Cyclic schema giving error as "Error: Schema must contain unique named types but contains multiple types named "Node"."

[hiteshbal91]

I am stucked into bi-directional schema mapping. posts <-> authors.

Following are the two schema we are using.

posts.js // here we are requiring authors.js 

class Post {}
const {
    nodeInterface,
    nodeField
} = nodeDefinitions(
    globalId => {
        const {
            type,
            id
        } = fromGlobalId(globalId);
        // return based on the id
        return DataSource['posts'][0];
    },
    obj => {
        console.log(" : PostType : ", PostType);
        // type to be return 
        return Post;
    }
);
const PostType = new GraphQLObjectType({
    "name": "PostType",
    "description": "Posts type and it's relevant fields",
    "fields": () => ({
        "id": globalIdField('Post'),
        "title": {
            "type": GraphQLString
        },
        "body": {
            "type": GraphQLString
        },
        "author": {
            "type": AuthorsConnection,
            "resolve": (parent, argument, root, currentSdl) => {
                console.log("v1, v2, v3, v4  :", parent);
                if (parent.author)
                    return connectionFromArray(DataSource['authors'], {})
                return [];
            }
        }
    }),
    isTypeOf: Post,
    interfaces: [nodeInterface]
});
const {
    connectionType: PostsConnection,
    edgeType: GQLPostEdge
} = connectionDefinitions({
    name: "Post",
    nodeType: PostType
});
module.exports = exports = {
    PostType,
    PostsConnection,
    schema: {
        post: nodeField,
        posts: {
            type: PostsConnection,
            resolve: (root, v2, v3) => {
                return connectionFromArray(DataSource['posts'], {});
            }
        }
    }
};

authors.js // here we have required posts.js
const {
    PostType,
    PostsConnection
} = require('./posts');

class Author {}

const {
    nodeInterface,
    nodeField
} = nodeDefinitions(
    globalId => {
        const {
            type,
            id
        } = fromGlobalId(globalId);
        // return based on the id
        return DataSource['authors'][0];
    },
    obj => {
        console.log(" : Authorype : ", Authorype);
        // type to be return 
        return Author;
    }
);

const AuthorType = new GraphQLObjectType({
    "name": "AuthorType",
    "description": "Author type and it's relevant fields",
    "fields": () => ({
        "id": globalIdField('Author'),
        "firstName": {
            "type": GraphQLString
        },
        "lastName": {
            "type": GraphQLString
        },
        authorPosts: {
            type: PostsConnection,
            resolve: (parent, args, root, context) => {
                return connectionFromArray(DataSource['posts'], {});
            }
        }
    }),
    isTypeOf: null,
    interfaces: [nodeInterface]
});

const {
    connectionType: AuthorsConnection,
    edgeType: GQLAuthorEdge
} = connectionDefinitions({
    name: "Author",
    nodeType: AuthorType
});

module.exports = exports = {
    AuthorType,
    AuthorsConnection,
    schema: {
        author: nodeField,
        authors: {
            type: AuthorsConnection,
            resolve: (root, v2, v3) => {
                return connectionFromArray(DataSource['authors'], {});
            }
        }
    }
};

Once I merge above schema for GraphQL I am getting following error.

Error: Schema must contain unique named types but contains multiple types named "Node".

I tried to debugged this issue, following is I observed following.

• Once I change "authors" field from posts schema to other than "AuthorsConnection" it starts working.
• Or if removed "authors" field from posts schema it starts working.

Please let me know what is issue here, is it relevant to nodeDefinitions function?

[IvanGoncharov]

You should share the Node interface between schemas, e.g. extract it into a separate file.