Missing getting "__typename" variants if user doesn't specify it in Union or Interface, but only Type

[ghost]

description

if schema is like this,

query BadQuery {
      badCollection {
          __typename
          ... on BadType {
            name
          }
      }
}

"BadType" causes value: Error("unknown variant BadType, there are no variants", line: 16, column: 52)', if user doesn't specify "BadType" in Union or Interface but only in Type.

Minimal Reproduce: https://github.com/graphql-rust/graphql-client/compare/main...ulwlu:test_multiple_implement?expand=1

Related Issue: https://github.com/graphql-rust/graphql-client/issues/394

Minimal Fix: Just add below in above minimal reproduce.

union Foo = GoodType | BadType

type goodCollection {
  items: [Foo]!
}

type badCollection {
  items: [Foo]!
}

Remarks

This happens here.

https://github.com/graphql-rust/graphql-client/blob/e79e30c1b5ae96048d3fbf071a7dd201502bb4e2/graphql_client_codegen/src/codegen/selection.rs#L146-L165

Because it doesn't run when context is "Object", it will never run context.push_variant. So, it will never run https://github.com/graphql-rust/graphql-client/blob/e79e30c1b5ae96048d3fbf071a7dd201502bb4e2/graphql_client_codegen/src/codegen/selection.rs#L559-L565 correctly.

So it will create only empty enum, and it didn't expect any tag="__typename", so it causes panic.

what i wanna know

Is there any reason why this only accepts interface and union?

if this is not on purpose, i can make pr.