directive @provides(fields: _FieldSet!) on FIELD_DEFINITION

The @provides directive is used to annotate the expected returned fieldset from a field on a base type that is guaranteed to be selectable by the gateway. This allows you to expose only a subset of fields from the underlying federated object type to be selectable from the federated schema. Provided fields specified in the directive field set should correspond to a valid field on the underlying GraphQL interface/object type. @provides directive can only be used on fields returning federated extended objects.

Example: We might want to expose only name of the user that submitted a review.

@KeyDirective(FieldSet("id"))
class Review(val id: String) {
  @ProvidesDirective(FieldSet("name"))
  fun user(): User = // implementation goes here
}

@KeyDirective(FieldSet("userId"))
@ExtendsDirective
class User(
  @ExternalDirective val userId: String,
  @ExternalDirective val name: String
)

should generate

type Review @key(fields : "id") {
  id: String!
  user: User! @provides(fields : "name")
}

type User @extends @key(fields : "userId") {
  userId: String! @external
  name: String! @external
}