aws-appsync sdk returns __typename Attribut

[jacekv]

Do you want to request a feature or report a bug?

I want to report a bug.

What is the current behavior?

We use a single Query to request different types of information. In order to distinguish the items returned, the __typename attribute is used. aws-appsync returns and displays the __typename attribute, even it is not in the provided schema.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem.

In order for Graphql to distinguish the items, the __typename attribute is required. In our case, our resolvers are taking care of it and you see that there is no notion of the __typename attribute in the schema. Example schema:

interface News {
    id: String
}

type Post implements News {
    author: String
    text: String
}

type Article implements News {
    author: String
    text: String
    headline: String
}

type NewsList {
    items: [News]
}

type Query {
    listNews(): NewsList
}

and a query would look like this:

query ListNews() {
    listNews() {
        items {
            ... on Article {
                author
                text
                headline
            }
            ... on Post {
                author
                text
            }
        }
    }
}

Response:

{
    data: {
        listNews {
             items: [
                 {
                     "author": "ABC",
                     "text": "Blabla123",
                     "__typename": "Post" # <-- this attribute should not be there
                 },
                 {
                     "author": "ABC",
                     "text": "Blabla123",
                     "Headline": "BLABLA",
                     "__typename": "Article" # <-- this attribute should not be there
                 }
             ]
        }
    }
}

What is the expected behavior?

The expected behavior is, that the __typename attribute is not returned to the client.

Which versions and which environment (browser, react-native, nodejs) / OS are affected by this issue? Did this work in previous versions?

I am using "aws-appsync": "^4.0.0" in Lambda with runtime Nodejs 10.x. Since I am using your sdk for the first time, I haven't tried any other versions.