Issues with introspection query when no Query type is in schema

[mattjohnsonpint]

Consider a schema that contains only mutations:

type Mutation {
  doSomething: Boolean
}

In such cases, it appears that an empty root Query object is being added to the results of the introspection queries:

{
  "data": {
    "__schema": {
      "queryType": { "name": "Query" },
      "mutationType": { "name": "Mutation" },
      "subscriptionType": null,
      "types": [
        {
          "kind": "OBJECT",
          "name": "Query",
          "description": "",
          "fields": null,
          "inputFields": [],
          "interfaces": [],
          "enumValues": null,
          "possibleTypes": []
        },
...

This is good, because (as I learned), the GraphQL spec requires a Query type but you can't define an empty type Query or type Query {} because all object types must have at least one field. Short of adding a fake field that would clutter the schema, having the introspection query tack on a Query object is a good idea!

HOWEVER, I'm getting an error in Postman:

This seems to be caused by "fields": null. As a workaround, I modified our code to patch that to be "fields": [] and the error goes away. (see hypermodeinc/modus#558)

I dug through the GraphQL Go Tools sources, but I really can't seem to find where the Query type is being added. Any ideas? Happy to send a PR if you can point me in the right direction. Thanks.

[devsergiy]

Hi @mattjohnsonpint

Basically, in our case, we anyway will add a Query type with introspection service fields

But right now our introspection generator skips such fields

They could be added and the query would never be empty