Async-graphql: Introspection query returns type MergedObjectTail without any fields

[frigus02]

Thanks for all your work on async-graphql. We really enjoy working with it.

We use the introspection query to generate a GraphQL schema, which we can share with clients of the API. In version 2.0.5 this doesn't work anymore. Please let me know if I'm doing something wrong 🙂

Expected Behavior

Introspection query returns valid result, which can be used in apps like the GraphQL Playground.

Actual Behavior

The introspection query returns a type without fields for each #[Object] without functions (or where the only function is an entity). This is also the case for merged objects, which are unlikely to have any functions implemented themselves. In this case a type MergedObjectTail without fields is returned.

Apps like the GraphQL Playground seem to validate the schema and then print error messages like this:

Type MergedObjectTail must define one or more fields.

Steps to Reproduce the Problem

1. Create a #[Object] only implementing a single entity function. Similar to this:

   struct Query;
   
   #[Object]
   impl Query {
    #[graphql(entity)]
    async fn get(&self, id: ID) -> String {
      "test".into()
    }
   }
   

2. Request the introspection query result

I made a small example here:
https://github.com/frigus02/test-async-graphql-deterministic-introspection/tree/67c9bb27b61b169118a5be9728b48ee02e3178be

When you run make it:

• Builds the Rust program
• Writes the introspection query result to a file
• Use the graphql node module to validate the schema and print any errors it finds

Specifications

• Version: 2.0.5
• Platform: macOS

[frigus02]

I tried to find out the issue may be in the schema validation. I found https://github.com/graphql/graphql-js/issues/937 and https://github.com/graphql/graphql-spec/issues/568:

• The spec says the field definition for Object types is optional

  Description(opt) type Name ImplementsInterfaces(opt) Directives(const, opt) FieldsDefinition(opt)
  -- https://spec.graphql.org/draft/#sec-Objects

• But the validation rules for objects start with

  1 An Object type must define one or more fields.
  -- https://spec.graphql.org/draft/#sec-Objects.Type-Validation

Not sure what that means for async-graphql. Should it filter out types without fields from the introspection?

[sunli829]

This is a bug, and I am solving it.

[sunli829]

Please upgrade to v2.0.6, this problem has been resolved. 😁

[frigus02]

Super quick, thanks a lot!