputErrorHandler);
  }

• Add the input error handler. This handler will be run when a validation error occurs deserializing into the object.

  private IActionResult InputErrorHandler(Valigator.ValidationError[] errors)
      => errors.ToUnexpectedError().ToActionResult();

• Add the output error handler. This handler will be run when a validation error occurs serializing objects.

  private IActionResult OutputErrorHandler(ModelError[] errors)
      => errors.ToValidationError().ToActionResult();

Random Things To Move to Better Places

Custom Validations

Examples:

public Data<Option<int>> IntegerValue { get; set; } = Data.Required<int>().Nullable().Assert("A meaningful description", value => value > 1)

Gotchas

1. All properties must have a setter. This setter may be private.