Return a query result without or with a null data field

[zizhengtai]

Hi, how can I return a query result that looks like either of the following from a Kotlin Spring WebFlux server?

1. Errors without data:

{
  "errors": [...]
}

2. Errors with null data:

{
  "data": null,
  "errors": [...]
}

Currently, if I do something like this:

@Component
class FooQuery : Query {
  fun foo(): Foo {
    throw ...
  }
}

I'll get an error complaining that I returned a null result while the return type of the query is specified as Foo!. But according to the GraphQL specs, the nullness should just propagate up and make data null.

[dariuszkuc]

Hello 👋
Take a look at https://opensource.expediagroup.com/graphql-kotlin/docs/schema-generator/execution/exceptions. You might also want to update your schema type to be nullable (i.e. fun foo(): Foo?).

[zizhengtai]

Hi @dariuszkuc , I have tried both of these approaches. Using fun foo(): Foo? causes the result to look like this when an exception is thrown, even if I don't explicitly set the data field:

{
  "data": {    // I want just `"data": null` instead
    "foo": null
  },
  "errors": [...]
}

I've also tried providing my own exception handler, which results in the same behavior anyway. I.e., I'm not able to make the "data" field itself null or completely gone.

[smyrick]

If you throw an exception in your schema code without handling any errors, the data field will be missing

[zizhengtai]

If you throw an exception in your schema code without handling any errors, the data field will be missing

In this case I get another error in the "errors" list that complains about "foo" being null when it's schema is nonnullable. If I make the schema nullable (i.e. fun foo(): Foo?), then "data" gets populated again.

[dariuszkuc]

Indeed, I missed the part of "data": null vs "data" { "foo": null}. Currently it is not possible to have explicit null value for data. This is an optimization from Jackson (https://github.com/ExpediaGroup/graphql-kotlin/blob/master/servers/graphql-kotlin-server/src/main/kotlin/com/expediagroup/graphql/server/types/GraphQLServerRequest.kt#L39).

Do you mind elaborating on your use case and why do you need it?