Interfaces in GraphQL HotChoclate - schema first getting exception-CodePudding

I am trying to implement schema-first in Hot Chocolate and running into SchemaException

I have the below GraphQL Schema

type Query {      
  sites(skip: Int, take: Int): SitesResponse  
}

interface PagedResponse {
  hasNextPage: Boolean!
  hasPreviousPage: Boolean!
  totalCount: Int!
}

type SitesResponse implements PagedResponse {
  items: [Site]
}

type Site {
  siteNumber: String!
  siteName: String!
  siteType: String!
  divisionNumber: Int!
}

Startup

services
.AddGraphQLServer()
.AddDocumentFromFile("GraphQlSchema.graphql")
.AddResolver<RosterResolver>("Query")
.BindRuntimeType<PagedResponse<Site>>("SitesResponse")

Resolver

public class RosterResolver
    {
        public PagedResponse<Site> GetSites(int? skip, int? take)
        {
            return new PagedResponse<Site>
            {
                HasNextPage = false,
                HasPreviousPage = false,
                Items = new List<Site> { new Site { DivisionNumber = 1, SiteName = "test", SiteNumber = "1234", SiteType = "Test" } },
                TotalCount = 1
            };
        }

Result

HotChocolate.SchemaException: For more details look at the `Errors` property.

1. The field `hasNextPage` must be implement by object type `SitesResponse`. (HotChocolate.Types.ObjectType)
2. The field `hasPreviousPage` must be implement by object type `SitesResponse`. (HotChocolate.Types.ObjectType)
3. The field `totalCount` must be implement by object type `SitesResponse`. (HotChocolate.Types.ObjectType)

   at HotChocolate.Configuration.TypeInitializer.Initialize(Func`1 schemaResolver, IReadOnlySchemaOptions options)
   at HotChocolate.SchemaBuilder.Setup.InitializeTypes(SchemaBuilder builder, IDescriptorContext context, IReadOnlyList`1 types, LazySchema lazySchema)
   at HotChocolate.SchemaBuilder.Setup.Create(SchemaBuilder builder, LazySchema lazySchema, IDescriptorContext context)
   at HotChocolate.SchemaBuilder.Create(IDescriptorContext context)
   at HotChocolate.SchemaBuilder.HotChocolate.ISchemaBuilder.Create(IDescriptorContext context)
   at HotChocolate.Execution.RequestExecutorResolver.CreateSchemaAsync(NameString schemaName, RequestExecutorSetup options, RequestExecutorOptions executorOptions, IServiceProvider serviceProvider, TypeModuleChangeMonitor typeModuleChangeMonitor, CancellationToken cancellationToken)
   at HotChocolate.Execution.RequestExecutorResolver.CreateSchemaServicesAsync(NameString schemaName, RequestExecutorSetup options, CancellationToken cancellationToken)
   at HotChocolate.Execution.RequestExecutorResolver.GetRequestExecutorNoLockAsync(NameString schemaName, CancellationToken cancellationToken)
   at HotChocolate.Execution.RequestExecutorResolver.GetRequestExecutorAsync(NameString schemaName, CancellationToken cancellationToken)
   at HotChocolate.Execution.RequestExecutorProxy.GetRequestExecutorAsync(CancellationToken cancellationToken)
   at HotChocolate.AspNetCore.HttpPostMiddleware.HandleRequestAsync(HttpContext context, AllowedContentType contentType)
   at HotChocolate.AspNetCore.HttpPostMiddleware.InvokeAsync(HttpContext context)
   at HotChocolate.AspNetCore.WebSocketSubscriptionMiddleware.InvokeAsync(HttpContext context)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

Is it possible to return a generic class PagedResponse? or do we need to implement a concrete class for each return type? ie: SitesResponse, Entity1Response, Entity2Response, etc etc

CodePudding user response：

The GraphQL spec states that the interface fields have to be repeated on the type.

interface PagedResponse {
  hasNextPage: Boolean!
  hasPreviousPage: Boolean!
  totalCount: Int!
}

type SitesResponse implements PagedResponse {
  hasNextPage: Boolean!
  hasPreviousPage: Boolean!
  totalCount: Int!
  items: [Site]
}

If you look at the schema exception it essentially just tells you that:

The field `hasNextPage` must be implement by object type `SitesResponse`. (HotChocolate.Types.ObjectType)

Interface Specification: https://spec.graphql.org/October2021/#sec-Interfaces

Type Validation Rule: https://spec.graphql.org/October2021/#sec-Objects.Type-Validation