@jsonSchema Directive

The @jsonSchema directive can be used to configure a JSON Schema for the variables of an Operation. This JSON Schema is not only good for input validation, it's also useful for code generation. For example, it's possible to generate a complete type-safe client including forms, just by writing a GraphQL Operation.

This example shows all available arguments for the directive, we'll then break them down, one by one.

mutation (
  $message: String!
    @jsonSchema(
      title: "Message"
      description: "Describe the message"
      pattern: "^[a-zA-Z 0-9]+$"
      commonPattern: EMAIL
      commonPattern: DOMAIN
      minLength: 3
      maxLength: 5
      minimum: 1
      maximum: 1
      exclusiveMaximum: 2
      exclusiveMinimum: 2
      maxItems: 1
      minItems: 1
      multipleOf: 1
      uniqueItems: true
    )
) {
  createPost(message: $message) {
    id
    message
  }
}

The value of both of these keywords MUST be a string.

Both of these keywords can be used to decorate a user interface with information about the data produced by this user interface. A title will preferably be short, whereas a description will provide explanation about the purpose of the instance described by this schema.

The value of this keyword MUST be a string. This string SHOULD be a valid regular expression, according to the ECMA 262 regular expression dialect.

A string instance is considered valid if the regular expression matches the instance successfully. Recall: regular expressions are not implicitly anchored.

The value of this keyword MUST be one of: EMAIL, DOMAIN

A string instance is considered valid if the regular expression of the common pattern matches the instance successfully.

The value of this keyword MUST be a non-negative integer.

A string instance is valid against this keyword if its length is greater than, or equal to, the value of this keyword.

The length of a string instance is defined as the number of its characters as defined by RFC 7159 [RFC7159].

Omitting this keyword has the same behavior as a value of 0.

The value of this keyword MUST be a non-negative integer.

A string instance is valid against this keyword if its length is less than, or equal to, the value of this keyword.

The length of a string instance is defined as the number of its characters as defined by RFC 7159 [RFC7159].

The value of "minimum" MUST be a number, representing an inclusive lower limit for a numeric instance.

If the instance is a number, then this keyword validates only if the instance is greater than or exactly equal to "minimum".

The value of "maximum" MUST be a number, representing an inclusive upper limit for a numeric instance.

If the instance is a number, then this keyword validates only if the instance is less than or exactly equal to "maximum".

The value of "exclusiveMinimum" MUST be number, representing an exclusive lower limit for a numeric instance.

If the instance is a number, then the instance is valid only if it has a value strictly greater than (not equal to) "exclusiveMinimum".

The value of "exclusiveMaximum" MUST be number, representing an exclusive upper limit for a numeric instance.

If the instance is a number, then the instance is valid only if it has a value strictly less than (not equal to) "exclusiveMaximum".

The value of this keyword MUST be a non-negative integer.

An array instance is valid against "minItems" if its size is greater than, or equal to, the value of this keyword.

Omitting this keyword has the same behavior as a value of 0.

The value of this keyword MUST be a non-negative integer.

An array instance is valid against "maxItems" if its size is less than, or equal to, the value of this keyword.

The value of "multipleOf" MUST be a number, strictly greater than 0.

A numeric instance is valid only if division by this keyword's value results in an integer.

The value of this keyword MUST be a boolean.

If this keyword has boolean value false, the instance validates successfully. If it has boolean value true, the instance validates successfully if all of its elements are unique.

Omitting this keyword has the same behavior as a value of false.

@jsonSchema accepts an optional on: argument that might be used to set the JSON schema for an specific field. Given the following type:

input createUserInput {
  id: String!
  email: String!
  name: String!
}

We can use @jsonSchema to set the JSON schema of id using:

mutation ($input: createUserInput! @jsonSchema(pattern: "[0-9]+", on: "id")) {
  users_Create($input) {
    id
    email
    name
  }
}

@jsonSchema can be used multiple times on the same operation, validating data for different fields. Additionally, @jsonSchema can be combined with other directives for injecting or manipulating data like @fromClaim, @injectCurrentDateTime, @injectEnvironmentVariable and @injectGeneratedUUID.