Why Prohibit Concrete Root Values?

In most cases you won't need to explicitly define the root types Query, Mutation or Subscription since they will be implicitly created if you add fields to them with the @gqlQueryField, @gqlMutationField or @gqlSubscriptionField tags.

However, if you wish to explicitly define one of these types in order to add a description to it, Grats will require that you define it as a type alias of unknown. For example:

/**
 * My great description
 * @gqlType */
type Query = unknown;

Grats forces this constraint because the semantics of the root value is not well defined across GraphQL server implementations. For example, Yoga does not allow you to define a root value, where as other server implementations use a single root value that is shared by all resolvers. Additionally, it's not specified if the root value should be shared by all requests or regenerated for each request.

There are some valid uses for a concrete root value, such as dependency injection, but in general dependency injection can be more easily achieved by using context. If you believe you have a valid use case for a concrete root value, please open an issue.