[FEATURE] Validation (directive)

[IzumiSy]

Currently, fabrix does not support any form of validation, but for a long run, fabrix is going to support graphql-constraint-spec that for future.

In addition to that, client-side validation is clearly also needed in some cases, so as an initial approach, add field-level validation with directives.

Design

Fabrix provides the new input types for constraints as follows. These fields come partially from graphql-constraint-directive which is an implementation of the spec.

input FabrixFormConstraint {
  """
  String
  """
  minLength: Int
  maxLength: Int
  pattern: String
  format: String
  oneOf: [String]

  """
  Int
  """
  min: Int
  max: Int
  exclusiveMin: Int
  exclusiveMax: Int
  multipleOf: Int
  oneOf: [Int]

  """
  Float
  """
  min: Float
  max: Float
  exclusiveMin: Float
  exclusiveMax: Float
  multipleOf: Float
  oneOf: [Float]
}

Discussion points

The spec, graphql-constraint-spec has not been updated since 7 years ago. I don't have to follow everything with the thing that is way too stale, so need some discussion to decide our own do's and dont's.

• Availability of some rules
  • startsWith, endsWith, contains, notContains: these can be replaced with pattern as well, but error messages of them could be more intuitive to users than pattern. Also, when it comes to customizing error messages with i18n, using pattern does not have enough controllability.
  • equals: pattern can work out for string values as well here. As for Int/Float values, I think that's pretty rare to check if the value has the exact match with the other value as validation.
• Types for format: currently, fabrix internally uses Ajv to implement validator, so the idea for now is just using ajv-formats. It has variety of common string formats, so it looks enough.
• The ways to handle conditional validation and field reference.

Usage

mutation createUser($input: CreateUserInput!) {
  createUser(input: $input)
    @fabrixForm(
      input: [
        { field: "name", constraint: { maxLength: 50 } },
        { field: "email", constraint: { format: "email" } },
      ]
    ) {
    id
  }
}